University of Oklahoma
Environment and interspecific interactions at the margin of species ranges: a spatial analysis of forest communities.
Degree: PhD, 2017, University of Oklahoma
Problem: Species’ geographic ranges are determined, in part, by suitable environmental conditions, the ability to reach sites possessing those environmental conditions, and the capability to survive interactions with other species until reproductive age. Species’ geographic ranges and community composition have been related to environmental conditions frequently, to dispersal limitation infrequently, and rarely to biotic interactions. This dissertation utilizes spatially explicit analysis to further elucidate the effect of geography on community composition, beta diversity, interspecific interactions, and the intersections of them on species’ geographic ranges. Contradictory evidence suggests that interspecific interactions become either more facilitative or competitive with increasing stress, however results appear to be affected by the scale of study. Therefore, I performed a regional scale study to analyze interspecific interactions across a regional stress gradient, the proximity to a species’ range margin.
Methods: Bottomland and upland forests consisting of 91 species across 307 sites were analyzed across spatial and environmental gradients. Sites were separated on the basis of species presence using a Nonmetric Multidimensional Scaling ordination and grouped using an agglomerative hierarchical clustering algorithm. To explain variance in community composition, climate, spatial, and edaphic variables were related to species presence across sites with a Redundancy Analysis ordination which uses multiple Canonical Correspondence Analyses. Species’ range margins were delineated using species occurrence data from the Forest Inventory and Analysis with MaxEnt modeling software. In order to test how interspecific interactions change across species’ ranges, a spatially explicit model assessing co-occurrence in groups of nearest neighbor sites was created using Python programming language. Interspecific interactions were subsequently compared to randomly generating communities.
Results: Species within site groups respond primarily to average annual precipitation and secondarily to the standard deviation in monthly precipitation. Sites are more aggregated in environmental space than physical space. Variation in community composition is best explained by climatic variables (22%) followed by spatial (9.9%) and edaphic (9.8%) variables. Beta diversity is significantly positively correlated with climate distance, mammal and bird beta diversity, the variance in distances to species’ range margins, and soil texture distance between sites. Net interspecific interactions monotonically shift from competitive to facilitative with proximity to species’ range margins. Species exhibit monotonic, unimodal, and multimodal relationships between net interaction intensity and proximity to their respective range margins in approximately equal proportions. As conditions become more favorable, species within a genus interact more competitively than species of different genera. Both locally rare and locally dominant species experience…
Advisors/Committee Members: Hoagland, Bruce (advisor), Greene, Scott (committee member), Koch, Jennifer (committee member), McCarthy, Heather (committee member), Souza, Lara (committee member).
Subjects/Keywords: community composition; species interactions; range margins; biogeography
to Zotero / EndNote / Reference
APA (6th Edition):
Hardwick, D. (2017). Environment and interspecific interactions at the margin of species ranges: a spatial analysis of forest communities. (Doctoral Dissertation). University of Oklahoma. Retrieved from http://hdl.handle.net/11244/50747
Chicago Manual of Style (16th Edition):
Hardwick, Daryn. “Environment and interspecific interactions at the margin of species ranges: a spatial analysis of forest communities.” 2017. Doctoral Dissertation, University of Oklahoma. Accessed August 23, 2017.
MLA Handbook (7th Edition):
Hardwick, Daryn. “Environment and interspecific interactions at the margin of species ranges: a spatial analysis of forest communities.” 2017. Web. 23 Aug 2017.
Hardwick D. Environment and interspecific interactions at the margin of species ranges: a spatial analysis of forest communities. [Internet] [Doctoral dissertation]. University of Oklahoma; 2017. [cited 2017 Aug 23].
Available from: http://hdl.handle.net/11244/50747.
Council of Science Editors:
Hardwick D. Environment and interspecific interactions at the margin of species ranges: a spatial analysis of forest communities. [Doctoral Dissertation]. University of Oklahoma; 2017. Available from: http://hdl.handle.net/11244/50747