The role of competition in driving species global distributions: Soricid shrews as a case study

摘要

Aim 6We aim to determine the relative influence of climate and species interactions on the global distribution of Soricinae and Crocidurinae shrews through the analysis of their distribution, climate niche and evolutionary history. Both subfamilies are partially allopatric in Eurasia, but in North America only Soricinae is present, thus providing a scenario to address the role of potential competition versus competitive release in determining species' realized distributions at a global scale. Location Global. Taxon Soricidae, Eulipotyphla. Methods We obtained climate data from WorldClim, spatial range data for 302 species from the IUCN Red List and 2614 cytb complete sequences from GenBank. We modelled the potential distribution of the subfamilies by computing three environmental niche models using Maxent: one for Crocidurinae, one for American Soricinae and one for Afro-Eurasian Soricinae. We created matrices for the genetic, spatial and climatic distance between all pairs of species to calculate the average climatic distance between pairs of species within and between subfamilies. We then evaluated this distance against a null model. To assess the effect of phylogeny on the segregation of the subfamilies, we checked for correlation between genetic and spatial distance. Results The Afro-Eurasian Soricinae environmental niche model under-predicted its occurrence in America. The average climatic distance between subfamilies was larger than expected by chance, while the distance within both Crocidurinae and Afro-Eurasian Soricinae was smaller. The average distance between the American and Afro-Eurasian Soricinae was also larger than expected. There was no correlation between spatial and genetic distance for genetic distances over 0.14 substitutions per nucleotide site. Main conclusions Climate significantly influences the distribution of both subfamilies. As expected in a scenario of competitive release, the climatic range of the Soricinae in America is larger than in Afro-Eurasia. Thus, besides climate, competition may play an important role in shaping species' global distributions.