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1.
Mohanty, Nitya Prakash.
The invasive Indian bullfrog Hoplobatrachus tigerinus on the Andaman Islands : evaluating drivers of distribution, density, and trophic impact of an early stage invader.
Degree: PhD, Botany and Zoology, 2019, Stellenbosch University
URL: http://hdl.handle.net/10019.1/106030 
► ENGLISH ABSTRACT: The global spread of humans and their activities change movement patterns of other species, by limiting or enhancing their movement and consequently their…
(more)
▼ ENGLISH ABSTRACT: The global spread of humans and their activities change movement patterns of other species, by limiting or enhancing their movement and consequently their distribution. Biological invasions occur when species are moved beyond their natural range by human activities to a new range, where the species reproduce and spread. These biogeographic changes now occur with rapidity on large scales due to accelerating global trade and transport. Amphibians are an emerging group of invaders, with increasing global frequency of invasive populations. Invasive amphibians have considerable ecological impact on the recipient system mediated through toxicity, competition, predation, and probable disease transmission. The level of ecological impact by invasive amphibians is comparable to that of invasive fish and birds. However, only a limited number of species have been well-studied for their invasion dynamics, limiting understanding and management.
The Indian bullfrog Hoplobatrachus tigerinus, a large dicroglossid frog (snout to vent length: up to 160 mm), is native to the Indian sub-continent. Despite the high likelihood of invasion success for the bullfrog, based on species-traits and human-interaction, its invasion process has not been assessed. This study aimed to understand four major aspects of the Indian bullfrog’s invasion on the Andaman Islands, where it has recently been introduced: i) distribution and dispersal, ii) impact of adults iii) impact of carnivorous tadpoles, and iv) invasion dynamics and efficacy of potential management strategies. Finally, the thesis aimed to assess v) the bullfrog’s global invasion potential and status of all extra-limital populations.
I used a novel approach to reconstruct the Indian bullfrog invasion of the Andaman Islands, combining public surveys and field surveys in a formal analytical framework. The bullfrog occurred in at least 62% of the sampled sites spread over six islands, a dramatic increase to the previously known invaded range. The bullfrog was most likely introduced in early 2000s, and its exponential expansion has occurred since 2009. ‘Contaminants’ of fish culture trade and intentional ‘release’ were reported to be the primary pathways of introduction and post-introduction dispersal, facilitating introductions from the Indian mainland and inter-island transfers. The use of public surveys in a systematic framework adds a complimentary tool to the existing methods for reconstructing invasions.
I assessed the diet of the invasive Indian bullfrog and two co-occurring native frogs (genus Limnonectes and Fejervarya) to assess the impact of adult bullfrogs. Vertebrates made up the majority of the bullfrog’s diet in terms of volume, whereas, invertebrates were numerically dominant. I only found a significant dietary overlap between the bullfrog and individuals of the genus Limnonectes. Prey size electivity was governed by body size of the three species. This intensive study on a hitherto unassessed genus of invasive amphibians contributes to the knowledge on…
Advisors/Committee Members: Measey, John, Stellenbosch University. Faculty of Science. Dept. of Botany and Zoology..
Subjects/Keywords: Biological invasions; Trophic ecology; Species distribution modelling; Indian bullfrog (Hoplobatrachus tigerinus) – Andaman Islands; UCTD
…Stellenbosch University https://scholar.sun.ac.za
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menslike… …skep wat oordraagbaar is aan
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ander… …biologiese indringers en populasie-ekologie in die algemeen.
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Botany and Zoology, Stellenbosch University… …Chapter 2 to Chapter 6, to
the thesis and linkage among chapters.
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Stellenbosch University…
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APA (6th Edition):
Mohanty, N. P. (2019). The invasive Indian bullfrog Hoplobatrachus tigerinus on the Andaman Islands : evaluating drivers of distribution, density, and trophic impact of an early stage invader. (Doctoral Dissertation). Stellenbosch University. Retrieved from http://hdl.handle.net/10019.1/106030
Chicago Manual of Style (16th Edition):
Mohanty, Nitya Prakash. “The invasive Indian bullfrog Hoplobatrachus tigerinus on the Andaman Islands : evaluating drivers of distribution, density, and trophic impact of an early stage invader.” 2019. Doctoral Dissertation, Stellenbosch University. Accessed January 26, 2021.
http://hdl.handle.net/10019.1/106030.
MLA Handbook (7th Edition):
Mohanty, Nitya Prakash. “The invasive Indian bullfrog Hoplobatrachus tigerinus on the Andaman Islands : evaluating drivers of distribution, density, and trophic impact of an early stage invader.” 2019. Web. 26 Jan 2021.
Vancouver:
Mohanty NP. The invasive Indian bullfrog Hoplobatrachus tigerinus on the Andaman Islands : evaluating drivers of distribution, density, and trophic impact of an early stage invader. [Internet] [Doctoral dissertation]. Stellenbosch University; 2019. [cited 2021 Jan 26].
Available from: http://hdl.handle.net/10019.1/106030.
Council of Science Editors:
Mohanty NP. The invasive Indian bullfrog Hoplobatrachus tigerinus on the Andaman Islands : evaluating drivers of distribution, density, and trophic impact of an early stage invader. [Doctoral Dissertation]. Stellenbosch University; 2019. Available from: http://hdl.handle.net/10019.1/106030
2.
Treasure, Anne M. (Anne Margaret).
Climate change and invasion impacts in the sub-Antarctic.
Degree: PhD, Botany and Zoology, 2012, Stellenbosch University
URL: http://hdl.handle.net/10019.1/20010
► ENGLISH ABSTRACT: Climate change and biological invasions are major threats to biodiversity. In particular, these threats are predicted to influence terrestrial systems in the sub-Antarctic,…
(more)
▼ ENGLISH ABSTRACT: Climate change and biological invasions are major threats to biodiversity. In particular,
these threats are predicted to influence terrestrial systems in the sub-Antarctic, where
significant ecosystem responses to both have already been seen. In this thesis, the
sub-Antarctic Prince Edward Island group is used as a model system in which to investigate
key questions relating to climate change and invasive species impacts. The island group
comprises two islands, Marion (MI) and Prince Edward (PEI), both of which are
experiencing rapid warming, yet have different invasive assemblages and in consequence
are experiencing different impacts.
Variation in the patterns of invasive species richness and abundance and their
underlying causes are matters of considerable ecological and conservation significance.
While an increase in thermal energy availability typically results in an increase in species
richness, the mechanisms underlying these patterns are poorly understood. In Chapter 2 of
this thesis, these relationships are explored for springtails, an important component of the
soil fauna on Marion Island. Energy explains a large amount of the spatial variation in
indigenous and invasive springtail species richness. Disturbance thresholds and stressful
temperatures are more important than increased population sizes in determining this
variation in species richness. As both indigenous and invasive springtail species richness
and abundance are strongly related to temperature, a warming climate could have
far-reaching consequences for these organisms. In particular, invasive species are predicted
to be at an advantage relative to indigenous species under warming conditions. One species where this seems especially likely, given its physiological responses to
experimental warming and drying, is the large invasive tomocerid, Pogonognathellus
flavescens. Determining whether this will be the case depends on understanding the
factors underlying its range limits and abundance structure. Moreover, few studies have
sought to distinguish the causal basis of abundance structure and range limits, particularly
for invasive species. Thus, in Chapter 3, local microclimate variables and physiological
tolerances of the invasive springtail, P. flavescens (a habitat generalist), are examined. The
results suggest that the species should be widely distributed across a range of habitats on
MI. However, the springtail is restricted to indigenous Poa cookii tussock grassland habitats
in the southeast. The current range limits are set by dispersal limitation (i.e. contingent absences) whilst abundance structure is a function of variation in soil substrate quality.
However, over time, the widening distribution of P. cookii, as a consequence of a major
management intervention (the eradication of feral cats), may enable P. flavescens to
colonise all suitable areas.
In Chapter 4, the focus changes to what has been considered the third major
response to climate change, along with range and phenological…
Advisors/Committee Members: Chown, Steven L., Stellenbosch University. Faculty of Science. Dept. of Botany and Zoology..
Subjects/Keywords: Zoology; Sub-Antarctic Regions – Climate change; Invasive species – Sub-Antarctic Regions
…Stellenbosch University http://scholar.sun.ac.za
unless the prediction of an increase of… …species to new areas all the more important.
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Stellenbosch University http… …wees oor 'n
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verskeidenheid van… …ondersoek is op ME,
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die meeste fenotipiese… …150
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Chapter 5 – Phenotypic…
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APA (6th Edition):
Treasure, A. M. (. M. (2012). Climate change and invasion impacts in the sub-Antarctic. (Doctoral Dissertation). Stellenbosch University. Retrieved from http://hdl.handle.net/10019.1/20010
Chicago Manual of Style (16th Edition):
Treasure, Anne M (Anne Margaret). “Climate change and invasion impacts in the sub-Antarctic.” 2012. Doctoral Dissertation, Stellenbosch University. Accessed January 26, 2021.
http://hdl.handle.net/10019.1/20010.
MLA Handbook (7th Edition):
Treasure, Anne M (Anne Margaret). “Climate change and invasion impacts in the sub-Antarctic.” 2012. Web. 26 Jan 2021.
Vancouver:
Treasure AM(M. Climate change and invasion impacts in the sub-Antarctic. [Internet] [Doctoral dissertation]. Stellenbosch University; 2012. [cited 2021 Jan 26].
Available from: http://hdl.handle.net/10019.1/20010.
Council of Science Editors:
Treasure AM(M. Climate change and invasion impacts in the sub-Antarctic. [Doctoral Dissertation]. Stellenbosch University; 2012. Available from: http://hdl.handle.net/10019.1/20010
3.
Nkomo, Mpumelelo.
Metabolomic profiling and micropropagation of Salvia africanalutea L. potent against Fusarium verticillioides.
Degree: PhD, Botany and Zoology, 2014, Stellenbosch University
URL: http://hdl.handle.net/10019.1/96135
► ENGLISH ABSTRACT: Salvia africana lutea is one of 26 Sage species indigenous to Southern Africa from a total of 900 worldwide. The genus Salvia belongs…
(more)
▼ ENGLISH ABSTRACT: Salvia africana lutea is one of 26 Sage species indigenous to Southern Africa from a total of 900
worldwide. The genus Salvia belongs to the Lamiaceae family. Labeled a ‘broad spectrum remedy’ S.
africana lutea amongst other sage species is medicinally important. Reports are many highlighting its
benefits, which include from alleviating coughs and colds to gynaecological complaints. Studies have
revealed in vitro antimicrobial, anti-cancer and antioxidant activity.
Plant secondary metabolites fundamentally have a strong bearing on the phytochemical activities a
plant may possess. Consequently the environment indirectly affects the phytochemical properties as it
influences the variation in the plant metabolome via plant-environment interactions. Five S. africana
lutea plant populations, within the Western Cape province of South Africa were sampled and
chemotypes and bioactivity tested. Four populations were wild growing in protected areas namely;
Brackenfell, Koeberg, Silwerstroomstrand and Yzerfontein, while the fifth was a garden growing
population from
Stellenbosch.
Using gas chromatography hyphenated with mass spectrometry (GC-MS), compounds such as
monosaccharides, carboxylic acids and fatty acids were detected. Variation of compounds identified
with 80% certainty was compared across all populations.
Stellenbosch population showed some
compounds that were not present in the other four sites. These compounds were namely; propanoic
acid, rythronic acid, 2-keto-1-gluconic acid and 1,3-dibromobicyclon, while this population also did not
have xylitol that was detected in all the other four populations. To consolidate the GC-MS findings, analysis on the metabolite profiles (utilizing liquid
chromatography linked with mass spectrometry (LC-MS) and nuclear magnetic resonance (1H NMR))
was done. Principal component analysis (PCA) was applied to the NMR data. The partial least squaresdiscriminant
analysis (PLS-DA) was used to integrate LC-MS and NMR data sets. All statistics were
performed with the SIMCA-P+ 12.0 software. By integrating LC-MS and 1H NMR analyses, large
chemotype differences leading to samples grouping by site, suggested strong plant-environment
interactions as factors influencing metabolite composition. Signals distinguishing the
Stellenbosch
profile were in the aromatic part of the 1H NMR spectra. Antimicrobial activity was tested against two Fusarium species. Fusarium is a plant pathogenic species
that causes large agricultural losses particularly in the maize crop, one of the staple foods in the African
continent. Some species also produce mycotoxins in infected crop and lead to a significant increase in
the risk factor of cancers when contaminated foods are consumed. Four high-mycotoxin producing
strains from two species F. verticillioides (MRC 826 and MRC 8267); F. proliferatum (MRC 7140 and
MRC 6809) were utilized in all in vitro antifungal assays in this study. A preliminary assay using
dichloromethane: methanol (1:1 v/v) crude plant extracts of the…
Advisors/Committee Members: Makunga, Nokwanda P., Katerere, David R., Stellenbosch University. Faculty of Science. Dept. of Botany and Zoology..
Subjects/Keywords: Botany; Dissertations – Botany
…Stellenbosch University http://scholar.sun.ac.za
Table of Contents
Declaration by… …13
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Chapter Three… …54
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4.5
Acknowledgements… …83
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List of Figures
FIGURE 2.1… …65
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Stellenbosch University http://scholar.sun.ac.za
List of Tables
TABLE 3.1 MINIMUM…
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APA (6th Edition):
Nkomo, M. (2014). Metabolomic profiling and micropropagation of Salvia africanalutea L. potent against Fusarium verticillioides. (Doctoral Dissertation). Stellenbosch University. Retrieved from http://hdl.handle.net/10019.1/96135
Chicago Manual of Style (16th Edition):
Nkomo, Mpumelelo. “Metabolomic profiling and micropropagation of Salvia africanalutea L. potent against Fusarium verticillioides.” 2014. Doctoral Dissertation, Stellenbosch University. Accessed January 26, 2021.
http://hdl.handle.net/10019.1/96135.
MLA Handbook (7th Edition):
Nkomo, Mpumelelo. “Metabolomic profiling and micropropagation of Salvia africanalutea L. potent against Fusarium verticillioides.” 2014. Web. 26 Jan 2021.
Vancouver:
Nkomo M. Metabolomic profiling and micropropagation of Salvia africanalutea L. potent against Fusarium verticillioides. [Internet] [Doctoral dissertation]. Stellenbosch University; 2014. [cited 2021 Jan 26].
Available from: http://hdl.handle.net/10019.1/96135.
Council of Science Editors:
Nkomo M. Metabolomic profiling and micropropagation of Salvia africanalutea L. potent against Fusarium verticillioides. [Doctoral Dissertation]. Stellenbosch University; 2014. Available from: http://hdl.handle.net/10019.1/96135
4.
Mnisi, Bongani.
The Iingcungcu Project : restoring nectar feeding birds, building biodiversity leadership.
Degree: MSc, Botany and Zoology, 2017, Stellenbosch University
URL: http://hdl.handle.net/10019.1/101127
► ENGLISH ABSTRACT: Plant-pollinator interactions are threatened by habitat fragmentation and little is being done to mitigate its varying impacts. Thus the Iingcungcu study put together…
(more)
▼ ENGLISH ABSTRACT: Plant-pollinator interactions are threatened by habitat fragmentation and little is being done to mitigate its varying impacts. Thus the Iingcungcu study put together three chapters 1) aiming to establish a methodology to establish ecological corridors linking two protected areas using high school gardens as stepping stones planted with nectar producing plants; 2) Have nectar-feeding birds returned to restored sites?; 3) Did the study manage to nurture future leaders for biodiversity?
The methodology included setting up a nectar producing and bird-pollinated plant species list for the Cape Floristic Region (CFR); criteria for establishment of ecological corridors and another for selection of suitable plants for planting at high schools; selection of suitable plants for planting within the study area. This chapter concludes with a communication and a media strategy used to communicate the study progress.
The results following bird observations suggest that planting suitable nectar producing plants can restore nectar feeding birds, thus restoring plant-pollinator networks. An upward trend in bird abundance was observed on the two species i.e. Zosterops virens (Cape white-eye) and Cinnyris chalybeus (Southern double-collard sunbird).
Furthermore, the results following interaction with grade 10 learners showed an increasing trend over time in the experimental group especially in their responses to one of the grouped questions that tested the knowledge variable. This concludes that there was a significant statistical interaction between the two variables Period (time) and Treatment.
I found that learners are always eager to engage in new projects to learn new things and that their attitudes can change over time towards biodiversity when engaged in environmental education projects.
Restorative efforts on a landscape scale, especially in urban ecosystems, can be best achieved when ecologists begin working together with social scientists. Biodiversity will continue its perilous path if it does not consider humanity its biggest partner in perpetual existence.
AFRIKAANSE OPSOMMING: Plant-bestuiwer interaksies word bedreig deur habitat fragmentasie en min word gedoen om die verskeidenheid gevolge te versag. Gevolglik stel die Iingcungcu studie drie hoofstukke saam gestel 1) poog om 'n metodologie daar te stel om ekologiese korridors tussen twee beskermde gebiede te vestig met Hoërskool tuine beplant met nektar-produserende plante, as ‘n voël-vriendelike korridor; 2) het nektar etende voëls teruggekeer na areas wat gerestoureer is?; 3) het die studie dit reggekry om toekomstige leiers vir biodiversiteit te kweek?
Die metodologie sluit in die opstel van ‘n nektar-produserende en voëlbestuifde plantspesies lys vir die Kaapse Floristiese Streek (KFS); kriteria vir die vestiging van ekologiese korridors en 'n ander vir seleksie van geskikte plante vir aanplanting by hoërskole; seleksie van geskikte plante vir aanplanting binne die studie area. Hierdie hoofstuk sluit af met 'n kommunikasie en 'n media…
Advisors/Committee Members: Pauw, Anton, Geerts, Sjirk, Stellenbosch University. Faculty of Science. Dept. of Botany and Zoology..
Subjects/Keywords: Plant-pollinators; Iingcungcu Project; Birds – Feeding and feeds; Nectar-feeding birds – Ecology; Birds, Attracting of
…Stellenbosch University https://scholar.sun.ac.za
3.8.
References… …103
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1. Chapter 1: A general… …x28;Malachite sunbirds) as the sole pollinator for a group
1
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2
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undertaken, as distances… …Stellenbosch University https://scholar.sun.ac.za
1.2. Study aims
The study focuses on the…
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APA (6th Edition):
Mnisi, B. (2017). The Iingcungcu Project : restoring nectar feeding birds, building biodiversity leadership. (Masters Thesis). Stellenbosch University. Retrieved from http://hdl.handle.net/10019.1/101127
Chicago Manual of Style (16th Edition):
Mnisi, Bongani. “The Iingcungcu Project : restoring nectar feeding birds, building biodiversity leadership.” 2017. Masters Thesis, Stellenbosch University. Accessed January 26, 2021.
http://hdl.handle.net/10019.1/101127.
MLA Handbook (7th Edition):
Mnisi, Bongani. “The Iingcungcu Project : restoring nectar feeding birds, building biodiversity leadership.” 2017. Web. 26 Jan 2021.
Vancouver:
Mnisi B. The Iingcungcu Project : restoring nectar feeding birds, building biodiversity leadership. [Internet] [Masters thesis]. Stellenbosch University; 2017. [cited 2021 Jan 26].
Available from: http://hdl.handle.net/10019.1/101127.
Council of Science Editors:
Mnisi B. The Iingcungcu Project : restoring nectar feeding birds, building biodiversity leadership. [Masters Thesis]. Stellenbosch University; 2017. Available from: http://hdl.handle.net/10019.1/101127
5.
Van Niekerk, Sandy Eve.
A systematic review of the so-called cosmopolitan polydorid Polydora hoplura Claparede, 1869 (Polychaeta: Spionidae) on the South African coast.
Degree: MSc, Botany and Zoology, 2014, Stellenbosch University
URL: http://hdl.handle.net/10019.1/95746
► ENGLISH ABSTRACT: Introduction: Polydora hoplura is considered a cosmopolitan or alien species on the South African coast and is an important pest affecting farmed abalone…
(more)
▼ ENGLISH ABSTRACT: Introduction: Polydora hoplura is considered a cosmopolitan or alien species on the South
African coast and is an important pest affecting farmed abalone and oysters in the region. The
first description of P. hoplura by Day (1954) on the South African coast is not
comprehensive, and the documentation provides no relevant species-specific morphological
information. Regional sampling conducted for the present study revealed that P. hoplura
varied intraspecifically and consisted of at least four distinct morphotypes that may
potentially represent different species that may warrant redescription. By combining
traditional taxonomic methods with molecular techniques, the following questions were
addressed: 1) Do the morphotypes of P. hoplura represent a single species on the South
African coast? and 2) Are the South African representatives of P. hoplura conspecific to
those collected globally? In addition, the study included a literature review with the aim to
provide a brief history of the species to assess its cosmopolitanism.
Materials and methods: Newly sampled specimens used in the morphological observations
were compared with specimens from private collections and museum material. Traditional
taxonomic characteristics were used to distinguish the four morphotypes, and these included
morphological features, pigmentation patterns, aspects of reproduction and habitat
preference. A cluster analysis was performed to assess the validity of the morphotypes.
Furthermore, these morphotypes were also tested for potential genetic differentiation using
both mitochondrial (Cytochrome b) and nuclear (28S) gene fragments. To gain preliminary insights into the level of global geographic genetic variation, South African specimens used
in the molecular analysis were compared to a few specimens collected in New Zealand. Results: Genetic data obtained from mitochondrial DNA and nuclear DNA failed to
differentiate the four morphotypes, suggesting that P. hoplura represented a single
morphologically polymorphic species on the South African coast.
Morphology: Morphotypes 1–3 were recognised as adult forms of the species, while
morphotype 4 represented the first record of a juvenile form of the species.
Pigmentation patterns: Morphotype 1 was characterised by the presence of dark pigmentation
in the anterior region and morphotypes 2 and 3 by the absence of pigmentation. Morphotype
4 had distinct pigmentation that resembled that of late-stage larvae.
Aspects of reproduction: P. hoplura is poecilogenous, producing both planktotrophic and
adelphophagic larvae. Late-stage adelphophagic larvae are morphologically similar to larvae
at the same stage from a previous study conducted by Wilson (1928).
Habitat preferences: The cluster analysis and genetic investigation both showed that the
species was not strictly host specific since individuals collected from abalone, oysters,
scallops and sand showed genetic ‘panmixia’. Conclusions: Different P. hoplura morphotypes collected along the South…
Advisors/Committee Members: Simon, Carol, Matthee, Conrad, Stellenbosch University. Faculty of Science. Dept. of Botany and Zoology..
Subjects/Keywords: Abalone – Diseases and pests; Oysters – Diseases and pests; Polydora hoplura Claparède, 1869 (Polychaeta: Spionidae) – Research; Morphologically polymorphic species; Aquaculture – South Africa; UCTD
…Stellenbosch University http://scholar.sun.ac.za
Table of contents
Declaration
i… …spines
32
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2.5 Molecular methodology
34… …Conclusions
99
References
101
Appendices
112
2
Stellenbosch University http… …3
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Table 4.2
Published morphological… …Zealand
4
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List of figures
Figure 2.1
Map…
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APA ·
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APA (6th Edition):
Van Niekerk, S. E. (2014). A systematic review of the so-called cosmopolitan polydorid Polydora hoplura Claparede, 1869 (Polychaeta: Spionidae) on the South African coast. (Masters Thesis). Stellenbosch University. Retrieved from http://hdl.handle.net/10019.1/95746
Chicago Manual of Style (16th Edition):
Van Niekerk, Sandy Eve. “A systematic review of the so-called cosmopolitan polydorid Polydora hoplura Claparede, 1869 (Polychaeta: Spionidae) on the South African coast.” 2014. Masters Thesis, Stellenbosch University. Accessed January 26, 2021.
http://hdl.handle.net/10019.1/95746.
MLA Handbook (7th Edition):
Van Niekerk, Sandy Eve. “A systematic review of the so-called cosmopolitan polydorid Polydora hoplura Claparede, 1869 (Polychaeta: Spionidae) on the South African coast.” 2014. Web. 26 Jan 2021.
Vancouver:
Van Niekerk SE. A systematic review of the so-called cosmopolitan polydorid Polydora hoplura Claparede, 1869 (Polychaeta: Spionidae) on the South African coast. [Internet] [Masters thesis]. Stellenbosch University; 2014. [cited 2021 Jan 26].
Available from: http://hdl.handle.net/10019.1/95746.
Council of Science Editors:
Van Niekerk SE. A systematic review of the so-called cosmopolitan polydorid Polydora hoplura Claparede, 1869 (Polychaeta: Spionidae) on the South African coast. [Masters Thesis]. Stellenbosch University; 2014. Available from: http://hdl.handle.net/10019.1/95746
6.
Albertus, Randal Marius Colin.
Ecotoxicity and environmental fate of diesel and diesel blends produced by Sasol’s Fischer-Tropsch processes using natural gas and coal as feedstock as well as biodiesel and biodiesel blends.
Degree: PhD, Botany and Zoology, 2012, Stellenbosch University
URL: http://hdl.handle.net/10019.1/71807
► ENGLISH ABSTRACT: World crude oil demand and production is set to increase in the long term and is projected to increase from 82 barrels per…
(more)
▼ ENGLISH ABSTRACT: World crude oil demand and production is set to increase in the long term and is projected to increase from 82 barrels per day in 2007 to an estimated 104 million barrels per day in 2030 according to the International Energy Agency. The environmental challenges posed by the current and projected increased future fuel use, with specific reference to air, aquatic and terrestrial impact, are driving producers and legislators to change fuel specifications and consequently fuel properties to be less harmful to the environment. Traditionally transportation fuels are produced through crude oil refining but in South Africa more than one third of the liquid fuels are produced synthetically through catalytic conversion of gassified coal via the Fischer-Tropsch process by Sasol. Diesel from syncrude is referred to as synthetic diesel and the refiner must blend various hydrocarbon streams, effectively tailoring the diesel to its final composition. Biodiesel from renewable sources like vegetable oils is considered environmentally more acceptable than petrodiesel because of its high biodegradability in the environment, lower sulphur and aromatic hydrocarbon content as well as lowered particulate content in the exhaust emissions. The present research was aimed at evaluating whether the composition of diesels derived from different feed stocks, that included coal, natural gas, crude oil and soybean oil, would influence its biodegradability and ecotoxicity. Acute aquatic tests that included freshwater fish, crustaceans, algae and marine bacteria were used to determine the acute toxicity of diesels. In addition, quantitative structure activity relationship models were used to estimate the biodegradation and ecotoxicity properties of the diesels in an attempt to develop a cost effective tool to determine those properties. The results indicated that the 2-D GC technique quantitatively and qualitatively identified the hydrocarbon constituents in the diesels. The relevance of using the 2-D GC technique was in identifying and quantifying the hydrocarbon breakdown products and being used in a mass balance to confirm the potential biological breakdown processes of the materials used in the present study. The differences in theoretical oxygen demand (ThOD) of the different experimental diesel blends using various blending materials and biodiesel, emphasised and confirmed the importance of calculating the ThOD for the respective blending materials when measuring the biodegradation rates. Furthermore, the biodegradation hierarchy of Pitter and Chudoba (1990) in order of decreasing biodegradability: alkanes > branched alkanes > cyclo-alkanes > aromatic hydrocarbons, could be expanded to include FAME: FAME > alkanes > branched alkanes > cyclo-alkanes > aromatic hydrocarbons. The biochemical pathways identified for the biodegradation of all the diesels was enzyme-enhanced β-oxidation. The present research also indicated that biodiesel addition to crude-derived diesels to increase the density to within the current required…
Advisors/Committee Members: Reinecke, A. J., Phillips, L. G., Stellenbosch University. Faculty of Science. Dept. of Botany and Zoology..
Subjects/Keywords: Zoology; Dissertations – Zoology; Botany and Zoology
…Stellenbosch University http://scholar.sun.ac.za
Acknowledgements
Specials thanks to… …professional career.
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Table of Contents
PAGE… …Inhibition Test
2.5. Quantitative structure-activity relationship
24
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Stellenbosch University… …food security
4.8. Energy security
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101
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List of Figures
TITLE
Figure 1
CAPTION
PAGE
A…
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APA (6th Edition):
Albertus, R. M. C. (2012). Ecotoxicity and environmental fate of diesel and diesel blends produced by Sasol’s Fischer-Tropsch processes using natural gas and coal as feedstock as well as biodiesel and biodiesel blends. (Doctoral Dissertation). Stellenbosch University. Retrieved from http://hdl.handle.net/10019.1/71807
Chicago Manual of Style (16th Edition):
Albertus, Randal Marius Colin. “Ecotoxicity and environmental fate of diesel and diesel blends produced by Sasol’s Fischer-Tropsch processes using natural gas and coal as feedstock as well as biodiesel and biodiesel blends.” 2012. Doctoral Dissertation, Stellenbosch University. Accessed January 26, 2021.
http://hdl.handle.net/10019.1/71807.
MLA Handbook (7th Edition):
Albertus, Randal Marius Colin. “Ecotoxicity and environmental fate of diesel and diesel blends produced by Sasol’s Fischer-Tropsch processes using natural gas and coal as feedstock as well as biodiesel and biodiesel blends.” 2012. Web. 26 Jan 2021.
Vancouver:
Albertus RMC. Ecotoxicity and environmental fate of diesel and diesel blends produced by Sasol’s Fischer-Tropsch processes using natural gas and coal as feedstock as well as biodiesel and biodiesel blends. [Internet] [Doctoral dissertation]. Stellenbosch University; 2012. [cited 2021 Jan 26].
Available from: http://hdl.handle.net/10019.1/71807.
Council of Science Editors:
Albertus RMC. Ecotoxicity and environmental fate of diesel and diesel blends produced by Sasol’s Fischer-Tropsch processes using natural gas and coal as feedstock as well as biodiesel and biodiesel blends. [Doctoral Dissertation]. Stellenbosch University; 2012. Available from: http://hdl.handle.net/10019.1/71807
7.
Broeckhoven, Chris.
Causes and consequences of body armour in the group-living lizard, Ouroborus cataphractus (Cordylidae).
Degree: PhD, Botany and Zoology, 2015, Stellenbosch University
URL: http://hdl.handle.net/10019.1/96602
► ENGLISH ABSTRACT: Cordylidae is a family of predominantly rock-dwelling sit-and-wait foraging lizards endemic to southern Africa. The significant variation in spine length and extent of…
(more)
▼ ENGLISH ABSTRACT: Cordylidae is a family of predominantly rock-dwelling sit-and-wait foraging lizards endemic to southern Africa. The significant variation in spine length and extent of osteoderms among taxa makes the family an excellent model system for studying the evolution of body armour. Specifically, the Armadillo lizard (Ouroborus cataphractus) offers an ideal opportunity to investigate the causes and consequences of body armour. Previous studies have hypothesised that high terrestrial predation pressure, resulting from excursions to termite foraging ports away from the safety of the shelter, has led to the elaboration of body armour and a unique tail-biting behaviour. The reduction in running speed associated with heavy body armour, in turn, appears to have led to the evolution of group-living behaviour to lower the increased aerial predation risk.
In this thesis, a comparative and integrative approach is used to provide more insight into the conditions under which body armour could have evolved in O. cataphractus and the consequences of body armour for life-history traits. Chapter 2 attempts to investigate how competitive and predatory pressures affect the activity patterns of O. cataphractus. Analysis of activity patterns, obtained via remote camera trapping techniques, show low levels of activity during summer in O. cataphractus, resulting from increased competition for food and high predation pressure. In contrast, a shift in activity to spring, when food availability is relatively high, appears to override the negative effects of body armour and group-living behaviour in O. cataphractus. Chapter 3 tests the hypothesis that body armour serves as protection against attacks from predators during foraging excursions away from the safety of the shelter. The relatively high skin toughness, due to the presence of thick osteoderms in the dermis, protects O. cataphractus against most terrestrial predators, while the skin toughness values for other cordylid lizards are well-below the bite forces of potential mammalian predators.
The remaining chapters focus strongly on the feeding behaviour of O. cataphractus and how it is linked to body armour. Chapter 4 investigates the consequences of a reduction in running speed for the diet and tests for the presence of compensatory alternative performance capacities (i.e. increased bite force or jaw closing velocity). A comparative phylogenetic analysis shows that the possession of body armour affects the proportion of evasive prey items that can be included into the diet, thereby restricting the prey spectrum of heavily armoured taxa, such as O. cataphractus, to slow-moving prey (e.g. Coleoptera). Although the results indicate a relatively high bite force in O. cataphractus, the primary selection pressure seems to be tail-biting behaviour, rather than the consumption of hard-bodied Coleoptera (Chapter 5). Bite force, however, trades-off with jaw closing velocity in lizards. A novel lingual prehension mode, exclusive to O. cataphractus (Chapter 6) appears to have evolved…
Advisors/Committee Members: Mouton, P. le Fras N., Stellenbosch University. Faculty of Science. Dept. of Botany and Zoology..
Subjects/Keywords: Armadillo lizard – Causes and consequences of body armour; Armadillo lizard – Feeding behaviour; Antipredator morphology; Girdled lizards; Cordylidae – Southern Africa; UCTD
…Stellenbosch University https://scholar.sun.ac.za
MATERIALS AND METHODS… …OUROBORUS CATAPHRACTUS AND KARUSASAURUS POLYZONUS
vii
Stellenbosch University https… …111
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CHAPTER 7… …128-150
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LIST OF FIGURES
Figure 2.1… …34
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Figure 3.1: Photographs…
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APA (6th Edition):
Broeckhoven, C. (2015). Causes and consequences of body armour in the group-living lizard, Ouroborus cataphractus (Cordylidae). (Doctoral Dissertation). Stellenbosch University. Retrieved from http://hdl.handle.net/10019.1/96602
Chicago Manual of Style (16th Edition):
Broeckhoven, Chris. “Causes and consequences of body armour in the group-living lizard, Ouroborus cataphractus (Cordylidae).” 2015. Doctoral Dissertation, Stellenbosch University. Accessed January 26, 2021.
http://hdl.handle.net/10019.1/96602.
MLA Handbook (7th Edition):
Broeckhoven, Chris. “Causes and consequences of body armour in the group-living lizard, Ouroborus cataphractus (Cordylidae).” 2015. Web. 26 Jan 2021.
Vancouver:
Broeckhoven C. Causes and consequences of body armour in the group-living lizard, Ouroborus cataphractus (Cordylidae). [Internet] [Doctoral dissertation]. Stellenbosch University; 2015. [cited 2021 Jan 26].
Available from: http://hdl.handle.net/10019.1/96602.
Council of Science Editors:
Broeckhoven C. Causes and consequences of body armour in the group-living lizard, Ouroborus cataphractus (Cordylidae). [Doctoral Dissertation]. Stellenbosch University; 2015. Available from: http://hdl.handle.net/10019.1/96602
8.
Mbongwa, Nozibusiso A.
A hidden world beneath the sand : testing phylogeographic and biogeographic patterns of Southern African sandy beach species.
Degree: MSc, Botany and Zoology, 2018, Stellenbosch University
URL: http://hdl.handle.net/10019.1/103861
► ENGLISH ABSTRACT: South Africa‟s sandy shores are listed as some of the best studied in the world, however, most of these studies have focused on…
(more)
▼ ENGLISH ABSTRACT: South Africa‟s sandy shores are listed as some of the best studied in the world, however, most of these studies have focused on documenting biodiversity and the classification of beach type and there is a distinct lack of genetic data. This has led to a poor understanding of biogeographic and phylogeographic patterns of southern African sandy beach species. Thus, in order to contribute towards plugging the phylogeography knowledge gap, the objectice of this study is to determine levels of genetic differentiation in isopods of the genera Tylos and Excirolana in the South African coast to understand their genetic diversity, connectivity and diversification processes.
Individuals (n = 214) of T. granulatus were sampled from nine locations along the west coast of South Africa and Namibia, almost covering the full distribution range of the species. Sequence data was obtained using the mitochondrial genes, COI and 16S. A total of ten sampling locations were covered for E. latipes (n = 140) and nine for E. natalensis (n = 171). For both species, sequence data was obtained with the mtDNA COI gene.
Sequences from the COI gene of T. granulatus yielded 44 haplotypes and 91% singletons. Overall, results indicated high haplotype diversity (h = 0.25 - 1.00) and low nucleotide diversity (π = 0.00 - 0.13). Further analyses revealed a strong pattern of genetic divergence characterized by two deeply divergent lineages of T. granulatus, with pairwise comparisons (Φst) ranging from 0.01 to 0.98 (P < 0.05). The genetic pattern is influenced by a phylogeographic break located between Hondeklip Bay and Kleinzee. Dating this divergence reveals a link to the Plio-Pleistocene transition that was characterized by low ocean temperatures and rapid climate and oceanographic oscillations, that also had major impacts on biogeographic and phylogeographic patterns of marine species elsewhere.
Results indicated that E. latipes and E. natalensis are sister species with monophyletic groupings. Excirolana latipes was characterized by a strong genetic structure across Cape Point, that appears to act as a barrier to gene flow between the western and southern lineages. Similarly, mtDNA COI revealed two distinct lineages within E.natalensis, although Cape Point did not appear as a significant barrier to gene flow for this species. This provides evidence that although both species have similar life-history patterns and are sympatric; their phylogeographic patterns are driven by different phylogeographic breaks. The estimates of the divergence within lineages of both Excirolana species (140 000 - 1.23 Ma) suggest a strong link with the Pleistocene period. In addition, both Excirolana species were characterised by deeply divergent lineages, potentially indicating cryptic species.
This study revealed unknown diversities and possibilities of cryptic speciation. All three isopods were characterized by distinct lineages that should be regarded at least as Management Units (MUs) until nuclear markers and further samples are added. These MUs…
Advisors/Committee Members: Von der Heyden, Sophie, Hui, Cang, Stellenbosch University. Faculty of Science. Dept. of Botany and Zoology..
Subjects/Keywords: Phylogeographic breaks; Biogeographic patterns; Sandy beach species of Southern Africa; Tylos – Genetics; Excirolana – Genetics; UCTD
…Stellenbosch University https://scholar.sun.ac.za
4.4 Population structure… …amplification …...52
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8… …viii
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21. Evidence for cryptic species or… …81
Appendix …..102
ix
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x
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Table 3.2: Haplotype…
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APA (6th Edition):
Mbongwa, N. A. (2018). A hidden world beneath the sand : testing phylogeographic and biogeographic patterns of Southern African sandy beach species. (Masters Thesis). Stellenbosch University. Retrieved from http://hdl.handle.net/10019.1/103861
Chicago Manual of Style (16th Edition):
Mbongwa, Nozibusiso A. “A hidden world beneath the sand : testing phylogeographic and biogeographic patterns of Southern African sandy beach species.” 2018. Masters Thesis, Stellenbosch University. Accessed January 26, 2021.
http://hdl.handle.net/10019.1/103861.
MLA Handbook (7th Edition):
Mbongwa, Nozibusiso A. “A hidden world beneath the sand : testing phylogeographic and biogeographic patterns of Southern African sandy beach species.” 2018. Web. 26 Jan 2021.
Vancouver:
Mbongwa NA. A hidden world beneath the sand : testing phylogeographic and biogeographic patterns of Southern African sandy beach species. [Internet] [Masters thesis]. Stellenbosch University; 2018. [cited 2021 Jan 26].
Available from: http://hdl.handle.net/10019.1/103861.
Council of Science Editors:
Mbongwa NA. A hidden world beneath the sand : testing phylogeographic and biogeographic patterns of Southern African sandy beach species. [Masters Thesis]. Stellenbosch University; 2018. Available from: http://hdl.handle.net/10019.1/103861
9.
Archer, Edward.
Androgen controlled secondary sexual characters in the male African clawed frog, Xenopus laevis, as potential biomarkers for endocrine disruptor contaminants (with special reference to fungicides) in aquatic systems.
Degree: MSc, Botany and Zoology, 2014, Stellenbosch University
URL: http://hdl.handle.net/10019.1/86508
► ENGLISH ABSTRACT: Endocrine disrupting contaminants (EDCs) coming from households, industrial parks, wastewater (sewage) treatment and agricultural areas have been shown to pollute our freshwater systems.…
(more)
▼ ENGLISH ABSTRACT: Endocrine disrupting contaminants (EDCs) coming from households, industrial parks, wastewater (sewage) treatment and agricultural areas have been shown to pollute our freshwater systems. These contaminants may disrupt early development and reproductive systems in freshwater organisms (fish, frogs and crocodile species) as well as humans. Agricultural pesticides are shown as a large
contributor to endocrine disruption activity in water catchment areas through spray drift, runoff, and/or groundwater leeching. Although South Africa is recognized as the largest consumer of agricultural pesticides in Africa, few studies have been undertaken to assess the prevalence and impact of endocrine disorders activities of pesticides in local freshwater systems. Recent studies have suggested that various agricultural pesticides, especially fungicides, might have adverse effects on the male endocrine system. There is therefore a need to test for a wider range of endocrine disrupting activities (mechanisms) in environmental waters other than conventional estrogenic (feminising) activities. Furthermore, there is a need to establish biomarkers in endemic species (bio-indicators) to show endocrine disruption in vertebrates (therefore also apply to humans). The specific objectives of the study were to: (1) describe and confirm the use of androgen-controlled breeding glands in male African clawed frogs (Xenopus laevis) as a biomarker for (anti)androgenic endocrine disruption activity (Chapter 2), (2) to investigate the premature development of breeding glands in X. laevis tadpoles (pre-metamorphic) and young froglets (post-metamorphic) (Chapter 2), (3) to investigate the disruption of male reproductive traits in adult X. laevis frogs by exposure to substances disrupting two different anti-androgenic endocrine disruption pathways (Chapter 3), (4) screen for (anti)androgenic activity of individual and binary mixtures of pesticides, which are regularly used in agricultural areas in the Western Cape Province of South Africa (Chapter 4), and (5) to test for (anti)androgenic and estrogenic endocrine disrupting activities by making use of in vitro assays as well as adult male X. laevis frogs collected from selected ponds surrounded by vineyards and fruit orchards in the
Stellenbosch Winelands. The present study confirmed that male breeding glands can serve as biomarkers for (anti)androgenic endocrine disruption and that male reproductive and secondary sexual characteristics can be disrupted through two different biochemical control pathways. The study also confirmed that the expression of androgen-regulated breeding glands can be stimulated in pre-metamorphic tadpoles and immature, post-metamorphic frogs, and can thus be used for (anti)androgenic testing. The rapid testing and predictive value of an in vitro recombinant yeast screen for androgen receptor binding inhibition of selected individual or binary mixtures of pesticides was also confirmed. However, the current study showed that the predicted in vitro (anti)androgenic…
Advisors/Committee Members: van Wyk, Johannes, Hendrik, Stellenbosch University. Faculty of Science. Dept. of Botany and Zoology..
Subjects/Keywords: Zoology; Dissertations – Zoology
…Stellenbosch University http://scholar.sun.ac.za
LIST OF ABBREVIATIONS
11-KT
11… …E2
Estradiol
E2-EQ
Estradiol Equivalent
vii
Stellenbosch University http… …Action
viii
Stellenbosch University http://scholar.sun.ac.za
mRNA
Messenger Ribonucleic… …Vinclozolin
VIN-EQ
Vinclozolin Equivalent
ix
Stellenbosch University http://scholar.sun.ac.za… …Yeast Estrogen Screen
x
Stellenbosch University http://scholar.sun.ac.za
TABLE OF CONTENTS…
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APA (6th Edition):
Archer, E. (2014). Androgen controlled secondary sexual characters in the male African clawed frog, Xenopus laevis, as potential biomarkers for endocrine disruptor contaminants (with special reference to fungicides) in aquatic systems. (Masters Thesis). Stellenbosch University. Retrieved from http://hdl.handle.net/10019.1/86508
Chicago Manual of Style (16th Edition):
Archer, Edward. “Androgen controlled secondary sexual characters in the male African clawed frog, Xenopus laevis, as potential biomarkers for endocrine disruptor contaminants (with special reference to fungicides) in aquatic systems.” 2014. Masters Thesis, Stellenbosch University. Accessed January 26, 2021.
http://hdl.handle.net/10019.1/86508.
MLA Handbook (7th Edition):
Archer, Edward. “Androgen controlled secondary sexual characters in the male African clawed frog, Xenopus laevis, as potential biomarkers for endocrine disruptor contaminants (with special reference to fungicides) in aquatic systems.” 2014. Web. 26 Jan 2021.
Vancouver:
Archer E. Androgen controlled secondary sexual characters in the male African clawed frog, Xenopus laevis, as potential biomarkers for endocrine disruptor contaminants (with special reference to fungicides) in aquatic systems. [Internet] [Masters thesis]. Stellenbosch University; 2014. [cited 2021 Jan 26].
Available from: http://hdl.handle.net/10019.1/86508.
Council of Science Editors:
Archer E. Androgen controlled secondary sexual characters in the male African clawed frog, Xenopus laevis, as potential biomarkers for endocrine disruptor contaminants (with special reference to fungicides) in aquatic systems. [Masters Thesis]. Stellenbosch University; 2014. Available from: http://hdl.handle.net/10019.1/86508
10.
Magangana, Tandokazi.
In vitro growth and development of the sweet medicinal plant Stevia rebaudiana Bertoni.
Degree: MSc, Botany and Zoology, 2017, Stellenbosch University
URL: http://hdl.handle.net/10019.1/101423
► ENGLISH ABSTRACT: Stevia rebaudiana Bertoni is a plant native to the Amambay region located north-east of Paraguay in South America. S. rebaudiana is a natural,…
(more)
▼ ENGLISH ABSTRACT: Stevia rebaudiana Bertoni is a plant native to the Amambay region located north-east of Paraguay in South America. S. rebaudiana is a natural, sweet perennial herb that contains ent-kaurene diterpene glycosides in its leaves. There are over 9 ent-kaurene diterpene glycosides and stevioside is the most abundant but rebaudioside A is the sweetest. S. rebaudiana also commonly known as Stevia is recognized to have great economic and scientific value around the world due to its sweetness and reported therapeutic properties. As a result, it is cultivated commercially in certain parts of the world. This, however, excludes southern Africa. South Africa has an opportunity to cultivate S. rebaudiana as a new crop for the agricultural sector. The aim of this study was to establish a protocol to determine the best treatment for optimal seed germination using acid scarification, smoke-water, a combination of acid scarification and smoke-water and gibberellic acid. To study the macronutritional requirements of S. rebaudiana plants utilizing nitrogen and phosphate manipulation in vitro. To determine if in vitro derived plant extracts differ in metabolite profiles regarding the main bio-actives (diterpene glycosides) using a metabolomic approach that involved the application of LC-MS and GC-MS technology. To determine the effects of drought and salinity stress on the growth of S. rebaudiana using different concentrations of (w/v) polyethylene glycol 6000 (PEG 6000) and sodium chloride (NaCl) as osmotica.
This plant exhibits a low seed germination rate which is a great challenge towards large scale propagation thus making its production expensive. Using a tissue culture system as a propagation study tool, germination of Stevia seeds was tested using 1% (w/v) 2, 3, 5-triphenyl tetrazolium chloride solution in this study. This showed a low viability of 19%. S. rebaudiana seeds were subjected to four variables namely: smoke water extract, chemical scarification using 70% (v/v) sulfuric acid for 30 seconds, a combination of smoke water extract and 70% (v/v) sulfuric acid and gibberellic acid were tested as a means of improving germination in vitro. The smoke treatment was highly efficacious in producing a significant germination percentage (P < 0.05) while seeds scarified using 70% (v/v) H2SO4 had the lowest germination rate.
To test the effect of macronutrients (nitrogen and phosphate), various levels of nitrogen and phosphate were added to the growth medium. Thereafter, liquid chromatography-mass spectrometry was used to analyze the effects on the metabolomic profile. All other 85 nutritional elements were kept similar to the control which contained similar concentrations as Murashige and Skoog (1962) medium (MS) with both nitrogen (NH4NO3 at 20.61 mM and KNO3 at 18.79 mM) and phosphate (KH2PO4 at 1.25 mM). Two distinct clusters were revealed after principal component analysis of the metabolite profiles. The orthogonal partial least squares discriminant analysis was also applied. This allowed the organization of the…
Advisors/Committee Members: Makunga, Nokwanda P., Stellenbosch University. Faculty of Science. Dept. of Botany and Zoology..
Subjects/Keywords: Medicinal plants – Breeding; Stevia rebaudiana Bertoni; Seed germination; Macronutritional requirements of Stevia rebaudiana; UCTD
…Stellenbosch University https://scholar.sun.ac.za
Dedication
I would like to dedicate… …such a blessing to me.
vii
Stellenbosch University https://scholar.sun.ac.za… …Analytical Facility (Stellenbosch University) for the GC- and LC-MS analyses.
Special… …Department
of Statistics and Actuarial Sciences (Stellenbosch University).
To the… …viii
Stellenbosch University https://scholar.sun.ac.za
Table of contents
Declaration…
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APA (6th Edition):
Magangana, T. (2017). In vitro growth and development of the sweet medicinal plant Stevia rebaudiana Bertoni. (Masters Thesis). Stellenbosch University. Retrieved from http://hdl.handle.net/10019.1/101423
Chicago Manual of Style (16th Edition):
Magangana, Tandokazi. “In vitro growth and development of the sweet medicinal plant Stevia rebaudiana Bertoni.” 2017. Masters Thesis, Stellenbosch University. Accessed January 26, 2021.
http://hdl.handle.net/10019.1/101423.
MLA Handbook (7th Edition):
Magangana, Tandokazi. “In vitro growth and development of the sweet medicinal plant Stevia rebaudiana Bertoni.” 2017. Web. 26 Jan 2021.
Vancouver:
Magangana T. In vitro growth and development of the sweet medicinal plant Stevia rebaudiana Bertoni. [Internet] [Masters thesis]. Stellenbosch University; 2017. [cited 2021 Jan 26].
Available from: http://hdl.handle.net/10019.1/101423.
Council of Science Editors:
Magangana T. In vitro growth and development of the sweet medicinal plant Stevia rebaudiana Bertoni. [Masters Thesis]. Stellenbosch University; 2017. Available from: http://hdl.handle.net/10019.1/101423
11.
Edwards, Shelley.
Patterns and processes of adaptation in Lacertid lizards to environments in southern Africa.
Degree: PhD, Botany and Zoology, 2013, Stellenbosch University
URL: http://hdl.handle.net/10019.1/85641
► ENGLISH ABSTRACT: The phenotype of an individual has often been used as the descriminating factor in distinguishing species. However, with the advent of more precise…
(more)
▼ ENGLISH ABSTRACT: The phenotype of an individual has often been used as the descriminating factor in distinguishing
species. However, with the advent of more precise molecular techniques, the genotype of species is
increasingly being used as the preferred method in taxonomic classifications. Many taxa have recently
been demonstrated to be incongruent in terms of their genetic and morphological groupings, and this
may due to the influence that the environment may have on the morphological and functional aspects of
a species. Selective pressures often act upon the performance of a species within a particular habitat
first, and then selection for the morphological characters that allow for optimal performance occurs.
Should genetically disparate species inhabit a particular environment, convergence in morphologies and
performance may evolve. Historically, lizard species descriptions were based primarily on external
morphologies, and thus misclassfication of species may have occurred due to mistakenly grouping
species with convergent morphologies together. In the current dissertation, the links between
morphology, performance capacities, diet and behaviour is explored in comparison to the environment
and genetic relationships of southern African lacertid lizards. The performance capacities and associated
morphological traits were expected to be more closely linked with the environment, and not closely
linked with genetic relationships. To investigate these expectations, a multidisciplinary approach was
taken, and genetic, morphological and performance analyses were done and compared with dietary
behavioural and environmental analyses. In the first chapter, the link between habitat openness and the
lizard bauplans is investigated and the presence of convergent morphologies within this group of lizards
is uncovered. These convergences are shown to have resulted in misclassification of two lacertid species,
and taxonomic revisions within the family are discussed. The second chapter explores the link between
performance and associated morphological traits, and the dietary composition of the members of the
Nucras genus. The third chapter identifies the link between the predator escape strategies employed by
the members of the Meroles genus, and their morphologies and performance capacities. The fourth
chapter explores the intraspecific, inter-population differences in morphologies and investigates the link
between the morphological groupings and the population genetic groupings within Pedioplanis
lineoocellata. The final chapter identifies whether adaptation to a novel habitat can occur over a
relatively short period of time, and the morphological traits, functional aspects, and population genetic
structure is investigated in conjunction with environmental analyses of vegetation and substrate between
the populations of Meroles knoxii. It was concluded that the morphological and functional aspects of the
southern African lacertid lizards are more closely related to the environment, particularly the…
Advisors/Committee Members: Tolley, Krystal, Mouton, Le Fras, Stellenbosch University. Faculty of Science. Dept. of Botany and Zoology..
Subjects/Keywords: Zoology; Dissertations – Zoology
…Stellenbosch University http://scholar.sun.ac.za
ACKNOWLEDGEMENTS
I thank the National… …Ellerman Collection (Stellenbosch University) for access
and use of their collections… …inspiration to strive for bigger and better things.
v|Page
Stellenbosch University http… …x29; views of the
crania.
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Chapter 3
vi | P a g e
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vii | P a g e
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Table
number…
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APA (6th Edition):
Edwards, S. (2013). Patterns and processes of adaptation in Lacertid lizards to environments in southern Africa. (Doctoral Dissertation). Stellenbosch University. Retrieved from http://hdl.handle.net/10019.1/85641
Chicago Manual of Style (16th Edition):
Edwards, Shelley. “Patterns and processes of adaptation in Lacertid lizards to environments in southern Africa.” 2013. Doctoral Dissertation, Stellenbosch University. Accessed January 26, 2021.
http://hdl.handle.net/10019.1/85641.
MLA Handbook (7th Edition):
Edwards, Shelley. “Patterns and processes of adaptation in Lacertid lizards to environments in southern Africa.” 2013. Web. 26 Jan 2021.
Vancouver:
Edwards S. Patterns and processes of adaptation in Lacertid lizards to environments in southern Africa. [Internet] [Doctoral dissertation]. Stellenbosch University; 2013. [cited 2021 Jan 26].
Available from: http://hdl.handle.net/10019.1/85641.
Council of Science Editors:
Edwards S. Patterns and processes of adaptation in Lacertid lizards to environments in southern Africa. [Doctoral Dissertation]. Stellenbosch University; 2013. Available from: http://hdl.handle.net/10019.1/85641
12.
Van der Colff, Dewidine.
Plant stress and the prevalence of pests and pathogens associated with a native and an invasive alien legume tree in the Cape Floristic Region, South Africa.
Degree: MSc, Botany and Zoology, 2014, Stellenbosch University
URL: http://hdl.handle.net/10019.1/86322
► ENGLISH ABSTRACT: Invasive alien plant species have devastating effects on the environments that they invade. Australian Acacias, a group of plants that has been planted…
(more)
▼ ENGLISH ABSTRACT: Invasive alien plant species have devastating effects on the environments that they invade. Australian Acacias, a group of plants that has been planted globally for a range of uses, but has escape plantation areas and became invasive in many countries, are particularly problematic. Acacia mearnsii is one of these invasive alien plant species and in South Africa it is also an important forestry species. It is currently the fifth most widespread invasive alien plant in South Africa, only restricted by the very arid Karoo, thus it is important to assess the different habitats that it enters. The Afromontane forest complex in South Africa is highly fragmented and is one of the most threatened Biomes in the country. The widespread forest margin tree Virgilia divaricata occurs within these forest margins. It is ecologically similar to A. mearnsii as these two species share many characteristics (nodulating legumes, forest pioneer species, fast growing and fire adapted). These species occur sympatrically within invaded forest margins and within these sites, there is a potential for biological exchanges of associated pests and pathogens in the form of arthropods and fungal species. We hypothesize that these two species have different interactions with their pests and pathogens in accordance with the Enemy Release Hypothesis (ERH) and the Biotic Resistance Hypothesis (BRH), respectively. We first compared arthropod associates between these two tree species and found that they share many arthropod species. The native tree did, however, have much higher abundances of herbivores and overall arthropod associates than the invasive tree species, which supports the predictions of the ERH. The distribution of these two species also had an effect on their arthropod assemblages. We assessed their ophiostomatoid fungal associates and herbivore loads and then determined how these pests and pathogens were influenced by environmental conditions along a water gradient. We also compared the effect of plant nutrient content of the two tree species on pest and pathogen loads. A. mearnsii was unaffected by water limitation along this gradient, while δ12C/ δ13C analyses showed that V. divaricata trees experienced drought within drier sites. V. divaricata also had higher herbivore loads in drier sites. A. mearnsii had higher herbivore loads on nutrient deficient trees and higher disease development in trees with sufficient nutrient levels. Comparisons of the nutrient economies of the two legume trees showed that they had similar leaf nutrient contents and resorption efficiencies, but they differed in the use of Biological Nitrogen Fixation (BNF). The native tree utilized BNF more than the invasive. We also tested the physiological effects of a native fungal species on the two tree species. We found the infection elicited more response from the invasive, while the native plant was almost non-responsive. Both plants had significantly longer lesions on infected seedlings than on control plants after inoculation with this pathogen.…
Advisors/Committee Members: Roets, F., Valentine, A., Dreyer, L. L., Stellenbosch University. Faculty of Science. Dept. of Botany and Zoology..
Subjects/Keywords: Botany; Dissertations – Botany
…Stellenbosch University http://scholar.sun.ac.za
Rhoda Malgas for moral support and… …2013.
vii
Stellenbosch University http://scholar.sun.ac.za
Dedication
I dedicate this… …have it.
viii
Stellenbosch University http://scholar.sun.ac.za
Table of Contents… …35
ix
Stellenbosch University http://scholar.sun.ac.za
3.1 Arthropod alpha-diversity… …75
x
Stellenbosch University http://scholar.sun.ac.za
4. Discussion…
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CSE |
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APA (6th Edition):
Van der Colff, D. (2014). Plant stress and the prevalence of pests and pathogens associated with a native and an invasive alien legume tree in the Cape Floristic Region, South Africa. (Masters Thesis). Stellenbosch University. Retrieved from http://hdl.handle.net/10019.1/86322
Chicago Manual of Style (16th Edition):
Van der Colff, Dewidine. “Plant stress and the prevalence of pests and pathogens associated with a native and an invasive alien legume tree in the Cape Floristic Region, South Africa.” 2014. Masters Thesis, Stellenbosch University. Accessed January 26, 2021.
http://hdl.handle.net/10019.1/86322.
MLA Handbook (7th Edition):
Van der Colff, Dewidine. “Plant stress and the prevalence of pests and pathogens associated with a native and an invasive alien legume tree in the Cape Floristic Region, South Africa.” 2014. Web. 26 Jan 2021.
Vancouver:
Van der Colff D. Plant stress and the prevalence of pests and pathogens associated with a native and an invasive alien legume tree in the Cape Floristic Region, South Africa. [Internet] [Masters thesis]. Stellenbosch University; 2014. [cited 2021 Jan 26].
Available from: http://hdl.handle.net/10019.1/86322.
Council of Science Editors:
Van der Colff D. Plant stress and the prevalence of pests and pathogens associated with a native and an invasive alien legume tree in the Cape Floristic Region, South Africa. [Masters Thesis]. Stellenbosch University; 2014. Available from: http://hdl.handle.net/10019.1/86322
13.
Ruwanza, Sheunesu.
Opportunities and contraints in the restoration of riparian ecosystems invaded by alien trees : insights from the Western Cape, South Africa.
Degree: PhD, Botany and Zoology, 2012, Stellenbosch University
URL: http://hdl.handle.net/10019.1/71755
► ENGLISH ABSTRACT: Invasive alien species are widely considered to be the second most significant threat to biodiversity globally following direct habitat destruction. The invasion of…
(more)
▼ ENGLISH ABSTRACT: Invasive alien species are widely considered to be the second most significant threat to biodiversity globally following direct habitat destruction. The invasion of riparian systems worldwide by alien plants has contributed to profound changes in biodiversity and ecosystem functioning. In South Africa, river banks and river beds are amongst the most severely invaded landscapes, with the most damaging invaders, especially in the Fynbos Biome, being trees and shrubs of the Australian genera Acacia and Eucalyptus. Although large-scale management operations are underway to clear invasive trees and restore ecosystems, little is known regarding opportunities and constraints of native species recovery after alien clearing. The core aim of this thesis is to consider whether key aspects of two widely cited restoration models (successional and alternative-state models) are useful for guiding effective management of severely-invaded riparian vegetation. As a study system, I used the Berg River in the Western Cape, South Africa which is severely impacted by invasive trees, especially Eucalyptus camaldulensis. By linking the studies of constraints for restoration and opportunities for native species recovery, the aim was to provide new possibilities for restoration in riparian zones.
The thesis starts by examining constraints to restoration following alien invasion, in particular allelopathy which is one of the factors that exacerbate the impacts of Eucalyptus invasion and inhibit recovery of natural vegetation after clearing. I further assess opportunities for both passive (based on the successional model) and active restoration (based on the alternative-state model) following different strategies for removing invasive trees. The aim is to determine the effectiveness of the different models for sustainable, goal-directed management. Finally, I investigate soil-related properties namely water repellency, soil moisture and infiltration that benefit from alien clearing and subsequent recovery of native vegetation.
Work on allelopathy as a restoration constrain showed that the presence of E. camaldulensis along the Berg River negatively affects the recovery of native species. Eucalyptus camaldulensis is allelopathic and induces soil water repellency. I recommend the removal of E. camaldulensis from riparian systems as this has the potential to restore soils to a non-allelopathic and non-repellent state that can pave way for native vegetation recovery.
Native vegetation recovery showed mixed results. Restoration based on the successional model was generally efficient, whereas restoration based on tenets of the alternative-state model was inefficient mainly due to the several constraints active restoration faced. Native species recovery was successful on both completely cleared and thinned sites that were treated four years ago. Cover of native trees and shrubs was higher in both completely cleared and thinned sites compared to invaded sites, indicating that both methods promote indigenous vegetation recovery and…
Advisors/Committee Members: Richardson, D. M., Esler, K. J., Gaertner, Mirijam, Stellenbosch University. Faculty of Science. Dept. of Botany and Zoology..
Subjects/Keywords: Botany; Dissertations – Botany
…Stellenbosch University http://scholar.sun.ac.za
Acknowledgements
I am ever grateful to… …The Oppenheimer Memorial Trust for additional funding
Stellenbosch University (… …friends for the support and encouragement
viii | P a g e
Stellenbosch University http… …19
ix | P a g e
Stellenbosch University http://scholar.sun.ac.za
2.2.3. E. camaldulensis… …49
x|Page
Stellenbosch University http://scholar.sun.ac.za
3.2.4. Data analysis…
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APA ·
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APA (6th Edition):
Ruwanza, S. (2012). Opportunities and contraints in the restoration of riparian ecosystems invaded by alien trees : insights from the Western Cape, South Africa. (Doctoral Dissertation). Stellenbosch University. Retrieved from http://hdl.handle.net/10019.1/71755
Chicago Manual of Style (16th Edition):
Ruwanza, Sheunesu. “Opportunities and contraints in the restoration of riparian ecosystems invaded by alien trees : insights from the Western Cape, South Africa.” 2012. Doctoral Dissertation, Stellenbosch University. Accessed January 26, 2021.
http://hdl.handle.net/10019.1/71755.
MLA Handbook (7th Edition):
Ruwanza, Sheunesu. “Opportunities and contraints in the restoration of riparian ecosystems invaded by alien trees : insights from the Western Cape, South Africa.” 2012. Web. 26 Jan 2021.
Vancouver:
Ruwanza S. Opportunities and contraints in the restoration of riparian ecosystems invaded by alien trees : insights from the Western Cape, South Africa. [Internet] [Doctoral dissertation]. Stellenbosch University; 2012. [cited 2021 Jan 26].
Available from: http://hdl.handle.net/10019.1/71755.
Council of Science Editors:
Ruwanza S. Opportunities and contraints in the restoration of riparian ecosystems invaded by alien trees : insights from the Western Cape, South Africa. [Doctoral Dissertation]. Stellenbosch University; 2012. Available from: http://hdl.handle.net/10019.1/71755
Stellenbosch University
14.
Phair, Nikki.
Vulnerability to future environmental conditions and population genetics of the seagrass, Zostera capensis.
Degree: MSc, Botany and Zoology, 2016, Stellenbosch University
URL: http://hdl.handle.net/10019.1/98289
► ENGLISH ABSTRACT: Climate and anthropogenic-associated environmental changes are pressuring coastal ecosystems and their services. Genetic diversity is one aspect providing resilience for species to persist…
(more)
▼ ENGLISH ABSTRACT: Climate and anthropogenic-associated environmental changes are pressuring coastal ecosystems and their services. Genetic diversity is one aspect providing resilience for species to persist through environmental perturbations and maintain functional roles in ecosystems. Seagrasses are a poorly studied yet vital component of coastal systems, serving as spawning grounds and nurseries for ecologically and commercially important species. As such, this thesis studied the distribution determinants of the seagrass, Zostera capensis, in order to assess the potential impact of environmental change on its distribution in South Africa. Further, I investigated the population genetics of Z. capensis in southern Africa.
Generalised additive modelling was applied in chapter one to quantify the relative importance of likely determinants of the contemporary distribution of Z. capensis, then to project its potential future distribution to examine its vulnerability to projected South African environmental conditions. Estuarine mouth state and precipitation were major determinants of contemporary Z. capensis distribution. My model projected the loss of significant areas (30%) of suitable habitat for Z. capensis near current range limits, placing the species at increased risk of contraction into a diminishing range of only a few estuaries on the south-eastern coast. These results align with projections of diminishing ranges for other seagrasses globally and raise concerns about future declines in extent and quality of seagrass habitat, particularly the negative effects on coastal biodiversity, commercially important fish populations with seagrass-dependant juvenile stages and trophic transfers to adjacent marine ecosystems. I recommend that marine spatial and biodiversity management planning be guided by assessing the on-going status of such species through monitoring, while also targeting seagrass protection in southerly sites to optimize future resilience.
Chapter two aimed to understand genetic diversity, gene flow and population structure of Z. capensis populations in southern African using microsatellite markers designed for a sister species, ITS and matK regions. Although many seagrasses reproduce largely vegetatively, species such as Zostera marina display high levels of clonal diversity, significant isolation by distance and strong population structure at both regional and fine scales. As Z. capensis is found across a broad range of temperature and environmental conditions, and across South African bioregions, I expected to find similar trends to those observed in Z. marina. Sequences from the matK region confirmed the species identification of all samples and showed little to no variation across all populations. ITS was excluded as multiple fragments of similar size were amplified by this marker. The nine microsatellites markers were unsuccessful at amplifying Z. capensis, and due to time and financial constraints, new microsatellite markers could not be designed. The lack of observed variation suggests a high…
Advisors/Committee Members: Von der Heyden, Sophie, Pillay, Deena, Stellenbosch University. Faculty of Science. Dept. of Botany and Zoology..
Subjects/Keywords: Zostera capensis – Population genetics – South Africa; Zostera capensis – Environmental aspects; Estuarine ecology; UCTD
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APA (6th Edition):
Phair, N. (2016). Vulnerability to future environmental conditions and population genetics of the seagrass, Zostera capensis. (Masters Thesis). Stellenbosch University. Retrieved from http://hdl.handle.net/10019.1/98289
Chicago Manual of Style (16th Edition):
Phair, Nikki. “Vulnerability to future environmental conditions and population genetics of the seagrass, Zostera capensis.” 2016. Masters Thesis, Stellenbosch University. Accessed January 26, 2021.
http://hdl.handle.net/10019.1/98289.
MLA Handbook (7th Edition):
Phair, Nikki. “Vulnerability to future environmental conditions and population genetics of the seagrass, Zostera capensis.” 2016. Web. 26 Jan 2021.
Vancouver:
Phair N. Vulnerability to future environmental conditions and population genetics of the seagrass, Zostera capensis. [Internet] [Masters thesis]. Stellenbosch University; 2016. [cited 2021 Jan 26].
Available from: http://hdl.handle.net/10019.1/98289.
Council of Science Editors:
Phair N. Vulnerability to future environmental conditions and population genetics of the seagrass, Zostera capensis. [Masters Thesis]. Stellenbosch University; 2016. Available from: http://hdl.handle.net/10019.1/98289
Stellenbosch University
15.
Haupt, Tanya Magdeleen.
Wandering albatross, Diomedea exulans, and the flightless moth, Pringleophaga marioni, on sub-Antarctic Marion Island : a case of thermal ecosystem engineering.
Degree: PhD, Botany and Zoology, 2014, Stellenbosch University
URL: http://hdl.handle.net/10019.1/86747
► ENGLISH ABSTRACT: Recent work has shown that on sub-Antarctic Marion Island, caterpillars of the flightless tineid moth, Pringleophaga marioni, have much higher and considerably less…
(more)
▼ ENGLISH ABSTRACT: Recent work has shown that on sub-Antarctic Marion Island, caterpillars of the flightless
tineid moth, Pringleophaga marioni, have much higher and considerably less variable
populations in recently abandoned nests of the wandering albatross, Diomedea exulans,
compared to old nests and other plant communities. Since no evidence for nutrient input was
provided, it was hypothesised that wandering albatrosses serve as thermal ecosystem
engineers by providing a warm microhabitat in which caterpillar growth and survival are
improved. In this thesis, I used a multidisciplinary approach integrating physiology, ecology
and behaviour, to better understand the reason for the high caterpillar biomass in nests, and
explore the hypothesis of thermal ecosystem engineering.
My first objective was to provide a more quantitative life-cycle estimate for P.
marioni by rearing caterpillars at different temperature regimes, and in so doing estimate the
effects of temperature on development and survival (Chapter 2). Contrary to previous
estimates of 2-5 years, a year-long life cycle estimate was found, and although development
was fastest at high temperatures of 15°C, caterpillars had low survival. Development time
was similar at the fluctuating temperatures of 5-15°C and 10°C, with a longer duration at
5°C.
By conducting a more extensive sampling effort of caterpillar biomass and
temperature in nests (Chapter 3), I showed that recently abandoned nests had a significantly
higher abundance of caterpillars compared to nests from which chicks had recently fledged,
as well as older nests. Temperature data collected over a c. one year period showed that
temperature in occupied nests remained high during the entire year of occupancy and events
at which P. marioni experience chill coma were substantially reduced.
Consequently, the effects of thermal acclimation on the physiological and behavioural
responses of P. marioni caterpillars were explored. First, how temperature affects the
metabolic rate of caterpillars was examined (Chapter 4). Metabolic rate was significantly
higher at a low acclimation temperature of 5°C compared to 15°C, providing partial support
for metabolic cold adaptation. No evidence was provided that caterpillars reduce their
metabolic rates to conserve water, and caterpillars responded to fluctuating temperatures by
depressing their metabolic rates. Second, the relationship between thermal preference and
locomotor performance of caterpillars was examined (Chapter 5). A common assumption
made is that animals will prefer temperatures that maximise performance. Preference was
significantly lower (c. 8°C) compared to the optimum temperature for locomotion (c. 23°C),
and it was suggested that caterpillars may prefer lower temperatures where survival or assimilation efficiency is maximised. Lastly, if nests provide a fitness advantage, either
caterpillars or ovipositing female moths may likely seek out nests. Using choice experiments
(Chapter 6), I showed that caterpillars are…
Advisors/Committee Members: Chown, Steven L., Sinclair, Brent J., Stellenbosch University. Faculty of Science. Dept. of Botany and Zoology..
Subjects/Keywords: Sub-Antarctic caterpillars; Wandering Albatross (Diomedea exulans) – Marion Island; Flightless moth (Pringleophaga marioni) – Marion Island; Thermal ecosystem engineering; UCTD
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APA ·
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APA (6th Edition):
Haupt, T. M. (2014). Wandering albatross, Diomedea exulans, and the flightless moth, Pringleophaga marioni, on sub-Antarctic Marion Island : a case of thermal ecosystem engineering. (Doctoral Dissertation). Stellenbosch University. Retrieved from http://hdl.handle.net/10019.1/86747
Chicago Manual of Style (16th Edition):
Haupt, Tanya Magdeleen. “Wandering albatross, Diomedea exulans, and the flightless moth, Pringleophaga marioni, on sub-Antarctic Marion Island : a case of thermal ecosystem engineering.” 2014. Doctoral Dissertation, Stellenbosch University. Accessed January 26, 2021.
http://hdl.handle.net/10019.1/86747.
MLA Handbook (7th Edition):
Haupt, Tanya Magdeleen. “Wandering albatross, Diomedea exulans, and the flightless moth, Pringleophaga marioni, on sub-Antarctic Marion Island : a case of thermal ecosystem engineering.” 2014. Web. 26 Jan 2021.
Vancouver:
Haupt TM. Wandering albatross, Diomedea exulans, and the flightless moth, Pringleophaga marioni, on sub-Antarctic Marion Island : a case of thermal ecosystem engineering. [Internet] [Doctoral dissertation]. Stellenbosch University; 2014. [cited 2021 Jan 26].
Available from: http://hdl.handle.net/10019.1/86747.
Council of Science Editors:
Haupt TM. Wandering albatross, Diomedea exulans, and the flightless moth, Pringleophaga marioni, on sub-Antarctic Marion Island : a case of thermal ecosystem engineering. [Doctoral Dissertation]. Stellenbosch University; 2014. Available from: http://hdl.handle.net/10019.1/86747
Stellenbosch University
16.
Rogers, Andrew M. (Andrew Munro).
Avian assemblages of invasive Australian Acacia thickets in the Western Cape.
Degree: MSc, Botany and Zoology, 2012, Stellenbosch University
URL: http://hdl.handle.net/10019.1/20303
► ENGLISH ABSTRACT: Human-modified habitats form increasingly large components of landscapes, threatening biodiversity and creating challenges for conservation. In some cases altered habitats form entirely novel…
(more)
▼ ENGLISH ABSTRACT: Human-modified habitats form increasingly large components of landscapes, threatening
biodiversity and creating challenges for conservation. In some cases altered habitats form
entirely novel ecosystems that may support new combinations of species and species
abundances, and create habitat space in otherwise transformed landscapes. In the Western
Cape of South Africa, woody invasive species contribute to landscape-level habitat
transformation and form novel ecosystems. Invasive Australian Acacia species are especially
problematic in lowland areas where they create dense thickets and substantially transform
both biotic communities and abiotic processes. Despite the prominence of Acacia thickets
across the Western Cape, their ability to support native fauna is not well understood and the
objective of this study was to assess the significance of Acacia thickets as habitat for the
region’s avifauna. Birds were surveyed in Acacia thickets in the south-western Western Cape
in three seasons to examine species richness, abundance and functional abundance.
Furthermore, I examined the extent to which differences in patch-level vegetation structure
alter bird communities. Between survey sites and seasons, significant variation was observed
in assemblage richness, density, median body size and biomass. Variation in vegetation
density, stem density, mean vegetation height and total canopy cover best explained variation
in bird assemblages. Eighty species were estimated to utilize Acacia thickets and assemblages
had a mean density of 7.78 birds per ha. The most abundant feeding guilds were the mixed
feeders and insectivores. The median body size observed was 15.2 g and the body size
frequency distribution of all species in Acacia spanned a similar range compared to the body
size frequency distribution for the species list for the entire Western Cape. The mean biomass
of bird communities was 0.224 kg per ha. Using data on bird density and biomass, Acacia
thickets across the Fynbos Biome support and estimated average of over 21 million birds with
a combined biomass of over 600 thousand kg. This study found that Acacia thickets in the
Western Cape support a subset of the region’s birds with the most abundant species being
small mixed feeders, which are also frequently urban-adapted. Compared with other habitat
types, Acacia support bird assemblages with moderate species richness and density. This
study shows that Acacia thickets, as a novel habitat, provide a significant amount of habitat
space in a highly transformed landscape and highlights the need for comprehensive evaluation of altered habitats before assumptions are made about their ecological value.
AFRIKAANSE OPSOMMING: Getransformeerde habitatte maak vermeerderend groot deel uit van die omgewing, dit bedreig
biodiversiteit en skep groter uitdagings vir bewaring. In sommige gevalle vorm hierdie
getransformeerde habitatte geheel nuwe ekosisteme wat moontlik nuwe kombinasies van
spesies en spesie volopheid kan onderhou. Verder…
Advisors/Committee Members: Chown, Steven L., Stellenbosch University. Faculty of Science. Dept. of Botany and Zoology..
Subjects/Keywords: Zoology; Birds – South Africa – Western Cape; Acacia – Ecology; Novel ecosystems; Invasive species
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APA (6th Edition):
Rogers, A. M. (. M. (2012). Avian assemblages of invasive Australian Acacia thickets in the Western Cape. (Masters Thesis). Stellenbosch University. Retrieved from http://hdl.handle.net/10019.1/20303
Chicago Manual of Style (16th Edition):
Rogers, Andrew M (Andrew Munro). “Avian assemblages of invasive Australian Acacia thickets in the Western Cape.” 2012. Masters Thesis, Stellenbosch University. Accessed January 26, 2021.
http://hdl.handle.net/10019.1/20303.
MLA Handbook (7th Edition):
Rogers, Andrew M (Andrew Munro). “Avian assemblages of invasive Australian Acacia thickets in the Western Cape.” 2012. Web. 26 Jan 2021.
Vancouver:
Rogers AM(M. Avian assemblages of invasive Australian Acacia thickets in the Western Cape. [Internet] [Masters thesis]. Stellenbosch University; 2012. [cited 2021 Jan 26].
Available from: http://hdl.handle.net/10019.1/20303.
Council of Science Editors:
Rogers AM(M. Avian assemblages of invasive Australian Acacia thickets in the Western Cape. [Masters Thesis]. Stellenbosch University; 2012. Available from: http://hdl.handle.net/10019.1/20303
Stellenbosch University
17.
Janse van Rensburg, Marinel.
Reconstructing the range expansion of the European starling in Southern Africa using a hybrid method of niche modelling and individual based modelling.
Degree: MSc, Botany and Zoology, 2014, Stellenbosch University
URL: http://hdl.handle.net/10019.1/86739
► ENGLISH ABSTRACT: Much emphasis has been placed on modelling species distributions and less so on the distributional dynamics. It is important to not only ask…
(more)
▼ ENGLISH ABSTRACT: Much emphasis has been placed on modelling species distributions and less so on the distributional
dynamics. It is important to not only ask where species occur, but why and how they reached a specific
location. Biological invasions provide an ideal natural experiment for studying the drivers and dynamics of
spreading. Here, I examine the drivers and dynamics of the spread of the European Starling, Sturnus
vulgaris, in Southern Africa. Since its introduction in Cape Town in 1897, this top invasive avian species
has rapidly spread across a large extent of South Africa and is continuously expanding its current range. It
is, thus, of great theoretical and management value to elucidate the invasion process and identify key
environmental drivers of its range dynamics.
The aim of this research is twofold. First, I aim to develop realistic suitable habitat maps for the European
Starling in Southern Africa based on multiple climatic and geographic variables using two robust methods
of species distribution modelling (SDM), namely maximum entropy (MaxEnt) and boosted regression trees
(BRT). Second, I aim to, subsequently, develop a hybrid model that runs a dynamic individual-based
model (IBM) on these suitability maps predicted from the SDM. This hybrid model provides an excellent
opportunity to incorporate a variety of response regimes on how behavioural strategies and dispersal
scenarios respond to environmental and geographic features, and as a result leads to a well-rounded study
of the species‟ distribution dynamics in the region. Independent atlas data and field collections were used
to parameterize and later validate the model. This allowed me to further identify an optimal model through
a parameter sensitivity analysis sorting of the contribution of each environmental and behavioural features
to shaping the past and current geographical range of European Starling.
According to the optimal model, starlings can choose among five sites to locate the one with the highest
habitat suitability. They tend to avoid moving through areas with a 300 m elevation barrier, and the
dispersal distance per year is limited to below 200 km. At the regional scale, the starlings were able to
manoeuvre around mountainous regions and avoided the semi-desert regions of the Karoo. Their
distribution was mainly driven by high winter precipitation along the low-lying coastal regions. Future
projections of their distribution suggested a continuous range expansion throughout the provinces of the
Free State, Gauteng, North West (reaching Mahikeng, the capital of North West, in 2022) and Limpopo
(reaching Polokwane, the capital of Limpopo, in 2046) as well as into the neighbouring countries of
Mozambique and Zimbabwe (reaching Bulawayo, 2nd largest city in Zimbabwe, in 2062).
AFRIKAANSE OPSOMMING: Klem word dikwels meer geplaas op die modellering van spesies se verspreiding en minder op die
dinamika agter die verspreiding. Dit is belangrik om nie slegs te vra waar spesies voorkom nie, maar
hoekom en…
Advisors/Committee Members: Hui, Cang, Stellenbosch University. Faculty of Science. Dept. of Botany and Zoology..
Subjects/Keywords: Biogeography; Biological invations – Mathematical models; European Starling – Geographical distribution – Southern Africa; Sturnus vulgaris – Dispersal behavior; Biological invasions – Environmental aspects; European starling – Dispersal behavior; UCTD; Botany and Zoology
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APA (6th Edition):
Janse van Rensburg, M. (2014). Reconstructing the range expansion of the European starling in Southern Africa using a hybrid method of niche modelling and individual based modelling. (Masters Thesis). Stellenbosch University. Retrieved from http://hdl.handle.net/10019.1/86739
Chicago Manual of Style (16th Edition):
Janse van Rensburg, Marinel. “Reconstructing the range expansion of the European starling in Southern Africa using a hybrid method of niche modelling and individual based modelling.” 2014. Masters Thesis, Stellenbosch University. Accessed January 26, 2021.
http://hdl.handle.net/10019.1/86739.
MLA Handbook (7th Edition):
Janse van Rensburg, Marinel. “Reconstructing the range expansion of the European starling in Southern Africa using a hybrid method of niche modelling and individual based modelling.” 2014. Web. 26 Jan 2021.
Vancouver:
Janse van Rensburg M. Reconstructing the range expansion of the European starling in Southern Africa using a hybrid method of niche modelling and individual based modelling. [Internet] [Masters thesis]. Stellenbosch University; 2014. [cited 2021 Jan 26].
Available from: http://hdl.handle.net/10019.1/86739.
Council of Science Editors:
Janse van Rensburg M. Reconstructing the range expansion of the European starling in Southern Africa using a hybrid method of niche modelling and individual based modelling. [Masters Thesis]. Stellenbosch University; 2014. Available from: http://hdl.handle.net/10019.1/86739
Stellenbosch University
18.
Rossouw, Marius Wilhelmus.
Spatial variation in plant nutrient composition on Marion Island.
Degree: MSc, Botany and Zoology, 2014, Stellenbosch University
URL: http://hdl.handle.net/10019.1/86405
► ENGLISH ABSTRACT: To estimate nutrient budgets and model nutrient cycling at a whole ecosystem level on sub-Antarctic Marion Island requires information on the spatial variability…
(more)
▼ ENGLISH ABSTRACT: To estimate nutrient budgets and model nutrient cycling at a whole ecosystem level on sub-Antarctic Marion Island requires information on the spatial variability of plant nutrient concentrations on the island. The complexity of constructing budgets and models will also be reduced if, instead of considering each plant species individually, the species can be grouped on the basis of their similarities/differences in nutrient concentrations. This thesis presents the results of an investigation into both these aspects.
Altitude and distance from the sea are highly correlated with each other and thus influence the concentrations of all the nutrients considered (N, P, K, Ca, Mg and Na) very similarly. Concentrations of N, P and Na in living leaves, dead leaves, stems and roots decrease going inland, due to a decline in the influence of animal manuring and of sea spray. Ca concentration increases going inland, away from the organic peats characteristic of the lowland regions toward the mineral rawmark inland soils. Declining sea spray and increasing soil minerality going inland both affect plant Mg concentration; the net effect is a slight decrease in Mg concentration going away from the coast. K concentration in living leaves and roots did not change going inland; dead leaf and stem K concentrations showed a weak decline. Bryophyte shoot nutrient concentrations do not show such marked patterns of change going inland. Considering the bryophyte species as a whole, the only significant effect is that shoot Na concentration decreases, and Ca concentration increases, going inland. Although information on nutrient concentrations in all plant organs from all four (N, E, W and S) sides of the island was available for only a few species, and in many instances the between-side effect was not significant for individual species, the pattern of between-side differences is quite clear. Living leaf N, P and Mg concentrations are higher in west side than east side plants, with south and north side plants having intermediate concentrations. Leaf K concentrations are highest on the north and lowest on the west side, with east and south side concentrations being intermediate. Leaf Ca concentrations are highest on the south side and lowest on the north side, with east and west side Ca concentrations being intermediate. Leaf Na concentration declines more sharply with distance inland on the island's western and southern sides than on its eastern and northern sides, so that closer than 450 m from the shore leaf Na concentration is higher on the west and south than on the east or north sides, but further inland than that the difference lessens. There was sufficient information for dead leaf, stem and root nutrient concentrations only for the west and east sides of the island. West-east differences in nutrient concentrations of dead leaves are the same as for living leaves. Stem and root west-east concentration differences are also similar to those for living leaves, except for P and Mg concentrations, which were similar on…
Advisors/Committee Members: Smith, Valdon R., Stellenbosch University. Faculty of Science. Dept. of Botany and Zoology..
Subjects/Keywords: Botany; Dissertations – Botany
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APA (6th Edition):
Rossouw, M. W. (2014). Spatial variation in plant nutrient composition on Marion Island. (Masters Thesis). Stellenbosch University. Retrieved from http://hdl.handle.net/10019.1/86405
Chicago Manual of Style (16th Edition):
Rossouw, Marius Wilhelmus. “Spatial variation in plant nutrient composition on Marion Island.” 2014. Masters Thesis, Stellenbosch University. Accessed January 26, 2021.
http://hdl.handle.net/10019.1/86405.
MLA Handbook (7th Edition):
Rossouw, Marius Wilhelmus. “Spatial variation in plant nutrient composition on Marion Island.” 2014. Web. 26 Jan 2021.
Vancouver:
Rossouw MW. Spatial variation in plant nutrient composition on Marion Island. [Internet] [Masters thesis]. Stellenbosch University; 2014. [cited 2021 Jan 26].
Available from: http://hdl.handle.net/10019.1/86405.
Council of Science Editors:
Rossouw MW. Spatial variation in plant nutrient composition on Marion Island. [Masters Thesis]. Stellenbosch University; 2014. Available from: http://hdl.handle.net/10019.1/86405
Stellenbosch University
19.
Groenewald, Lida-Mari.
The development of phosphate stress and its functional consequences in the model legume plant Medicago truncatula.
Degree: MSc, Botany and Zoology, 2016, Stellenbosch University
URL: http://hdl.handle.net/10019.1/100019
► ENGLISH ABSTRACT: Phosphate is an abundant nutrient in the soil; however it is mostly bound to other elements that make phosphate unavailable for plant uptake.…
(more)
▼ ENGLISH ABSTRACT: Phosphate is an abundant nutrient in the soil; however it is mostly bound to other
elements that make phosphate unavailable for plant uptake. This bound state makes
phosphate the second most limiting nutrient for plant growth. Phosphate is also a nonrenewable
mined resource that forms a major constituent of fertiliser given to crops grown
in nutrient poor soils. The second most important crop family in agriculture is
Leguminosae. In an attempt to to reduse possible nitrogen stress, legumes can form a
symbiosis with nitrogen-fixing soil bacteria. This symbiosis, found in the nodules,
exchanges fixed nitrogen with host photosynthate and phosphate. The nodules are thus a
phosphate sink that place stress on the rest of the plant. Legumes have adapted different
ways to optimise the limited available phosphate to continue their own growth while
maintaining the adenosine-triphosphate expensive nitrogen-fixing reaction.
In this study, we looked at how the genetic model legume, Medicago truncatula
Gaertner, has adapted to phosphate stressed conditions as it relied solely on biological
nitrogen fixation as a source of nitrogen.
In the first treatment, Medicago truncatula seedlings were infected with
Sinorhizobium meliloti and received a low concentration of phosphate throughout the
growth period. This was done to simulate Medicago truncatula growing in already
phosphate deprived soils. The comparisons of biomass and growth, internal free
phosphate concentrations, and organic acid and acid phosphatases enzyme activities
were done on the above versus below ground tissues. Photosynthesis parameters were
also recorded. Above ground tissues responded to phosphate stress with increased
activity of bypass enzymes at the steps that required adenosine-triphosphate. While the
below ground tissues focused on using acid phosphatases to recycle phosphate. Although
the rate of photosynthesis had decreased in the phosphate stressed plants, the efficiency
of photosynthesis with the phosphate that was available in the leaves had increased.
The second treatment involved the growth of nodulated Medicago truncatula with an
optimal phosphate concentration, followed by an induced phosphate stress period. In this
manner, soil that had been depleted of phosphate during plant growth was simulated. With the addition of determining differences in activities of nitrogen assimilating enzymes, the
above-mentioned comparisons were made on the nodules and roots of the sample plants.
Under the induced stress condition, available phosphate was concentrated to the nodules.
A possible cause for this was the increase in activity of the organic acid synthesising
enzymes present in the nodule. The nitrogen assimilating enzyme activities indicated that
stressed nodules may export glutamine rather than asparagine to the roots. Root nitrogen
assimilating enzyme activities remained relatively constant during phosphate stress.
Reduced nitrogen and carbon content of stressed plants indicated that phosphate had a
direct…
Advisors/Committee Members: Valentine, Alexander J., Kleinert, Aleysia, Stellenbosch University. Faculty of Science. Dept. of Botany and Zoology..
Subjects/Keywords: Medicago truncatula; Phosphate stress; Plants – Assimilation; Plants – Nutrition; UCTD
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APA ·
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APA (6th Edition):
Groenewald, L. (2016). The development of phosphate stress and its functional consequences in the model legume plant Medicago truncatula. (Masters Thesis). Stellenbosch University. Retrieved from http://hdl.handle.net/10019.1/100019
Chicago Manual of Style (16th Edition):
Groenewald, Lida-Mari. “The development of phosphate stress and its functional consequences in the model legume plant Medicago truncatula.” 2016. Masters Thesis, Stellenbosch University. Accessed January 26, 2021.
http://hdl.handle.net/10019.1/100019.
MLA Handbook (7th Edition):
Groenewald, Lida-Mari. “The development of phosphate stress and its functional consequences in the model legume plant Medicago truncatula.” 2016. Web. 26 Jan 2021.
Vancouver:
Groenewald L. The development of phosphate stress and its functional consequences in the model legume plant Medicago truncatula. [Internet] [Masters thesis]. Stellenbosch University; 2016. [cited 2021 Jan 26].
Available from: http://hdl.handle.net/10019.1/100019.
Council of Science Editors:
Groenewald L. The development of phosphate stress and its functional consequences in the model legume plant Medicago truncatula. [Masters Thesis]. Stellenbosch University; 2016. Available from: http://hdl.handle.net/10019.1/100019
Stellenbosch University
20.
Davis-Reddy, Claire.
Assessing vegetation dynamics in response to climate variability and change across sub-Saharan Africa.
Degree: PhD, Botany and Zoology, 2018, Stellenbosch University
URL: http://hdl.handle.net/10019.1/103595
► ENGLISH ABSTRACT: Understanding and predicting how anthropogenic climate change is likely to impact terrestrial ecosystems across sub-Saharan Africa is a key question for both ecology…
(more)
▼ ENGLISH ABSTRACT: Understanding and predicting how anthropogenic climate change is likely to impact terrestrial ecosystems across sub-Saharan Africa is a key question for both ecology and for regional and global climate policy development. This predictive understanding hinges on a far better ability to detect, interpret, and attribute changes in vegetation cover and productivity, which is the basis for ecosystem response and resilience to anthropogenic climate change.
Monitoring and modelling of vegetation dynamics in the context of climate change requires long-term datasets of key ecosystem indicators such as vegetation productivity and phenology. The use of remotely sensed vegetation indices to detect vegetation change related to climate has become an important application of remotely sensed imagery. The third generation Normalized Difference Vegetation Index (NDVI3g) time series from the Global Inventory Modeling and Mapping Studies (GIMMS) has a 34-year long history (1982-2015) and provides unprecedented opportunity to examine vegetation dynamics in response to changes in temperature, rainfall, and increases in atmospheric carbon dioxide (CO2).
This thesis makes use of the NDVI3g time-series to examine the influence of climate on vegetation productivity and phenology in order to (i) assess recent shifts in vegetation across sub-Saharan Africa (SSA) and (ii) facilitate improved simulations of vegetation by Dynamic Global Vegetation Models (DGVMs). The NDVI3g information was integrated with climate data and large-scale climate fluctuations and oscillations in sea surface temperature and atmospheric pressure to test hypotheses on the role of both climate variability and change on vegetation activity. Seasonal and long-term patterns of change were compared with projections of a dynamic global vegetation model, the "adaptive Dynamic Global Vegetation Model" (aDGVM) that was initially developed for application in sub-Saharan Africa.
In the first component of the thesis results show that the vegetation of SSA is driven by rainfall and associated fluctuations and oscillations in sea surface temperature (SST) and atmospheric pressure, with the El Niño-Southern Oscillation (ENSO) being the most dominant driver of variability in both vegetation productivity and phenology over eastern and southern Africa. Vegetation tends to show a stronger positive response to rainfall in the 3 months preceding vegetation growth suggesting that time-lag effects are significant when assessing the influence of climate.
In the second component, trend analyses provide evidence for a number of important spatial and temporal patterns of change in vegetation productivity and phenology over SSA, which are generally consistent with independently reported long-term trends. Significant added value was provided to previous studies through the use of productivity and phenology metrics, which facilitated an assessment of vegetation dynamics at both the seasonal and inter-annual scale.
A clear latitudinal pattern of change was detected where…
Advisors/Committee Members: Midgley, Guy, Stellenbosch University. Faculty of Science. Dept. of Botany and Zoology..
Subjects/Keywords: Vegetation dynamics – Africa; Climatic changes; Africa, Sub-Saharan – Environmental aspects; UCTD
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APA (6th Edition):
Davis-Reddy, C. (2018). Assessing vegetation dynamics in response to climate variability and change across sub-Saharan Africa. (Doctoral Dissertation). Stellenbosch University. Retrieved from http://hdl.handle.net/10019.1/103595
Chicago Manual of Style (16th Edition):
Davis-Reddy, Claire. “Assessing vegetation dynamics in response to climate variability and change across sub-Saharan Africa.” 2018. Doctoral Dissertation, Stellenbosch University. Accessed January 26, 2021.
http://hdl.handle.net/10019.1/103595.
MLA Handbook (7th Edition):
Davis-Reddy, Claire. “Assessing vegetation dynamics in response to climate variability and change across sub-Saharan Africa.” 2018. Web. 26 Jan 2021.
Vancouver:
Davis-Reddy C. Assessing vegetation dynamics in response to climate variability and change across sub-Saharan Africa. [Internet] [Doctoral dissertation]. Stellenbosch University; 2018. [cited 2021 Jan 26].
Available from: http://hdl.handle.net/10019.1/103595.
Council of Science Editors:
Davis-Reddy C. Assessing vegetation dynamics in response to climate variability and change across sub-Saharan Africa. [Doctoral Dissertation]. Stellenbosch University; 2018. Available from: http://hdl.handle.net/10019.1/103595
Stellenbosch University
21.
Tonkie, Jacqueline Nicole.
Marion Island bryophytes: evidence for functional types based on traits related to photosynthesis and desiccation tolerance.
Degree: MSc, Botany and Zoology, 2016, Stellenbosch University
URL: http://hdl.handle.net/10019.1/98851
► ENGLISH ABSTRACT: There is currently a worldwide interest in grouping species on the basis of their functional characteristics into plant functional types (PFTs). This reduces…
(more)
▼ ENGLISH ABSTRACT: There is currently a worldwide interest in grouping species on the basis of their functional characteristics into plant functional types (PFTs). This reduces the complexity of models that predict the effects of global change on vegetation and ecosystem processes. Marion Island has vegetation dominated by bryophytes and is experiencing intense climate change. However, there is no accepted scheme and no consensus on the most useful traits for a bryophyte PFT classification. This study aimed at grouping 38 of the island bryophyte species into functional groups. A suite of 14 photosynthetic traits related to light or desiccation response were obtained from chlorophyll fluorescence quenching analysis and water relations. The characteristics were subjected to analysis of variance, box plot rankings, principal component and clustering analyses to group the species into functional types. Seven light response groups and nine desiccation response groups were recognized. Six groups were recognized in the combined analysis of light and desiccation traits. The species with the highest photosynthetic capacity and lowest photoinhibition had low or moderate saturated moisture content, dried out slowly, low or moderate photoprotection capability in high light and when desiccated and moderate recovery of photochemistry upon rehydration. The species with the lowest photosynthetic capacity and highest photoinhibition had the highest saturated moisture content, dried out very fast, had low photoprotective capability in high light and when desiccated and showed very low to moderate recovery. The group of species with low photosynthetic capacity was distinguished from the group with the lowest photosynthetic capacity by having a higher quantum yield of electron transport at the optimal photosynthetically active radiation (PAR). The two groups consisting of moderate or high photosynthetic capacity species were distinguished by the fraction of open reaction centres in high light and the ability to recover photochemistry upon rehydration. The group consisting of species with moderate photosynthetic capacity had a moderate fraction of open reaction centres in high light, moderate photoprotective capability when desiccated and high recovery of photochemistry upon rehydration. Correspondence analysis shows that the groupings are related to phylogeny, especially at the phylum level, and the species belonging to the same genus mostly had similar light and desiccation response characteristics. There is a strong correspondence between functional groupings, light regime and habitat moisture. The light response traits, particularly photoinhibition, are strongly associated with light regime. Photosynthetic capacity, moisture content and ability to recover photochemistry upon rehydration, correspond to habitat moisture. Life form was also strongly associated with functional groupings, particularly with the desiccation response traits.
AFRIKAANSE OPSOMMING: Daar is tans 'n wêreldwye belangstelling in die groepering van spesies in…
Advisors/Committee Members: Smith, Valdon R., Stellenbosch University. Faculty of Science. Dept. of Botany and Zoology..
Subjects/Keywords: Marion Island – Plant functional types; Marion Island vegetation; Marion Island bryophyte species; UCTD
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APA (6th Edition):
Tonkie, J. N. (2016). Marion Island bryophytes: evidence for functional types based on traits related to photosynthesis and desiccation tolerance. (Masters Thesis). Stellenbosch University. Retrieved from http://hdl.handle.net/10019.1/98851
Chicago Manual of Style (16th Edition):
Tonkie, Jacqueline Nicole. “Marion Island bryophytes: evidence for functional types based on traits related to photosynthesis and desiccation tolerance.” 2016. Masters Thesis, Stellenbosch University. Accessed January 26, 2021.
http://hdl.handle.net/10019.1/98851.
MLA Handbook (7th Edition):
Tonkie, Jacqueline Nicole. “Marion Island bryophytes: evidence for functional types based on traits related to photosynthesis and desiccation tolerance.” 2016. Web. 26 Jan 2021.
Vancouver:
Tonkie JN. Marion Island bryophytes: evidence for functional types based on traits related to photosynthesis and desiccation tolerance. [Internet] [Masters thesis]. Stellenbosch University; 2016. [cited 2021 Jan 26].
Available from: http://hdl.handle.net/10019.1/98851.
Council of Science Editors:
Tonkie JN. Marion Island bryophytes: evidence for functional types based on traits related to photosynthesis and desiccation tolerance. [Masters Thesis]. Stellenbosch University; 2016. Available from: http://hdl.handle.net/10019.1/98851
Stellenbosch University
22.
Zietsman, Alta.
Response of different plant functional types to environmental variability on Marion Island : quantifying diurnal patterns over a seasonal cycle using the photochemical reflectance index.
Degree: MSc, Botany and Zoology, 2018, Stellenbosch University
URL: http://hdl.handle.net/10019.1/103617
► ENGLISH ABSTRACT: Marion Island forms part of the Prince Edward Island group, situated near the latitude of 47° South. Seasonal and temporal variability in climate…
(more)
▼ ENGLISH ABSTRACT: Marion Island forms part of the Prince Edward Island group, situated near the latitude of 47° South. Seasonal and temporal variability in climate on Marion Island has been described as muted, due to the thermal buffering of the surrounding ocean. This is thought in turn to lead to an extended growing season. However, empirical in situ measurements of net primary production (NPP), are lower than estimations based on annual temperature and precipitation.
The aim of this study was to explore which potentially limiting environmental factors exert control over photosynthetic behaviour at a range of sub-annual temporal scales, in order to better understand what limits production in plant functional types (PFTs) typical of Marion Island. The three main PFTs selected for study were lower plants, cushion plants and grasses.
Spectral reflectance sensors were used in situ to investigate the diurnal and seasonal patterns of physiological stress and inferred photosynthetic behaviour. The Photochemical Reflectance Index (PRI) is calculated from a ratio of reflected versus incoming light wavebands, that are influenced by a change in carotenoid ratios, indicating photosynthetic efficacy through the activity of the xanthophyll cycle. The xanthophyll cycle is closely linked to photosystem II and thus an important component of the non-photochemical quenching (NPQ) process that acts as a photo-protection mechanism.
PRI measurements require careful interpretation in the absence of any independent confirmatory measurements. Repeated ancillary measurements of leaf chlorophyll fluorescence and leaf chlorophyll content via independent instrumentation provided support for the PRI measurements as an indicator of physiological stress. This approach was also used to confirm that the point monitoring of individual canopies was representative of surrounding vegetation.
Contrary to the assumption that climate variability is muted, fine temporal scale monitoring revealed remarkably high temporal climate variability on Marion Island. Although seasons sensu stricto could not be clearly defined, a shift in climate can be seen between “winter” and “summer” months, most notably by a replacement of cold, calm days by warm, windy days. PRI data revealed that different PFTs (and to an extent, individual species) showed somewhat distinct optimum growing seasons, with the seasonal shift in climate affecting PFTs differently.
The three main PFTs showed distinct PRI patterns. Lower plants showed the deepest daily PRI depression, almost regardless of environmental conditions, confirming for thefirst time over an entire annual cycle their previously proposed low light adaptive characteristics. Cushion plants only showed a midday PRI depression on days withhigh temperatures, revealing their optimal adaptation to cooler diurnal conditions. Grasses had the highest PRI values, responding positively on days with higher temperatures, and revealing their more efficient performance under warmer and brighter conditions, in distinct contrast to the…
Advisors/Committee Members: Midgley, Guy, Stellenbosch University. Faculty of Science. Dept. of Botany and Zoology..
Subjects/Keywords: Plant functional types – Prince Edward Islands – Marion Island; Photochemical Reflectance Index (PRI); Climate – Prince Edward Islands – Marion Island; Marion Island (Prince Edward Islands) – Environmental conditions; UCTD
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APA ·
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APA (6th Edition):
Zietsman, A. (2018). Response of different plant functional types to environmental variability on Marion Island : quantifying diurnal patterns over a seasonal cycle using the photochemical reflectance index. (Masters Thesis). Stellenbosch University. Retrieved from http://hdl.handle.net/10019.1/103617
Chicago Manual of Style (16th Edition):
Zietsman, Alta. “Response of different plant functional types to environmental variability on Marion Island : quantifying diurnal patterns over a seasonal cycle using the photochemical reflectance index.” 2018. Masters Thesis, Stellenbosch University. Accessed January 26, 2021.
http://hdl.handle.net/10019.1/103617.
MLA Handbook (7th Edition):
Zietsman, Alta. “Response of different plant functional types to environmental variability on Marion Island : quantifying diurnal patterns over a seasonal cycle using the photochemical reflectance index.” 2018. Web. 26 Jan 2021.
Vancouver:
Zietsman A. Response of different plant functional types to environmental variability on Marion Island : quantifying diurnal patterns over a seasonal cycle using the photochemical reflectance index. [Internet] [Masters thesis]. Stellenbosch University; 2018. [cited 2021 Jan 26].
Available from: http://hdl.handle.net/10019.1/103617.
Council of Science Editors:
Zietsman A. Response of different plant functional types to environmental variability on Marion Island : quantifying diurnal patterns over a seasonal cycle using the photochemical reflectance index. [Masters Thesis]. Stellenbosch University; 2018. Available from: http://hdl.handle.net/10019.1/103617
Stellenbosch University
23.
Louw, Anche.
Plant functional types on Marion Island.
Degree: MSc, Botany and Zoology, 2016, Stellenbosch University
URL: http://hdl.handle.net/10019.1/98483
► ENGLISH ABSTRACT: A database was compiled of structural and physiological traits for 25 vascular species and 17 bryophyte species on Marion Island (sub-Antarctic). The structural…
(more)
▼ ENGLISH ABSTRACT: A database was compiled of structural and physiological traits for 25 vascular species and 17 bryophyte species on Marion Island (sub-Antarctic). The structural traits included leaf, stem and root characteristics and the physiological traits are all associated with photosynthetic responses to light and were measured using chlorophyll fluorescence quenching analysis. The data were subjected to principal component analysis and clustering analysis to construct a suite of plant functional types (PFTs). The correspondences between the PFTs and plant habit/taxonomy (forb, graminoid, fern, moss and liverwort), status (native to the island or introduced alien) and habitat (oligotrophic, manured or saline) were investigated using correspondence analysis.
There were significant differences in most of the structural traits, but in only one of the photosynthetic traits, between sites at the same altitude and between altitudes. The between-site differences could not be explained since site characteristics were not measured, but the between site differences were often species-dependent; a particular species might show its lowest value for a particular trait at the same site where another species showed the highest value for that trait. The between-altitude differences in structural trait values could be ascribed to the effect of greater wind speed at higher altitude (lower stature, tougher leaves and stems). High altitude plants have greater specific root length, probably a response to low soil nutrient status and hence a need for foraging roots. However, plants in saline coastal habitats also show a high specific root length, probably in response to the inhibitory effect of high salt concentration on nutrient and water uptake. All the species except Azorella selago, the archetypical vascular species of high altitude were more stunted and showed greater signs of stress at high altitude than at low altitude.
Native species tend to show greater values for those traits indicative of structural strength (tough, thick leaves, strong stems), and allocate a greater proportion of their biomass aboveground, than human-introduced alien species. Alien graminoids also have higher stomatal densities (but lower chlorophyll concentrations on a leaf area basis) than native species. There are no consistent differences in photosynthetic capacity between natives and aliens, except that native species tend to show a sharper photosynthetic response to increasing light at low levels, possibly an adaptation to the consistently low light regime at the island.
Maximum photosynthetic electron transport rate varies greatly (by an order of magnitude) between the island’s vascular species and by almost an order of magnitude between the bryophyte species. Species with high electron transport rate also tend to have a high effective quantum yield and show electron transport saturation at high light – all indicative of high photosynthetic capacity sun species, most of which are forbs. The shade-adapted, lowest photosynthetic capacity species…
Advisors/Committee Members: Smith, Valdon R., Stellenbosch University. Faculty of Science. Dept. of Botany and Zoology.
Subjects/Keywords: Marion Island plant characteristics; Island plants; UCTD
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APA (6th Edition):
Louw, A. (2016). Plant functional types on Marion Island. (Masters Thesis). Stellenbosch University. Retrieved from http://hdl.handle.net/10019.1/98483
Chicago Manual of Style (16th Edition):
Louw, Anche. “Plant functional types on Marion Island.” 2016. Masters Thesis, Stellenbosch University. Accessed January 26, 2021.
http://hdl.handle.net/10019.1/98483.
MLA Handbook (7th Edition):
Louw, Anche. “Plant functional types on Marion Island.” 2016. Web. 26 Jan 2021.
Vancouver:
Louw A. Plant functional types on Marion Island. [Internet] [Masters thesis]. Stellenbosch University; 2016. [cited 2021 Jan 26].
Available from: http://hdl.handle.net/10019.1/98483.
Council of Science Editors:
Louw A. Plant functional types on Marion Island. [Masters Thesis]. Stellenbosch University; 2016. Available from: http://hdl.handle.net/10019.1/98483
Stellenbosch University
24.
Kemp, Jurene Ellen.
Untangling mechanisms structuring insect diversity patterns in the Cape Floristic Region : the Restionaceae and their herbivores.
Degree: MSc, Botany and Zoology, 2014, Stellenbosch University
URL: http://hdl.handle.net/10019.1/96067
► ENGLISH ABSTRACT: Research into the patterns and drivers of insect diversity in the Cape Floristic Region (CFR) lags far behind that of plants. Here I…
(more)
▼ ENGLISH ABSTRACT: Research into the patterns and drivers of insect diversity in the Cape Floristic Region (CFR)
lags far behind that of plants. Here I sample insect herbivore communities on a dominant
plant family (Restionaceae), and use a spatially nested sampling design and network analysis
to evaluate the association between plant and insect diversity in the CFR. I find that plant
species richness predicts insect richness better than environmental factors. Turnover in insect
communities is strongly associated with turnover in plant (both species and phylogenetic)
communities at both local and regional sampling scales, suggesting insect host specificity.
Plant communities unsurprisingly show significant turnover at small spatial scales (i.e.
communities situated 0.1-3 km apart show significant turnover and may be tied to ecological
niches). Insects show a similar pattern, but the decrease in community overlap is more
gradual, suggesting many insects can utilise multiple (possibly closely related) hosts while
plants are tied to particular niches. The emergent structure of multiple interaction networks is
spatially and temporally invariant, despite high compositional change. However, the internal
structure of the networks shows variation (i.e. interactions show spatial and temporal
turnover). Seasonal interaction turnover is driven by a turnover in herbivores and by
herbivore host switching. Spatially the turnover in interactions is driven by simultaneous
turnover in both plants and insects, either suggesting that insects are host specific, or that
both groups exhibit parallel responses to environmental gradients. Spatial interaction turnover
is also driven by a turnover in plants, showing that many insects can utilise multiple (possibly
closely related) hosts and have wider distribution ranges than their host plants. Results point
toward insect host specificity, but probably not at the species level, as the primary mechanism
structuring insect communities associated with the Restionaceae in the CFR.
AFRIKAANSE OPSOMMING: Navorsing wat verband hou met die patrone en meganismes wat insekdiversiteit in the
Kaapse Blommeryk (KBR) hou nie pas met dié van plante nie. In hierdie studie neem ek
insekmonsters binne een van die dominante plantfamilies (Restionaceae), en gebruik ‘n
ruimtelik geneste ontwerp en netwerkanalise om die verbintenis tussen plant- en
insekdiversiteit te evalueer. Ek vind plantrykheid voorspel insekrykheid beter as enige
omgewingsfaktore. ‘n Omset in in insekgemeenskappe is sterk verbind aan ‘n omset in
plantgemeenskappe (beide spesie en filogenetiese) by beide plaaslik en vir die hele streek.
Hierdie dui op insekgasheerspesifisiteit. Plantgemeenskappe wys omset teen kort ruimtelike
skale (0.1-3 km). Insekte wys ‘n soortgelyke patron, maar die afname in oorvleueling tussen
gemeenskappe is meer geredelik. Dit dui dat insek meer as een gasheer kan gebruik, terwyl
plante streng tot sekere nisse verbind is. Die ontluikende struktuur van menigde
interaksienetwerke wys…
Advisors/Committee Members: Ellis, Allan George, Stellenbosch University. Faculty of Science. Dept. of Botany and Zoology..
Subjects/Keywords: Zoology; Dissertations – Zoology
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APA (6th Edition):
Kemp, J. E. (2014). Untangling mechanisms structuring insect diversity patterns in the Cape Floristic Region : the Restionaceae and their herbivores. (Masters Thesis). Stellenbosch University. Retrieved from http://hdl.handle.net/10019.1/96067
Chicago Manual of Style (16th Edition):
Kemp, Jurene Ellen. “Untangling mechanisms structuring insect diversity patterns in the Cape Floristic Region : the Restionaceae and their herbivores.” 2014. Masters Thesis, Stellenbosch University. Accessed January 26, 2021.
http://hdl.handle.net/10019.1/96067.
MLA Handbook (7th Edition):
Kemp, Jurene Ellen. “Untangling mechanisms structuring insect diversity patterns in the Cape Floristic Region : the Restionaceae and their herbivores.” 2014. Web. 26 Jan 2021.
Vancouver:
Kemp JE. Untangling mechanisms structuring insect diversity patterns in the Cape Floristic Region : the Restionaceae and their herbivores. [Internet] [Masters thesis]. Stellenbosch University; 2014. [cited 2021 Jan 26].
Available from: http://hdl.handle.net/10019.1/96067.
Council of Science Editors:
Kemp JE. Untangling mechanisms structuring insect diversity patterns in the Cape Floristic Region : the Restionaceae and their herbivores. [Masters Thesis]. Stellenbosch University; 2014. Available from: http://hdl.handle.net/10019.1/96067
Stellenbosch University
25.
Marais, Eugene.
Interspecific and temporal variation of condensed tannins and cyanide concentrations in potential dietary sources of extralimital giraffes (Giraffa camelopardalis) in the Karoo.
Degree: MSc, Botany and Zoology, 2019, Stellenbosch University
URL: http://hdl.handle.net/10019.1/105981
► ENGLISH ABSTRACT: During 2016 and 2018 four giraffe (Giraffa camelopardalis) mortalities occurred in the Karoo potentially caused by acute hydrogen cyanide poisoning. Plants have various…
(more)
▼ ENGLISH ABSTRACT: During 2016 and 2018 four giraffe (Giraffa camelopardalis) mortalities occurred in the Karoo potentially caused by acute hydrogen cyanide poisoning. Plants have various defence mechanisms to protect themselves against herbivory, including the production of secondary metabolites such as condensed tannins and hydrogen cyanide. This study quantified condensed tannin and hydrogen cyanide production in selected Karoo plant species that giraffe may browse, to assess the possibility of acute hydrogen cyanide poisoning and condensed tannin intoxification. Condensed tannins and hydrogen cyanide concentrations were explored in both spatial and temporal scales. The spatial assessment was performed at macro-scales (different locations within the Karoo), whereas temporal assessment was performed at seasonal scale. The effect of water availability and herbivory on condensed tannin production in Vachellia karroo trees was also investigated. Condensed tannin concentrations were high throughout seasons and did not differ significantly among the study sites in plant species giraffe primarily browse. In winter, V. karroo leaves were unavailable and secondary plant species increased in dietary importance. The most preferred plant species in the giraffes’ diet, V. karroo, contained high levels of condensed tannins in mature leaves as well as in new-growth plant tissue. Condensed tannin concentrations increased significantly in several evergreen tree species during winter, including Schotia afra var. afra and species of the Rhus genus, which may indicate an increase in dietary importance during winter season. Schotia afra var. afra contained lower condensed tannin concentrations than V. karroo throughout the study. Condensed tannin production increased significantly in three of the four treatment groups of V. karroo trees that received simulated herbivory regardless of the browsing intensity. Both treatment groups which received water, increased in nitrogen contentment, whereas trees from the browsed and not watered treatment decreased in nitrogen content value and palatability. The high condensed tannin concentrations seem to be a fixed defence response by Karoo plants to browsing, or a response when sufficient water is available. The high condensed tannin concentrations may reduce the available browse as giraffe and other herbivores may reject leaves high in condensed tannins. However, giraffe have the ability to partially degrade condensed tannins and will therefore not be as susceptible to tannin intoxification than other herbivores. The higher browsing pressure caused by giraffe may therefore be detrimental to other herbivores utilising the same plant species in the Karoo, that do not have the ability to degrade condensed tannins. Therefore, careful considerations should be taken when introducing large game species into the Karoo. Only focusing on vegetation composition and abundance may be insufficient in predicting carrying capacities in semi-arid environments such as the Karoo without taking chemical composition…
Advisors/Committee Members: Van Wyk, Johannes H., Truter, Christoff, Stellenbosch University. Faculty of Science. Dept. of Botany and Zoology..
Subjects/Keywords: Hydrogen cyanide production; Condensed tannin production; Giraffe – Feeding and feeds; Giraffe – Karoo; UCTD
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APA (6th Edition):
Marais, E. (2019). Interspecific and temporal variation of condensed tannins and cyanide concentrations in potential dietary sources of extralimital giraffes (Giraffa camelopardalis) in the Karoo. (Masters Thesis). Stellenbosch University. Retrieved from http://hdl.handle.net/10019.1/105981
Chicago Manual of Style (16th Edition):
Marais, Eugene. “Interspecific and temporal variation of condensed tannins and cyanide concentrations in potential dietary sources of extralimital giraffes (Giraffa camelopardalis) in the Karoo.” 2019. Masters Thesis, Stellenbosch University. Accessed January 26, 2021.
http://hdl.handle.net/10019.1/105981.
MLA Handbook (7th Edition):
Marais, Eugene. “Interspecific and temporal variation of condensed tannins and cyanide concentrations in potential dietary sources of extralimital giraffes (Giraffa camelopardalis) in the Karoo.” 2019. Web. 26 Jan 2021.
Vancouver:
Marais E. Interspecific and temporal variation of condensed tannins and cyanide concentrations in potential dietary sources of extralimital giraffes (Giraffa camelopardalis) in the Karoo. [Internet] [Masters thesis]. Stellenbosch University; 2019. [cited 2021 Jan 26].
Available from: http://hdl.handle.net/10019.1/105981.
Council of Science Editors:
Marais E. Interspecific and temporal variation of condensed tannins and cyanide concentrations in potential dietary sources of extralimital giraffes (Giraffa camelopardalis) in the Karoo. [Masters Thesis]. Stellenbosch University; 2019. Available from: http://hdl.handle.net/10019.1/105981
Stellenbosch University
26.
Basson, Christine Helene.
Thermal adaptation in the lizard Cordylus oelofseni : physiological and behavioural responses to temperature variation.
Degree: MSc, Botany and Zoology, 2013, Stellenbosch University
URL: http://hdl.handle.net/10019.1/95471
► ENGLISH ABSTRACT: As ectotherms, lizards are particularly vulnerable to changes in the thermal landscape and face extinction risk if they lack the capacity to rapidly…
(more)
▼ ENGLISH ABSTRACT: As ectotherms, lizards are particularly vulnerable to changes in the thermal landscape and face extinction risk if they lack the capacity to rapidly adapt or behaviourally mitigate increasingly altered thermal environments. Theoretical models that predict lizards‟ response to climate change often fail to take into account the thermal characteristics of the microenvironment, the ability of lizards to behaviourally buffer climate variation in the habitat and the plastic nature of both behaviour and physiology over ecologically relevant time-scales. Here, I address this major knowledge gap using two separate research chapters in an experimental physiology approach. In Chapter 1, I investigated the temperature-dependence and plasticity of resting metabolic rate, water-loss rate and preferred body temperature of Cordylus oelofseni at several temporal scales (within and between seasons) and incorporated field observations to acquire a better understanding of this species‟ adaptive potential to buffer thermal changes in the habitat. Cordylus oelofseni showed plasticity of both behaviour and physiology in response to thermal acclimation, but relied on distinct strategies depending on the time-scale investigated. These results highlighted the complexity of underlying mechanisms used by these organisms to buffer temperature variation. In Chapter 2, I used an experimental approach to examine the energetic costs of thermoregulation in C. oelofseni and test the cost-benefit model of thermoregulation. This model‟s primary prediction states that lizards should thermoregulate carefully only when the associated costs are low. Using four enclosures that simulated different thermal qualities (temporal and spatial distributions of operative temperatures) in the habitat, I found limited support for the cost-benefit model. Lizards in the low-quality heterogeneous enclosures invested the same energetic effort and thermoregulated with similar overall accuracy as lizards in the high-quality heterogeneous enclosure. The costs incurred were not necessarily energetic, but reflected missed opportunities (e.g. less time to forage), something that, along with important interaction effects with body mass, deserves further attention when testing this model. Together, these results illustrate the importance of incorporating ecological reality at various time and spatial scales in order to make relevant predictions regarding the fate of lizards with projected climate change.
AFRIKAANSE OPSOMMING: As ektotermiese diere, is akkedisse veral sensitief vir veranderinge in die termiese landskap en staar uitsterwingsrisiko in die gesig as hulle nie die vermoë het om vinnig aan te pas of gedragsveranderinge te maak in omgewings wat toenemend verwarm nie. Teoretiese modelle wat akkedisse se reaksie op klimaatsverandering voorspel, neem dikwels nie die termiese eienskappe van die mikro-omgewing, die vermoë van akkedisse om met gedragsveranderinge klimaat variasie in die habitat te buffer en die plastieke aard van beide gedrag en fisiologie…
Advisors/Committee Members: Clusella-Trullas, Susana, Stellenbosch University. Faculty of Science. Dept. of Botany and Zoology..
Subjects/Keywords: Lizard Cordylus oelofseni – Thermal adaptation; Lizard Cordylus oelofseni – Metabolism; Lizard Cordylus oelofseni – Physiological and behavioural responses; UCTD
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APA (6th Edition):
Basson, C. H. (2013). Thermal adaptation in the lizard Cordylus oelofseni : physiological and behavioural responses to temperature variation. (Masters Thesis). Stellenbosch University. Retrieved from http://hdl.handle.net/10019.1/95471
Chicago Manual of Style (16th Edition):
Basson, Christine Helene. “Thermal adaptation in the lizard Cordylus oelofseni : physiological and behavioural responses to temperature variation.” 2013. Masters Thesis, Stellenbosch University. Accessed January 26, 2021.
http://hdl.handle.net/10019.1/95471.
MLA Handbook (7th Edition):
Basson, Christine Helene. “Thermal adaptation in the lizard Cordylus oelofseni : physiological and behavioural responses to temperature variation.” 2013. Web. 26 Jan 2021.
Vancouver:
Basson CH. Thermal adaptation in the lizard Cordylus oelofseni : physiological and behavioural responses to temperature variation. [Internet] [Masters thesis]. Stellenbosch University; 2013. [cited 2021 Jan 26].
Available from: http://hdl.handle.net/10019.1/95471.
Council of Science Editors:
Basson CH. Thermal adaptation in the lizard Cordylus oelofseni : physiological and behavioural responses to temperature variation. [Masters Thesis]. Stellenbosch University; 2013. Available from: http://hdl.handle.net/10019.1/95471
Stellenbosch University
27.
Randle, Matilda Rose.
Effects of warming on the early establishment of an African savanna tree.
Degree: MSc, Botany and Zoology, 2019, Stellenbosch University
URL: http://hdl.handle.net/10019.1/107168
► ENGLISH ABSTRACT: This study investigates the interactive effects of atmospheric warming and the presence of a C4 grass sward on the growth and mortality of…
(more)
▼ ENGLISH ABSTRACT: This study investigates the interactive effects of atmospheric warming and the presence of a C4 grass sward on the growth and mortality of establishing savanna tree seedlings (Senegalia nigrescens (Oliv.) P. J. H. Hurter). Atmospheric warming is one of the major drivers of global vegetation change, but has been little studied in tropical African systems. In cool temperature systems of the mid- to high –latitudes, where plant growth is predominantly controlled by climatic factors, warming has beenshown to drive an increase in plant growth and establishment. In systems of the mid – to low – latitudes, such as sub-tropical savannas, the potential role of warming is not well known, and the vegetation structure and functioning of these systems is controlled by the interacting impacts of fire, herbivory and climate. Wildfire and herbivory limit the seedling and sapling demographic stages of savanna trees. This stage is expected to be most vulnerable to warming because seedlings are sensitive to fluctuations in temperature and are highly dependent on water availability, a resource that is competed for strongly by C4 grasses. Furthermore, C4 grasses are unlikely to be as adversely affected by warming as C3 seedlings, due to differences in their photosynthetic pathways. Based on these arguments, this study tests the main hypothesis that there is an adverse interactive effect of warming and grass competition on tree seedling establishment in savannas. In order to test this hypothesis, I carried out a field experiment at Wits Rural Facility in Limpopo Province, South Africa during the 2017/18 growing season. Using passive open-topped, polycarbonate warming chambers, seedlings were warmed on average, by 1-2°C. Soil and plant water content were unaffected by warming but the presence of grass significantly reduced the relative water content of the leaves of establishing seedlings, suggesting competition for water between the different growth forms. Seedling growth rate was unaffected by warming when grown without C4 grasses, but a significant decline was shown by those grown with grasses above a daytime temperature threshold of 30°C. Likewise, seedlings grown with grasses suffered a 65% reduction in survivorship when warmed but those grown in the absence of grass suffered only a 15% reduction in survivorship. The results of this study therefore show that warming and the presence of grasses had an adverse additive effect on seedling survivorship, through which warming enhanced the dehydrating effect of competing grass on establishing seedlings, thus confirming the primary hypothesis. I propose that the cumulative stresses of carbon imbalance due to warming and grass competition for soil water drove this decline in tree seedling growth, resulting in higher seedling mortality with the implication of reduced successful establishment events under warmer conditions. This study makes an important contribution to understanding the impact of warming on African savanna species, in that it suggests a future decline in tree…
Advisors/Committee Members: Midgley, Guy F., Stevens, Nicola, Stellenbosch University. Faculty of Science. Dept. of Botany and Zoology..
Subjects/Keywords: Global warming – Environmental aspects; Savanna plants – Climatic factors – Africa; Grasslands – Conservation; Trees – Seedling – Growth; UCTD
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APA (6th Edition):
Randle, M. R. (2019). Effects of warming on the early establishment of an African savanna tree. (Masters Thesis). Stellenbosch University. Retrieved from http://hdl.handle.net/10019.1/107168
Chicago Manual of Style (16th Edition):
Randle, Matilda Rose. “Effects of warming on the early establishment of an African savanna tree.” 2019. Masters Thesis, Stellenbosch University. Accessed January 26, 2021.
http://hdl.handle.net/10019.1/107168.
MLA Handbook (7th Edition):
Randle, Matilda Rose. “Effects of warming on the early establishment of an African savanna tree.” 2019. Web. 26 Jan 2021.
Vancouver:
Randle MR. Effects of warming on the early establishment of an African savanna tree. [Internet] [Masters thesis]. Stellenbosch University; 2019. [cited 2021 Jan 26].
Available from: http://hdl.handle.net/10019.1/107168.
Council of Science Editors:
Randle MR. Effects of warming on the early establishment of an African savanna tree. [Masters Thesis]. Stellenbosch University; 2019. Available from: http://hdl.handle.net/10019.1/107168
Stellenbosch University
28.
David, Andrew Anthony.
An integrated larval development and population genetics approach for predicting the establishment and dispersal potential of a recently introduced polychaete (Annelida: Spionidae) in southern Africa.
Degree: PhD, Botany and Zoology, 2015, Stellenbosch University
URL: http://hdl.handle.net/10019.1/96594
► ENGLISH ABSTRACT: Boccardia proboscidea is a recently introduced polychaete in South Africa (SA) where it is a notorious pest of commercially reared abalone. The species…
(more)
▼ ENGLISH ABSTRACT: Boccardia proboscidea is a recently introduced polychaete in South Africa (SA) where it is a notorious pest of commercially reared abalone. The species was restricted to
abalone farms distributed in three biogeographic regions up until 2011, when the first
wild population was detected in the southern part of the country. If Boccardia proboscidea becomes invasive, it could pose a threat to the intertidal marine ecosystem of SA. The overarching aim of this thesis was therefore to predict the establishment and
dispersal potential of B. proboscidea. The first objective was to assess the feasibility of
using a closely related species to ground truth in the predictions. In Chapter 2,
reproductive experiments were integrated with molecular studies to show that the nonindigenous
oyster pest Polydora hoplura, like B. proboscidea can produce both planktotrophic and adelphophagic larvae (poecilogonous development). Due to a similar
reproductive strategy along with its status as an aquaculture pest, P. hoplura was
chosen as the “predictor” species. In Chapter 3 I investigated the effect of temperature
on larval development of P. hoplura and B. proboscidea using temperature regimes
reflective of the SA coast to determine establishment potential. Results showed that
temperature significantly affected survivorship and developmental rate of planktotrophic
and adelphophagic larvae for both species. For P. hoplura, survivorship of both larval
types was highest at the intermediate to high temperature treatments (21 and 24°C) and
was generally lower at the lower temperatures (12 and 17°C). Boccardia proboscidea
exhibited a difference in survival optima where low temperatures favoured high
planktotroph survival but low adelphophagic larval survival. Conversely, increased
temperatures favoured high adelphophagic larval survival but low planktotroph survival
and this was most likely driven by increased rates of sibling cannibalism. There was also a positive relationship between temperature and developmental rate for both larval types of both species. Polydora hoplura’s response to experimental temperatures is
congruent with its present distribution. Based on this I predicted that B. proboscidea
should become established along a large section of the SA coast and differences in
survival optima may also facilitate its establishment in colder waters where P. hoplura
appears to be absent. In Chapter 4, I investigated the phylogeography of P. hoplura
using mtDNA (Cyt b) and nDNA (ATPSα) gene fragments. Results showed genetic
connectivity among all sampling sites distributed across two biogeographic regions. I
hypothesized that the low genetic structure observed was likely due to anthropogenic
dispersal mechanisms rather than natural dispersal. Finally in Chapter 5, I discussed the
potential for natural dispersal of B. proboscidea. Based on temperature-specific
planktonic larval duration and current velocities along the SA coast, B. proboscidea
could potentially cover hundreds of kilometres in a…
Advisors/Committee Members: Simon, Carol A., Matthee, Conrad A., Stellenbosch University. Faculty of Science. Dept. of Botany and Zoology..
Subjects/Keywords: Abalone farming – South Africa; Commercially reared abalone – Diseases and pests; Boccardia proboscidea – South Africa; Establishment and dispersal potential of Boccardia proboscidea; Marine ecology – South Africa; UCTD
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APA (6th Edition):
David, A. A. (2015). An integrated larval development and population genetics approach for predicting the establishment and dispersal potential of a recently introduced polychaete (Annelida: Spionidae) in southern Africa. (Doctoral Dissertation). Stellenbosch University. Retrieved from http://hdl.handle.net/10019.1/96594
Chicago Manual of Style (16th Edition):
David, Andrew Anthony. “An integrated larval development and population genetics approach for predicting the establishment and dispersal potential of a recently introduced polychaete (Annelida: Spionidae) in southern Africa.” 2015. Doctoral Dissertation, Stellenbosch University. Accessed January 26, 2021.
http://hdl.handle.net/10019.1/96594.
MLA Handbook (7th Edition):
David, Andrew Anthony. “An integrated larval development and population genetics approach for predicting the establishment and dispersal potential of a recently introduced polychaete (Annelida: Spionidae) in southern Africa.” 2015. Web. 26 Jan 2021.
Vancouver:
David AA. An integrated larval development and population genetics approach for predicting the establishment and dispersal potential of a recently introduced polychaete (Annelida: Spionidae) in southern Africa. [Internet] [Doctoral dissertation]. Stellenbosch University; 2015. [cited 2021 Jan 26].
Available from: http://hdl.handle.net/10019.1/96594.
Council of Science Editors:
David AA. An integrated larval development and population genetics approach for predicting the establishment and dispersal potential of a recently introduced polychaete (Annelida: Spionidae) in southern Africa. [Doctoral Dissertation]. Stellenbosch University; 2015. Available from: http://hdl.handle.net/10019.1/96594
Stellenbosch University
29.
Johnson, Christopher Michael.
Flowers with style : the role of pollinators in the origin and maintenance of Proteaceae diversity with a focus on the genus Leucospermum.
Degree: PhD, Botany and Zoology, 2015, Stellenbosch University
URL: http://hdl.handle.net/10019.1/96722
► ENGLISH ABSTRACT: It is believed that angiosperm diversification can regularly be explained by adaptation to pollinators. This may result from a shift to a new…
(more)
▼ ENGLISH ABSTRACT: It is believed that angiosperm diversification can regularly be explained by adaptation to pollinators. This may result from a shift to a new pollinator, recruitment of a supplemental pollinator, employing the traditional pollinator in a new way, or relying less on pollinators altogether and instead placing a stronger emphasis on self-pollination. Diversification can transpire when a population finds itself in a new habitat lacking the traditional pollinator or when taxa overlap in the utilization of a shared pollinator resource. Competition between taxa that utilize the same pollinator ceases once pollinator partitioning is sufficiently achieved if taxa do not compete for pollinator visits. Therefore, pollinators can also be a determinant of angiosperm community composition in addition to drivers of speciation. Throughout this thesis I examine how angiosperms adapt to pollinators as a resource, how pollinators drive speciation, and how pollinators maintain communities by focusing on the southern African genus Leucospermum (Proteaceae).
Adaptation to fluctuations in the pollinator mosaic can drive diversification of floral morphology and denotes the onset of speciation. In Chapter 2 we examine pollinator driven adaptive divergence between two closely related Leucospermum taxa that have distinct floral morphologies and employ different pollinators. We suggest that these two varieties are ecotypes that originated through adaptation to different pollinators.
Angiosperms in the Cape Floristic Region often evolve elaborate features that allow them to utilize atypical pollinators. In Chapter 3 we explore remarkable adaptations for non-flying mammal pollination in an endangered Leucospermum species. We show that unique nectar characteristics accommodate gerbil and mice pollinators, that proximity to the ground does not influence seed production, and that frequent grooming by non-flying mammals quickly diminishes the pollen available for outcrossing.
In Chapters 2 and 3 we show that pollinators can select for floral traits as well as drive speciation. But how often do pollinator shifts occur? What traits must evolve to utilize specific functional groups of pollinators? What morphological features and/or pollination modes encourage autonomous self-pollination? To answer such questions one must incorporate phylogenetics into analyses to account for relatedness among taxa. In Chapter 4 we construct the first Leucospermum phylogeny and use it to test for correlated evolution between floral morphology, pollination mode, and autonomous selfing using 7 floral measures and 10 functional groups of pollinators. We show that floral traits are highly correlated with pollination modes and that the evolution of autonomous selfing is coupled with the bird pollination syndrome.
Along with being drivers of floral diversity, pollinators can also act to shape and maintain floral communities. Since pollinators are a limited resource, pollinators act as ecological filters by restricting certain species from a community…
Advisors/Committee Members: Pauw, Anton, Stellenbosch University. Faculty of Science. Dept. of Botany and Zoology..
Subjects/Keywords: Flowers – Pollination; Proteaceae – Pollen; Leucospermum (Proteaceae) species; Pollinators as a resource; UCTD
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APA ·
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APA (6th Edition):
Johnson, C. M. (2015). Flowers with style : the role of pollinators in the origin and maintenance of Proteaceae diversity with a focus on the genus Leucospermum. (Doctoral Dissertation). Stellenbosch University. Retrieved from http://hdl.handle.net/10019.1/96722
Chicago Manual of Style (16th Edition):
Johnson, Christopher Michael. “Flowers with style : the role of pollinators in the origin and maintenance of Proteaceae diversity with a focus on the genus Leucospermum.” 2015. Doctoral Dissertation, Stellenbosch University. Accessed January 26, 2021.
http://hdl.handle.net/10019.1/96722.
MLA Handbook (7th Edition):
Johnson, Christopher Michael. “Flowers with style : the role of pollinators in the origin and maintenance of Proteaceae diversity with a focus on the genus Leucospermum.” 2015. Web. 26 Jan 2021.
Vancouver:
Johnson CM. Flowers with style : the role of pollinators in the origin and maintenance of Proteaceae diversity with a focus on the genus Leucospermum. [Internet] [Doctoral dissertation]. Stellenbosch University; 2015. [cited 2021 Jan 26].
Available from: http://hdl.handle.net/10019.1/96722.
Council of Science Editors:
Johnson CM. Flowers with style : the role of pollinators in the origin and maintenance of Proteaceae diversity with a focus on the genus Leucospermum. [Doctoral Dissertation]. Stellenbosch University; 2015. Available from: http://hdl.handle.net/10019.1/96722
Stellenbosch University
30.
De Jager, Marinus Louis.
The role of pollinators in generating and maintaining floral polymorphism : phylogeographic and behavioural aspects.
Degree: PhD, Botany and Zoology, 2013, Stellenbosch University
URL: http://hdl.handle.net/10019.1/79883
► Pollinators play a fundamental role in floral evolution. They can exert selection on the flowers they visit in a plethora of different ways, ranging from…
(more)
▼ Pollinators play a fundamental role in floral evolution. They can exert selection on the flowers they visit in a
plethora of different ways, ranging from innate floral preferences to differences in body size and shape and
behavioural elements such as flower constancy and learning capacity. Since different pollinators exhibit
differences in these characters, shifts between pollinating species are often considered the most likely drivers
of floral diversification. While many lines of evidence support this claim, numerous angiosperms pollinated
by a single species also exhibit floral variation. Throughout my thesis, I explore and investigate floral
diversification in such species in the absence of pollinator shifts.
In Chapter 2, I investigate variation in the preference of conspecific male and female pollinators for
the floral traits of a sexually deceptive daisy that comprises distinct floral forms. I show that its pollinator
exhibits gender-specific variation in floral preferences, and that some floral forms have specialized on the
male pollinator. This chapter thus illustrates the importance of intraspecific variation in pollinator preference
for floral diversification, an underappreciated mechanism in this field of research.
The innate preferences of pollinators are likely to have a genetic basis, especially innate preferences
that govern mate choice. Genetic structure within the pollinators of sexually deceptive plants, which mimic
female insects to achieve pollination, may thus provide an important source of selection on the plants they
pollinate. This depends on an association between genetic divergence and divergent mate preferences, and I
explore this intriguing idea in Chapter 3. While pollinators associated with sexually deceptive floral forms
did exhibit significant genetic structuring, male pollinators from different phylogeographic clades all
exhibited preference for the same sexually deceptive floral form, thus rejecting this hypothesis.
Another behavioural attribute of pollinators that may affect floral evolution, particularly in deceptive
plant species, is learning ability. Studies on sexually deceptive orchids often report that male pollinators tend
to avoid sexually deceptive flowers with experience. In Chapter 4, I systematically investigate learning
abilities within male pollinators and the costs they suffer on sexually deceptive floral forms that vary in
deceptiveness. Results reveal a positive relationship between the level of floral deceptiveness and the
4
associated mating costs that deceived males suffer. Pollinator learning, however, appears to occur only on the
most deceptive floral forms, suggesting a link between the costs suffered to the occurrence of learning.
In Chapter 4, I systematically investigate learning
abilities within male pollinators and the costs they suffer on sexually deceptive floral forms that vary in
deceptiveness. Results reveal a positive relationship between the level of floral deceptiveness and the associated mating costs that deceived…
Advisors/Committee Members: Ellis, Allan George, Stellenbosch University. Faculty of Science. Dept. of Botany and Zoology..
Subjects/Keywords: Botany; Dissertations – Botany
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APA (6th Edition):
De Jager, M. L. (2013). The role of pollinators in generating and maintaining floral polymorphism : phylogeographic and behavioural aspects. (Doctoral Dissertation). Stellenbosch University. Retrieved from http://hdl.handle.net/10019.1/79883
Chicago Manual of Style (16th Edition):
De Jager, Marinus Louis. “The role of pollinators in generating and maintaining floral polymorphism : phylogeographic and behavioural aspects.” 2013. Doctoral Dissertation, Stellenbosch University. Accessed January 26, 2021.
http://hdl.handle.net/10019.1/79883.
MLA Handbook (7th Edition):
De Jager, Marinus Louis. “The role of pollinators in generating and maintaining floral polymorphism : phylogeographic and behavioural aspects.” 2013. Web. 26 Jan 2021.
Vancouver:
De Jager ML. The role of pollinators in generating and maintaining floral polymorphism : phylogeographic and behavioural aspects. [Internet] [Doctoral dissertation]. Stellenbosch University; 2013. [cited 2021 Jan 26].
Available from: http://hdl.handle.net/10019.1/79883.
Council of Science Editors:
De Jager ML. The role of pollinators in generating and maintaining floral polymorphism : phylogeographic and behavioural aspects. [Doctoral Dissertation]. Stellenbosch University; 2013. Available from: http://hdl.handle.net/10019.1/79883
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