Gradual decline in genetic diversity in Swiss stone pine populations (Pinus cembra) across Switzerland suggests postglacial re-colonization into the Alps from a common eastern glacial refugium

Abstract

Molecular genetic markers may reveal informative patterns of population processes such as historical migration, which may substantiate inference on postglacial re-colonization inferred, e.g., from fossil records. Palynological records of Swiss stone pine (Pinus cembra) suggest that the species has re-colonized the central Alps from a southeastern Alpine refugium after the last glacial maximum. Such a migration pathway likely resulted in a gradual decrease in genetic diversity with increasing distance to the glacial refugium, owing to founder events at the leading range edge. The present distribution of P. cembra in Switzerland consists of two rather distinct ranges, namely the inner-alpine parts of the Grisons and Valais, respectively, and additional disjunct occurrences in the northern and southern periphery of the Alps as well as between the two main ranges. We screened chloroplast microsatellite loci on 39 Swiss P. cembra populations and show that the genetic structure detected was congruent with a common ancestry from a single glacial refugium, likely located at the (south-)eastern periphery of the Alps. In contrast, our data rejected the alternative hypothesis of a distinct genetic separation of the two main ranges of Swiss stone pine in Switzerland. We further show that low genetic diversity within and high differentiation among peripheral populations in the northern Alps as well as the genetic differentiation between core and peripheral populations reflect genetic drift as a consequence of colonization history and limited gene flow by pollen and seed.

No reduction in genetic diversity of Swiss stone pine (Pinus cembra L.) in Tatra Mountains despite high fragmentation and small population size

“…3). Overall, the pattern of genetic differentiation of Swiss stone pine is rather shallow (Belokon et al 2005;Gugerli et al 2001Gugerli et al , 2009Höhn et al 2009), indicating recent fragmentation of a common gene pool that formerly occupied a larger range. …”

“…Such structure may be a result of spatial isolation hampering gene flow among fragmented populations. In the Alps, Gugerli et al (2009) found a gradual decline of chloroplast DNA diversity from East to West, along the colonization route from a single glacial refugium located at the (south-) eastern periphery of the Alps. This pattern is in accordance with the ''abundant center model'' and reflects the process of genetic drift through founder events and/or bottlenecks, coupled with reduced gene flow related to postglacial colonization dynamics.…”

Development and transferability of two multiplexes nSSR in Scots pine (Pinus sylvestris L.)

“…In conifers, nSSRs are applied in multiple research areas such as population studies (e.g., Marshall et al 2002;A 0 Hara and Cottrell 2004;Waldmann et al 2005;García-Gil et al 2009;Gugerli et al 2009;Tollefsrud et al 2009), genetic map construction (Pelgas et al 2006;Echt et al 2011) and paternity analysis (Lian et al 2001;Torimaru et al 2009). Despite the wide application of nSSRs, examples on the application of SSR multiplexing in conifers remain scarce (Devey et al 2002;Bell et al 2004;Karhu et al 2006;Gugerli et al 2009;Salzer et al 2009;Kawase et al 2010;Wagner et al 2012).…”

Current range characteristics of Swiss stone pine (Pinus cembraL.) along the Carpathians revealed by chloroplast SSR markers

“…postglacial range formations are mainly affected by the recolonization routes. it is also largely accepted that founder events towards the edge of a species' range cause the gradual decrease of the population genetic diversity [17,6]. finally, the genetic parameters of the existing populations are determined by biogeographical characteristics, gene flow and effective populations size [3,13].…”