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Altitudinal segregation partially predicts survival of three alpine plant species across nunatak and peripheral glacial refugia
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  • Francesco Rota,
  • Pau Carnicero Campmany,
  • Gabriele Casazza,
  • Juri Nascimbene,
  • Peter Schönswetter,
  • Camilla Wellstein
Francesco Rota
Free University of Bozen-Bolzano
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Pau Carnicero Campmany
University of Innsbruck

Corresponding Author:[email protected]

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Gabriele Casazza
University of Genoa
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Juri Nascimbene
University of Bologna
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Peter Schönswetter
University of Innsbruck
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Camilla Wellstein
Free University of Bozen-Bolzano
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Abstract

Survival of Quaternary cold stages in peripheral refugia and/or ice-free peaks within ice-sheets (nunataks) has likely (co)shaped the genetic structure of temperate mountain biota. We used three altitudinally segregated species endemic to the Dolomites and the adjacent Carnic Prealps in the southeastern European Alps to perform genetic structure analyses and demographic modeling based on RADseq data and retrospective species distribution models to test the following hypotheses. (i) The deep Piave valley forms the deepest genetic split in the species distributed across it. (ii) The montane to alpine species Campanula morettiana and Primula tyrolensis survived the Quaternary cold stages in peripheral refugia, while high-alpine to subnival Saxifraga facchinii likely survived in several nunatak refugia. (iii) The lower-elevation species suffered a strong population decline during the Quaternary glaciation. By contrast, the higher-elevation species shows long-term stability of population sizes due to survival on permanently ice-free peaks. We found peripheral refugia on both sides of the Piave Valley, which acted as a major genetic barrier. Demographic modeling confirmed nunatak survival not only for S. facchinii, but also for C. morettiana; results were inconclusive for P. tyrolensis. Altitudinal segregation influenced the species’ demographic fluctuations, with the lower-elevation species showing a significant population increase at the end of the Quaternary cold stages, and the higher-elevation species either showing decrease towards the present or stable population sizes with a short bottleneck. Our results highlight the role of both nunatak survival and of species ecology in the demographic history of mountain species.