Glacial refugia and post-glacial colonization patterns in European bryophytes

Most species are assumed to have survived south or east of the ice sheet covering northern Europe during the last glacial maximum. Molecular and macrofossil evidence suggests, however, that some species may have survived in ice-free areas in Scandinavia. In plants, inbreeding and vegetative growth are associated with low genetic load and enhanced survival in small, isolated populations. These characteristics are often found in bryophytes, possibly allowing them to survive extreme conditions in isolated refugia and also within ice sheets. Here, we review the Holocene bryophyte history in Europe highlighting main glacial refugia and post-glacial colonization routes. Also, meta-analyses are performed to investigate if distribution ranges and genetic structure are associated with life-history traits. Bryophytes survived the last glaciation in several refugia, but there is no unequivocal evidence of survival within the Scandinavian ice sheet. Northern Europe was colonized from southern, eastern and western Europe, as well as North America. Species with small spores have broader distribution ranges than species with large spores, and high frequency of sporophyte production is associated with limited genetic differentiation between populations.