Local and regional community structure of sub-Arctic invertebrates

Background/Question/Methods

                The sub-Arctic site of Churchill, Manitoba, Canada is the subject of an ongoing All-Taxon Biodiversity Inventory employing DNA barcoding methods. With a nearly comprehensive barcode reference library now constructed for some taxonomic groups, this effort is enabling unique research into northern biodiversity, community structure, and climate change effects. We are using this reference library to explore two classical questions in ecology: what species live together and how do they coexist? Employing traditional and phylogenetic statistical methods, we are undertaking a research program to analyze community structure of invertebrates in different taxonomic groups, trophic levels, and spatial scales. Two projects at different scales are presented here.

                Firstly, we examine patterns of relatedness in highly local-scale communities within Churchill's freshwater habitats, which include rock bluff pools, tundra ponds, creeks, rivers, and lakes. DNA barcodes are first used to verify the identities of the larval and adult specimens encountered and, in combination with other markers, to construct phylogenetic relationships in Trichoptera (caddisflies) and other insects. Communities are investigated using classical coexistence statistics as well as phylogenetic community structure analysis, in which the phylogenetic diversities of local communities are compared with those of randomized communities generated from the regional species pool. Secondly, we conduct a regional-scale analysis of phylogenetic relatedness and compare patterns of genetic divergence and phylogenetic diversity across taxonomic groups of different diversity and trophic level.

Results/Conclusions

                Preliminary results from the first project indicate that some of Churchill's caddisfly communities display significant phylogenetic clustering, suggestive of community structuring via environmental filtering rather than competitive exclusion of close relatives. Ongoing steps are: to increase the sample size, conduct phenotypic analysis, incorporate information about cohabiting predator communities, and compare community structure at Churchill with other well-studied sites at different latitudes. Emerging results from the regional community analysis are discussed. This research provides novel insights into both the diversity and community structure of the sub-Arctic.