Glacial refugia and post-glacial colonization patterns in European bryophytes

Abstract

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, metaanalyses 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.

Phylogeography of Alpine populations of Rhytidium rugosum (Bryophyta) in a European context

“…Brochmann et al 2003;Hedenäs 2015;Hewitt 2000;Jaarola et al 1999;Kyrkjeeide et al 2014;Parducci et al 2012;Taberlet et al 1998). Several recent studies concerned plants, especially flowering plants, in the European Alps (from here on called 'the Alps') (e.g.…”

Future directions and priorities for Arctic bryophyte research

“…We also consider regions south of the tree line to 50°N (Fig. 2.) because many Arctic bryophyte taxa have ranges extending to sub-Arctic and boreal zones (Brassard 1971;Schofield 1971;Steere 1971Steere , 1978Longton 1988) and migration between lower latitudes and the Arctic is at least historically significant (Kyrkjeeide et al 2014). Additionally, bryophyte communities influence seedling environments (e.g., Soudzilovskaia et al 2011), while trees alter the microclimate in which bryophytes grow (Longton 1988), making the tree line an ecologically relevant feature for delimitation.…”

“…Given the limited literature on Arctic bryophytes at the circum-Arctic scale and employing molecular data, comparisons and inferences based on other land plant lineages are included to illuminate gaps and hypotheses that may guide studies on Arctic bryophyte phylogeography and diversity. We aim to complement a number of comprehensive reviews published over the past 5 years regarding the resilience and functional roles of Arctic and boreal bryophytes (Turetsky et al 2012), the phylogeographic history of the European Quaternary bryoflora (Kyrkjeeide et al 2014), the biogeography of polar photoautotrophs (Pointing et al 2015), the Sphagnum microbiome (Kostka et al 2016), and the physiological responses of bryophytes to increasing temperatures (He et al 2016). We discuss the utility of museum collections, providing a brief discussion of digitally accessible specimen data, in conjunction with molecular data to understand how species richness, based on morphological species concepts, reflects genetic diversity.…”

“…3. for extent and retreat of the Laurentide ice sheet) (Dickson 1973 and references therein; Shafer et al 2010; see Kyrkjeeide et al 2014 for discussion on the Scandinavian ice sheet), with strictly circumArctic species possibly representing remnants of a widely distributed Tertiary or interglacial flora that only survived in northern refugia. This hypothesis was recently tested using molecular data in a phylogenetic context for the moss Bryoxiphium norvegicum and was rejected ).…”

“…However, our current knowledge of floristic and genetic diversity, evolutionary history, and dispersal in the Arctic is sparse for these ecologically significant plants (but see Piñeiro et al 2012;Kyrkjeeide et al 2014Kyrkjeeide et al , 2016aKyrkjeeide et al , 2016b. This is an increasingly conspicuous and important knowledge gap in the face of rapid climate change in the polar regions (Urban et al 2016).…”