Browsing by Subject "Community assembly"
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Item The interface between metacommunity ecology and microevolution in freshwater zooplankton(2009-12) Pantel, Jelena Holly; Leibold, Mathew A.; Juenger, Thomas E.; Hawkes, Christine; Bolnick, Daniel I.; Caceres, CarlaIn many habitats, species’ traits correspond strongly to local environmental conditions. The cause of this pattern may be in-situ evolution, where initially mal-adapted resident species evolved traits that increased their fitness. Alternatively, species with suitable traits may have colonized the focal habitat and replaced resident species. Since theories in the fields of evolutionary biology and community ecology developed independently, few guidelines tell us when to expect evolutionary adaptation or ecological species replacement as the primary driver of species and trait composition in a given habitat. The goal of my dissertation research was to explain how evolutionary adaptation and ecological species replacement together determine the composition of pond zooplankton communities. I combined theoretical models with thorough surveys of natural pond communities and manipulative experiments. I discovered that one particular zooplankton species, Daphnia pulex, evolved to have different trait values in ponds with different environments. The evolutionary divergence within D. pulex profoundly affected its ecological interactions with other zooplankton species. D. pulex populations diverged from one another so much that they differed in their ability to successfully colonize ponds full of competing zooplankton species. I also used a computer simulation model to determine when a community’s trait changes were explained by evolutionary adaptation or ecological species replacement. The dispersal rate of species among habitats and the amount of genetic variance within these species both influenced adaptive trait change in a community. The group of research studies that indicate evolutionary and ecological processes operate on a similar time scale is small but growing. My dissertation research provides another crucial demonstration that evolution within individual species, such as D. pulex, influences their community ecological interactions with other species. I also identified key parameters (dispersal rate among and genetic variance within species) that may help biologists predict whether evolution or ecological species replacement explained adaptive trait change. My projects mostly concern the community and trait distributions that result from the assembly of species in new habitats. However, this framework may inform studies of community response to environmental changes such as invasive species or habitat destruction.Item Scale and process : primate and non-primate mammal community composition and diversity in Madagascar(2015-05) Bannar-Martin, Katherine Hilary; Lewis, Rebecca J., 1972-; Leibold, Mathew A; Reed, Denne N; Di Fiore, Anthony; Hopkins, Mariah EThe study of community assembly, or the processes that shape the occurrence of species in an ecological community, is a fundamental area of inquiry in ecology. Patterns in community composition and diversity are attributed to the combined operation of deterministic (e.g., environmental sorting), stochastic (e.g., dispersal limitation), and biogeographic (e.g., dispersal barriers) processes. Environmental sorting results in communities composed of species that are ecologically adapted to their environment. Dispersal limitation results in communities shaped by the dispersal distance between sites. Biogeographic dispersal barriers prevent species dispersal between sites, and community membership is dependent upon site isolation. Community assembly is also dependent upon diversity type (taxonomic, functional, or phylogenetic) and spatial scale. I investigated the processes shaping the diversity of primate and nonvolant mammal communities using taxonomic, functional and phylogenetic diversity measures and a spatially explicit modelling approach. I described mammal diversity patterns at ecoregional, regional, and inter-regional scales within and across Madagascar and Australia. I tested the relationship of mammal community diversity to environmental, spatial, and biogeographic variables, indicating deterministic, stochastic, and biogeographic processes, in Madagascar and Australia. First, I found that arboreal mammal communities in Madagascar were more dispersal-limited than terrestrial mammal communities. Second, a combination of environmental sorting and dispersal limitation best explained primate taxonomic and functional diversity. Third, I tested for convergent diversity and assembly patterns in Madagascar and Australia, due to similar biogeographic and evolutionary histories, and found non-convergent patterns. Overall, biogeographic dispersal barriers were weak predictors of mammal diversity in Madagascar and Australia. Phylogenetic and functional diversity measures were weakly correlated, and phylogenetic diversity provided models with weak explanatory power. Environmental and spatial variables indicating the combined operation of environmental sorting and dispersal limitation variably shaped the taxonomic and functional diversity of mammal communities in Madagascar and Australia. Mammal community diversity was regionally specific, shaped by the unique historical and landscape components of each region, including ecoregional effects and the extinction of sympatric species. Macroscale studies of diversity should carefully investigate the influence of spatial scale and regional factors that can result in varied assembly patterns and unique ecological communities, such as those present for the nonvolant mammals of Madagascar and Australia.