Disentangling the environmental and historical biogeography effects in island species distributions: A metacommunity phylogenetics approach

Background/Question/Methods

Species distributions in metacommunities are (at least partly) determined by the combination and interaction of biogeographical, evolutionary and ecological processes. Very few quantitative methods have been developed to quantify the effects and interactions of these processes on large-scale metacommunity assembly. Most methods developed for the study of community assembly either have focused on determining the role of one or very few potential (usually ecological) processes involved in community assembly, or have restricted their analyses to relatively small spatial scales. Typically, this kind of approach assumes that all sites share a common species pool of potential colonizers. Furthermore, although statistical approaches that integrate historical biogeography and phylogeny are becoming more common, our ability to detect and differentiate the roles of different metacommunity assembly processes (such as environmental filtering, biogeographical history, and dispersal limitation) has been particularly challenging.

Results/Conclusions
Here we use a recently developed method to determine the interaction between phylogenetic structure, historical biogeographic events and environmental filtering in driving species distributions in the insular metacommunity of Galapagos endemic land snails. We developed a novel approach to test for historical biogeographical events in the context of geological formation of islands and find that these geological events have strongly constrained the distribution of land snail species on these islands. Furthermore, we find that adaptation to different vegetation zones is also determinant in the metacommunity structure of this group of species. Our findings show that community structure on these islands results from a combination of biogeographic history and metacommunity processes such as dispersal. We argue that life histories of organisms such as dispersal ability might dictate the relative importance of these processes in determining species distributions in large-scale metacommunities.