Demographic response of alpine biota to climate change

One way to better understand how species occurring at high elevations in the Alps respond to the current climate change is to investigate how these species have responded to past climate changes. In the context of climate oscillations during the Pleistocene and Holocene, two hypotheses have been proposed: (i) The postglacial contraction hypothesis suggests that during cold periods, species survived in the ice-free periphery of mountain ranges and in adjacent lowland regions, resulting in range expansion, whereas in the warmer postglacial period, these species retreated to high-elevation refugia, thus decreasing their range sizes. (ii) The postglacial expansion hypothesis proposes that during cold periods high-elevation species were restricted to small refugia, resulting in range contraction, whereas in the postglacial period, these species expanded into formerly glaciated areas thus expanding their ranges. It can be expected that the response of species to climate change also depends on habitat preference, but this has not been tested in a comparative manner. Therefore, it remains unclear whether Pleistocene range dynamics of high- elevation species are in line with the postglacial contraction or the postglacial expansion hypothesis and whether adherence to one or the other hypothesis is associated with ecological features of the species. Using genome-wide molecular data for 20 plant and 10 animal species, we will address the following questions: Did high-elevation species of the Alps respond to Pleistocene climate oscillations by postglacial expansion or by postglacial contraction? Were these range shifts affected by the ecological characteristics of these species? Are past population size and range changes predictive of changes expected under current global climate change? By comparatively studying species from different plant and animal lineages, it will be possible to distinguish (i) general patterns (i.e., applicable to many species) from idiosyncratic ones (i.e., applicable to single or a few species only) and (ii) patterns specific to certain major groups (e.g., animals vs. plants) to be discerned from patterns specific to certain ecological groups (e.g., species from swards vs. screes). By identifying characteristics affecting the response of high-mountain species to global warming in a predictable manner, the proposed research can significantly contribute towards generating hypotheses with respect to the fate of high-elevation species under current global climate change.