Pleistocene climate change and the formation of regional species pools

This preprint has been reviewed and recommended by Peer Community In Evolutionary Biology ( https://doi.org/10.24072/pci.evolbiol.100053 ). Despite the description of bioregions dates back from the origin of biogeography, the processes originating their associated species pools have been seldom studied. Ancient historical events are thought to play a fundamental role in configuring bioregions, but the effects of more recent events on these regional biotas are largely unknown. We use a network approach to identify regional and sub-regional faunas of European Carabus beetles, and analyse the effects of dispersal barriers, niche similarities and phylogenetic history on their configuration. We identify a transition zone matching the limit of the ice sheets at Last Glacial Maximum. While southern species pools are mostly separated by dispersal barriers, in the north species are mainly sorted by their environmental niches. Strikingly, most phylogenetic structuration of Carabus faunas occurred during the Pleistocene. Our results show how extreme recent historical events –such as Pleistocene climate cooling, rather than just deep-time evolutionary processes, can profoundly modify the composition and structure of geographic species pools.