No borders during the post-glacial assembly of European bryophytes

Climatic fluctuations during the Last Glacial Maximum (LGM) exerted a profound influence on biodiversity patterns, but their impact on bryophytes, the second most diverse group of land plants, has been poorly documented. Approximate Bayesian computations based on coalescent simulations showed that the post-glacial assembly of European bryophytes involves a complex history from multiple sources. The contribution of allochthonous migrants was 95–100% of expanding populations in about half of the 15 investigated species, which is consistent with the globally balanced genetic diversities and extremely low divergence observed among biogeographical regions. Such a substantial contribution of allochthonous migrants in the post-glacial assembly of Europe is unparalleled in other plants and animals. The limited role of northern micro-refugia, which was unexpected based on bryophyte life-history traits, and of southern refugia, is consistent with recent palaeontological evidence that LGM climates in Eurasia were much colder and drier than what palaeoclimatic models predict.AL, AD, BL and AV acknowledge financial support from the Belgian Funds for Scientific Research (F.R.S.-FNRS). J.P. was funded by the Spanish ‘Ministerio de Economía y Competitividad’ through the Juan de la Cierva Program–Incorporation(IJCI-2014-19691) and Ramón y Cajal Program (RYC-2016-20506), and Marie Sklodowska-Curie COFUND, Researchers’Night and Individual Fellowships Global (grant 747238). BL and AD acknowledge financial support from SYNTHESYS (ES-TAF, GB-TAF, NL-TAF) and WBI (Wallonie Bruxelles International). SFM was supported by funds from the University of Florida. Computational resources were provided by theConsortium desEquipements de Calcul Intensif funded by F.R.S.-FNRS (Grant 2.5020.11).Peer Reviewe