Pleistocene glacial cycles as drivers of allopatric differentiation in Arctic shorebirds

AIM: Spatio‐temporal changes have likely caused range fragmentation and population isolation, which could have given rise to the observed current intraspecific differentiation in some species. Here, we test several hypotheses on the potential effect of Pleistocene glacial cycles in the diversification of Arctic shorebird species, comparing between different scenarios of fragmentation of the breeding distribution during glacial and interglacial periods. LOCATION: Global. TAXON: Arctic migratory shorebirds. METHODS: We performed species distribution models (SDMs) to explore the changes in the breeding and non‐breeding ranges of 69 species between the last glacial maximum (c. 21,000 years ago) and the present. We also included independent evidence from the fossil record and estimations on the potential extension of the tundra during glacial periods to validate the results from the SDMs. We assigned each species to one of four potential scenarios based on fragmentation and potential recolonization patterns of their breeding ranges during glaciations. RESULTS: Our findings show that most of the species with subspecies experienced fragmentation of their ranges during the glacial, the interglacial or both periods. Meanwhile, the majority of the monotypic species maintained their ranges as a continuum. Moreover, the impacts of glacial cycles in the distribution were not homogeneous across the Arctic, and some regions were more prone to the fragmentation of breeding ranges than others. MAIN CONCLUSIONS: Our work suggests that Pleistocene climatic cycles drove the diversification of Arctic shorebirds by creating allopatric breeding distributions. While the fragmentation of the breeding ranges occurred mainly during glacial periods, interglacials also played a part in maintaining or establishing newly isolated breeding populations for many species. Furthermore, species' distribution changes varied between different regions and habitats, which determined current shorebird diversity patterns.