Frontiers of Biogeography

Information on the paleo-beta diversity of fossil assemblages and its patterning in different geological time intervals helps us to better understand the community level response of biodiversity patterns to current global warming. We focused on the impact of paleoclimate changes on large-scale taxonomic sorting related to geography; specifically, how cooler and warmer climatic conditions affect the distance-dependency of beta diversity. Using a dataset of Cenozoic fossil assemblages of angiosperm woody plants (7,468 data points; 310 genera in 95 families) in the Japanese portion of the East Asian archipelago (except Ryukyu islands), we modeled the distance-dependency of genus turnover (pairwise compositional dissimilarity) through the Oligocene, Miocene, Pliocene, Pleistocene, Last Glacial Period, Holocene, and present day. The genus turnover of angiosperm woody plants was significantly correlated with geographical and climatic distance only in the Last Glacial Period, Holocene, and present day. During the Oligocene to Pliocene, the warm periods, genus turnover was mostly independent of geographical distance. Spatial/climatic distance-dependent turnover under colder environments involved a climate-induced sorting process to spatially diversify woody-plant assemblages across the archipelago. Moreover, the predominance of distant-independent turnover suggested the effect of dispersal release under warmer, stable climates. Our findings suggest that future tropicalization in temperate habitats could promote geographical homogenization of biodiversity patterns.