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You searched for +publisher:"Victoria University of Wellington" +contributor:("Hoffmann, Ben"). Showing records 1 – 2 of 2 total matches.

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Victoria University of Wellington

1. Cooling, Meghan Dawn. Population dynamics and pathogens of the invasive yellow crazy ant (Anoplolepis gracilipes) in Arnhem Land, Australia.

Degree: 2015, Victoria University of Wellington

Though many populations of introduced species have been observed to collapse, the reasons behind these declines are seldom investigated. Anoplolepis gracilipes is considered among one of the top six most economically and ecologically damaging invasive ant species in the world. However, introduced populations of A. gracilipes have been observed to decline. My overall aims in this thesis were to document A. gracilipes population declines, to investigate the possibility that pathogens were playing a role in the observed population declines, and to identify putative pathogens infecting A. gracilipes as potential candidates for biocontrol agents. I documented the observed A. gracilipes population declines that were the driving force for this project. I detailed large-scale reductions in the spatial extent of four populations with before and after survey data. I also presented data on three populations that were recorded as present, but disappeared before they could be spatially delimited. I speculated on the possible reasons for these declines and explained why I do not think other explanations are likely. I then investigated the hypothesis that a pathogen or parasite is affecting A. gracilipes queens in declining Arnhem Land populations. I did this in three ways: 1) based on preliminary findings, I looked at the effect of an artificial fungal infection on A. gracilipes reproduction. I compared reproductive output between control colonies and those treated with either a fungal entomopathogen (Metarhizium anisopliae) or fungicidal antibiotics. There was no correlation between either treatment and the number of eggs, larvae, pupae or males a colony produced after 70 days. I found queen number had no effect on colony reproductive output, suggesting that queens are able to adjust their egg-laying rate in the presence of other queens. I found no evidence that M. anisopliae affected reproductive output at the tested concentrations; 2) I explored the hypothesis that a pathogen that kills or affects the reproductive output of A. gracilipes queens is the mechanism or reason behind the population declines. I measured queen number per nest, egg-laying rate, fecundity and fat content and compared them between sites in different stages of decline or expansion (population types, consisting of low, medium and high-density populations). I discovered that 23% of queens had melanized nodules, a cellular immune response in insects, in their ovaries or fat bodies. The presence of nodules was correlated with a 22% decrease in the number of oocytes per ovary; however, nodule presence was not associated with population type, suggesting that though there are clearly pathogens or parasites capable of penetrating the cuticle of A. gracilipes, they are unlikely to be responsible for the observed population declines; 3) I compared microbial communities (bacteria and viruses) between queens from different population types. I found viral sequences that match to the Dicistroviridae family of viruses in low and medium-density populations. I found no… Advisors/Committee Members: Lester, Phil, Hoffmann, Ben.

Subjects/Keywords: Yellow crazy ant; Populations declines; Pathogens

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Cooling, M. D. (2015). Population dynamics and pathogens of the invasive yellow crazy ant (Anoplolepis gracilipes) in Arnhem Land, Australia. (Doctoral Dissertation). Victoria University of Wellington. Retrieved from http://hdl.handle.net/10063/5032

Chicago Manual of Style (16th Edition):

Cooling, Meghan Dawn. “Population dynamics and pathogens of the invasive yellow crazy ant (Anoplolepis gracilipes) in Arnhem Land, Australia.” 2015. Doctoral Dissertation, Victoria University of Wellington. Accessed July 10, 2020. http://hdl.handle.net/10063/5032.

MLA Handbook (7th Edition):

Cooling, Meghan Dawn. “Population dynamics and pathogens of the invasive yellow crazy ant (Anoplolepis gracilipes) in Arnhem Land, Australia.” 2015. Web. 10 Jul 2020.

Vancouver:

Cooling MD. Population dynamics and pathogens of the invasive yellow crazy ant (Anoplolepis gracilipes) in Arnhem Land, Australia. [Internet] [Doctoral dissertation]. Victoria University of Wellington; 2015. [cited 2020 Jul 10]. Available from: http://hdl.handle.net/10063/5032.

Council of Science Editors:

Cooling MD. Population dynamics and pathogens of the invasive yellow crazy ant (Anoplolepis gracilipes) in Arnhem Land, Australia. [Doctoral Dissertation]. Victoria University of Wellington; 2015. Available from: http://hdl.handle.net/10063/5032


Victoria University of Wellington

2. Gruber, Monica Alexandra Maria. Genetic Factors Associated with Variation in Abundance of the Invasive Yellow Crazy Ant (Anoplolepis gracilipes).

Degree: 2012, Victoria University of Wellington

A key component of successful invasion is the ability of an introduced population to reach sufficient abundance to persist, spread, and alter or dominate the recipient biological community. Genetic diversity is one of many factors that may contribute to population dynamics, but has important ramifications for biological fitness, and thus invasion success in the long term. I explored genetic factors associated with variation in abundance (i.e., differential invasion success) of the yellow crazy ant Anoplolepis gracilipes in the Indo-Pacific region, primarily focussing on Arnhem Land in Australia's Northern Territory. I explored five aspects that I hypothesised could contribute to variation in the abundance of this ant: 1) I investigated the unusual reproductive mode of A. gracilipes, and tested whether it involved dependent-lineage genetic caste determination (DL GCD) in Arnhem Land. In DL GCD systems populations require hybridisation between genetically distinct groups to produce both reproductive and worker castes. Asymmetry in the ratio of different lineages may result in low abundance and population collapse. I found no evidence for a DL GCD system in A. gracilipes, and thus its abundance in Arnhem Land does not appear to be constrained by any lineage ratio asymmetry. Worker reproduction (either of males or asexual production of other workers) also appeared unlikely. The reproductive mode of the species remains fascinating but enigmatic; 2) I explored whether multiple source populations were responsible for the observed variation in abundance in Arnhem Land (i.e., is abundance associated with propagule pressure, or populations from different sources), and if the population has diverged since introduction. The A. gracilipes population in Arnhem Land stemmed from a single source, and thus propagule pressure was apparently not responsible for variation in abundance. In contrast to many invasive ants, population divergence has occurred since introduction; 3) I tested the hypotheses that genetic variation was associated with variation in abundance in Arnhem Land, and that ecological success was density-dependent. While the population divergence found in Chapter 3 was not related to variation in abundance, genotypic diversity was higher in more abundant nest clusters. These more abundant nest clusters were in turn associated with lower native ant species diversity, and a difference in composition of the invaded ant community (i.e., greater ecological success); 4) I revisited the invasion of the yellow crazy ant in Tokelau to determine whether a haplotype that was linked to greater abundance and dominance of the ant community has increased in distribution. Although ants of the inferred dominant haplotype were implicated in most new invasions, their abundance was substantially lower than previously observed in Tokelau; 5) I conducted a preliminary analysis of the metagenomic diversity of A. gracilipes endogenous parasites and symbionts among populations from Christmas Island, Okinawa, Samoa and Arnhem Land. Bacterial… Advisors/Committee Members: Lester, Phil, Ritchie, Peter, Hoffmann, Ben.

Subjects/Keywords: Genetic diversity; Invasion success; Social insects

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Gruber, M. A. M. (2012). Genetic Factors Associated with Variation in Abundance of the Invasive Yellow Crazy Ant (Anoplolepis gracilipes). (Doctoral Dissertation). Victoria University of Wellington. Retrieved from http://hdl.handle.net/10063/2290

Chicago Manual of Style (16th Edition):

Gruber, Monica Alexandra Maria. “Genetic Factors Associated with Variation in Abundance of the Invasive Yellow Crazy Ant (Anoplolepis gracilipes).” 2012. Doctoral Dissertation, Victoria University of Wellington. Accessed July 10, 2020. http://hdl.handle.net/10063/2290.

MLA Handbook (7th Edition):

Gruber, Monica Alexandra Maria. “Genetic Factors Associated with Variation in Abundance of the Invasive Yellow Crazy Ant (Anoplolepis gracilipes).” 2012. Web. 10 Jul 2020.

Vancouver:

Gruber MAM. Genetic Factors Associated with Variation in Abundance of the Invasive Yellow Crazy Ant (Anoplolepis gracilipes). [Internet] [Doctoral dissertation]. Victoria University of Wellington; 2012. [cited 2020 Jul 10]. Available from: http://hdl.handle.net/10063/2290.

Council of Science Editors:

Gruber MAM. Genetic Factors Associated with Variation in Abundance of the Invasive Yellow Crazy Ant (Anoplolepis gracilipes). [Doctoral Dissertation]. Victoria University of Wellington; 2012. Available from: http://hdl.handle.net/10063/2290

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