Closely related species tend to have similar traits and niches, and therefore when we examine a phylogeny, we can assess the degree of niche overlap of co-occurring species. Depending on the dominant factor influencing community assembly, different patterns can emerge in terms of the phylogenetic relatedness of co-occurring species. Our study aims to understand the phylogenetic co-occurrence patterns of sub-arctic freshwater marcoinvertebrates and how they vary over time and with environmental variation. To answer this question, we collected macroinvertebrates from 75 habitats three times throughout the summer of 2010 in Churchill, MB, Canada. We sequenced cytochrome c oxidase subunit I, RNA polymerase II, cadherin and elongation-factor 1α to construct a regional maximum likelihood phylogeny for Trichoptera (comprising 46 species). We determined the degree of relatedness between species co-existing in local-scale communities using the nearest taxon index (NTI), as well as analyzed habitat characteristics and water chemistry to understand the dominant variables influencing the observed phylogenetic patterns.
Results/Conclusions
Preliminary results indicate that Trichoptera in lotic habitats are composed of distantly related species, indicating a more prominent role of competition in structuring these communities. However, Trichoptera that co-occur in lentic habitats are closely related, suggesting environmentally assembled communities. Yet as the summer progresses, lentic communities shift to more distantly related species co-occurring, which implies a shift to a competitively assembled community. Considering the temporal shift in phylogenetic patterns observed in sub-arctic freshwater communities, as well as the variation seen between habitat types, future studies should aim to include these components to help us further develop our knowledge of community assembly.