Multilocus dataset reveals demographic histories of two peat mosses in Europe

Abstract

Background: Revealing the past and present demographic history of populations is of high importance to evaluate the conservation status of species. Demographic data can be obtained by direct monitoring or by analysing data of historical and recent collections. Although these methods provide the most detailed information they are very time consuming. Another alternative way is to make use of the information accumulated in the species' DNA over its history. Recent development of the coalescent theory makes it possible to reconstruct the demographic history of species using nucleotide polymorphism data. To separate the effect of natural selection and demography, multilocus analysis is needed because these two forces can produce similar patterns of polymorphisms. In this study we investigated the amount and pattern of sequence variability of a Europe wide sample set of two peat moss species (Sphagnum fimbriatum and S. squarrosum) with similar distributions and mating systems but presumably contrasting historical demographies using 3 regions of the nuclear genome (appr. 3000 bps). We aimed to draw inferences concerning demographic, and phylogeographic histories of the species.

20,000 species and five key markers: The status of molecular bryophyte phylogenetics

“…The large majority of publically available nuclear sequence data from byrophytes is attributable to Sphagnum, from ITS, 26S, gpd, LFY, and three anonymous nuclear loci (rapdA, rapdB, rapdF) (e.g. Shaw et al 2003;Szövényi et al 2007;Shaw et al 2008b). The anonymous loci are not further discussed here.…”

“…Of these, GapC in part, (referred to as gpd) was first used in plant phylogenetics by Martin et al (1993), and for the first time employed in bryophytes by Wall (2002Wall ( , 2005 in Mitthyridium. Later, this marker was also used for the Calymperaceae in general (Fisher et al 2007) and in Sphagnum (Szövényi et al 2007). GapC was chosen because it is easy to amplify and single-copy in bryophytes (cf.…”

Glacial refugia and post-glacial colonization patterns in European bryophytes

“…However, the clusters are only weakly structured in Europe, possibly due to extensive gene flow. Sphagnum fimbriatum Wilson on the other hand, is found to be highly structured in one 'Atlantic' and one 'non-Atlantic' clade (Szövenyi et al 2006(Szövenyi et al , 2007. The Atlantic clade likely survived the LGM along the western coast and is currently found from southern England to northern Spain, while the non-Atlantic clade is widespread in Europe and probably recolonized the continent rather rapidly after the LGM.…”

“…Several refugia have been hypothesized for Sphagnum squarrosum Crome, and three genetic clusters are found in this species (Szövenyi et al 2006(Szövenyi et al , 2007. However, the clusters are only weakly structured in Europe, possibly due to extensive gene flow.…”

“…The Atlantic clade likely survived the LGM along the western coast and is currently found from southern England to northern Spain, while the non-Atlantic clade is widespread in Europe and probably recolonized the continent rather rapidly after the LGM. This discrepancy between lineage distributions could be explained by the widespread clade being able to fill niches becoming available after the ice retreated, while the Atlantic clade possibly was unable to do the same, and hence became restricted to the southwestern coast of Europe (Szövenyi et al 2007). …”