An explicit test of Pleistocene survival in peripheral versus nunatak refugia in two high mountain plant species.

Da Pan,Gerald M Schneeweiss,Wolfgang Willner,Karl Hülber

doi:10.1111/mec.15316

Abstract

Pleistocene climate fluctuations had profound influence on the biogeographical history of many biota. As large areas in high mountain ranges were covered by glaciers, biota were forced either to peripheral refugia (and possibly beyond to lowland refugia) or to interior refugia (nunataks). However, nunatak survival remains controversial as it relies solely on correlative genetic evidence. Here, we test hypotheses of glacial survival using two high alpine plant species (the insect‐pollinated Pedicularis asplenifolia and wind‐pollinated Carex fuliginosa) in the European Alps. Employing the iDDC (integrative Distributional, Demographic and Coalescent) approach, which couples species distribution modelling, spatial and temporal demographic simulation and Approximate Bayesian Computation, we explicitly test three hypotheses of glacial survival: (a) peripheral survival only, (b) nunatak survival only and (c) peripheral plus nunatak survival. In P. asplenifolia the peripheral plus nunatak survival hypothesis was supported by Bayes factors (BF> 100), whereas in C. fuliginosa the peripheral survival only hypothesis, although best supported, could not be unambiguously distinguished from the peripheral plus nunatak survival hypothesis (BF = 5.58). These results are consistent with current habitat preferences (P. asplenifolia extends to higher elevations) and the potential for genetic swamping (i.e., replacement of local genotypes via hybridization with immigrating genotypes [expected to be higher in the wind‐pollinated C. fuliginosa]). Although the persistence of plants on nunataks during glacial periods has been debated and studied over decades, this is one of the first studies to explicitly test the hypothesis instead of solely using correlative evidence.

Highlights

Pleistocene climate fluctuations had profound influence on the biogeographical history of many biota (Hewitt, 1996, 2004)
In the case of mountain ranges, the focus of the present study, species might have retreated to unglaciated areas at their periphery and possibly beyond into lowlands, as supported by fossil data (Birks & Willis, 2008) and by molecular data (Comes & Kadereit, 1998; Cosacov, Sérsic, Sosa, Johnson, & Cocucci, 2010; Fulton, Norris, Graham, Semken, & Shapiro, 2013; Marr et al, 2008; Schönswetter et al, 2005; Stehlik, 2000; Tollefsrud, Bachmann, Jakobsen, & Brochmann, 1998) for many plant species
Their current distribution ranges encompass both areas situated in formerly glaciated regions, where they may have survived on nunataks, and areas outside the former ice-sheet, where they may have survived in peripheral refugia (Figure 2)

Summary

| INTRODUCTION

Glacial survival patterns of two plant species, Pedicularis asplenifolia and Carex fuliginosa, were investigated in the European Alps, a geographical model system to study Pleistocene range shifts (Escobar García et al, 2012; Lohse et al, 2011; Schönswetter et al, 2005). As species that can cope with cold harsh environments are likely to be able to survive in extreme habitats such as nunataks (Lohse et al, 2011; Stehlik et al, 2002), they are excellent candidates to test glacial survival hypotheses Their current distribution ranges encompass both areas situated in formerly glaciated regions, where they may have survived on nunataks, and areas outside the former ice-sheet, where they may have survived in peripheral refugia (Figure 2). Using RAD-seq (restriction site associated DNA sequencing) data analysed with the iDDC approach, we here test three glacial survival scenarios identified previously: peripheral survival only, nunatak survival only and peripheral plus nunatak survival (e.g., Escobar García et al, 2012; Schönswetter, Tribsch, Stehlik, & Niklfeld, 2004; Stehlik et al, 2002)

| MATERIALS AND METHODS

Findings

| DISCUSSION

| CONCLUSION