Abstract
Recent evidence suggests that survival of arctic-alpine organisms in peripheral or interior glacial refugia are not mutually exclusive and may both be involved in shaping an organism’s Pleistocene history, yet potentially at different time levels. Here, we test this hypothesis in a high-mountain plant (diploid lineage of Senecio carniolicus, Asteraceae) from the Eastern European Alps, in which patterns of morphological variation and current habitat requirements suggest survival in both types of refugia. To this end, we used AFLPs, nuclear and plastid DNA sequences and analysed them, among others, within a graph theoretic framework and using novel Bayesian methods of phylogeographic inference. On the basis of patterns of genetic diversity, occurrence of rare markers, distribution of distinct genetic lineages and patterns of range connectivity both interior refugia in the formerly strongly glaciated central Alps and peripheral refugia along the southern margin of the Alps were identified. The presence of refugia congruently inferred by markers resolving at different time levels suggests that these refugia acted as such throughout several glacial cycles. The high degree of range persistence together with gradual range expansion, which contrasts with the extent of range shifts implied for other Alpine species, is likely responsible for incipient lineage differentiation evident from the genetic data. Replacing a simplistic peripheral vs. interior refugia dualism by more complex models involving both types of refugia and considering different time levels will help identifying common phylogeographic patterns with respect to, for instance, location of refugia and colonization routes and elucidating their underlying genetic and/or ecological causes.
Highlights
A central question of arctic-alpine phylogeography is concerned with Pleistocene range dynamics and the location of refugial areas
Often confrontational assertions, glacial survival in peripheral refugia does not preclude survival in interior refugia, and both may contribute to shaping Pleistocene range dynamics of alpine biota (Stehlik et al 2002; Lohse et al 2011)
This is the case for diploid Senecio carniolicus, where several peripheral and interior refugia have been identified based on increased frequency of rare AFLP markers (Fig. 1b), elevated haplotype diversity and the distribution patterns of the oldest and most divergent haplotype lineages (Fig. 2)
Summary
A central question of arctic-alpine phylogeography is concerned with Pleistocene range dynamics and the location of refugial areas Convincing evidence for nunatak survival in central parts of the Alps is much scarcer (Stehlik et al 2002; Bettin et al 2007; Parisod & Besnard 2007). Additional aspects of interest include, for instance, connectivity among different refugial areas or modes and directions of range expansions Such aspects may be tested using statistical phylogeographic approaches (Knowles & Maddison 2002; Knowles 2009), the sheer amount of plausible hypotheses that often need to be considered renders their application unfeasible except for simple settings Nunatak survival has already been suggested for S. halleri (Bettin et al 2007), a closely related endemic of the Western Alps with similar habitat requirements
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