High genetic differentiation in populations of the rare alpine plant species Campanula thyrsoides on a small mountain

Abstract

Changes in climate and traditional land use have contributed to a loss and fragmentation of suitable habitats for many alpine plant species. Despite the importance of these changes, our knowledge of the consequences for gene flow and genetic diversity is still poor, especially in rare taxa and at fine spatial scales. Here, we investigated the genetic diversity in a rare alpine plant on a small and highly structured mountain in the Swiss Alps. Using microsatellite markers and Bayesian cluster analyses, we investigated genetic diversity within and among 24 populations of Campanula thyrsoides L. We also tested whether landscape structure has affected genetic structure by correlating genetic diversity with landscape and population features, which were assessed in a four-year monitoring period. The recorded genetic diversity (H e = 0.714) and genetic differentiation (G 0 ST = 0.32) at distances of 1-10 km were remarkably high. Clustering analyses revealed a split of populations into two genetically different spatial groups, but between-population genetic distances were neither correlated to geographic distance, elevation nor slope. The high differentiation and genetic bottlenecks may indicate strong founder effects, although the number of alleles was not decreased in bottlenecked populations. We conclude that stochastic colonisation by seeds is most important for shaping the genetic structure of C. thyrsoides on this small mountain. The high genetic diversity even in small populations may indicate that occasional gene flow is strong enough to overcome negative effects of bottlenecks. Nevertheless, further fragmentation and isolation of habitats may threaten this rare plant in the future.

Two closely related species differ in their regional genetic differentiation despite admixing

“…Higher diversity in highland populations, as in our study in C. flava , was found in some studies, e.g. for Cystopteris fragilis (Pteridophyta) using isozymes (Gämperle and Schneller 2002), for Primula farinosa (Primulaceae) using RAPD analysis (Reisch et al 2005) and for Campanula thyrsoides (Campanulaceae) (Frei et al 2012), and was suggested to be due to higher mutation rates due to elevated radiation (Li et al 1997). However, others reported higher diversity of lowland populations, as we found for C. viridula (e.g.…”

Glacial History Affected Phenotypic Differentiation in the Alpine Plant, Campanula thyrsoides

“…Their remarkable population differentiation in various traits indicates that even at small spatial scales, populations may be substantially differentiated, either as the result of genetic drift or as an adaptation to their local environments. However, such differentiation is only possible when gene flow is restricted, as has recently been found for populations from this particular area [40], [41] (but see [42]). …”

“…Due to the current, strong isolation of C. thyrsoides populations in a heterogeneous environment and limited seed and insect-mediated pollen dispersal [40], [41], gene flow between populations since postglacial recolonisation is probably weak though not absent [12], [42]. This may have prevented homogenisation of phenotypic differentiation across populations from the phylogeographic regions, although considerable genetic introgression may be present between populations from the CSA and CAA regions (Fig.…”

A range‐wide genetic bottleneck overwhelms contemporary landscape factors and local abundance in shaping genetic patterns of an alpine butterfly (Lepidoptera: Pieridae: Colias behrii)

“…Are genetic bottlenecks unusual for alpine species? A number of studies (Paun et al 2008;Muster et al 2009;Frei et al 2011;Shama et al 2011) have recently shown that demographic history plays a larger role in shaping current patterns of genetic differentiation in alpine species and that the influence of large and ⁄ or recent population size changes may not be uncommon.…”