Mountain biota survived the Quaternary cold stages in peripheral refugia and/or ice-free peaks within ice-sheets (nunataks). While survival in peripheral refugia has been broadly demonstrated, evidence for nunatak refugia is still scarce. We generated RADseq data from three mountain plant species occurring at different elevations in the southeastern European Alps to investigate the role of different glacial refugia during the Last Glacial Maximum (LGM). We tested the following hypotheses. (i) The deep Piave Valley forms the deepest genetic split in the species distributed across it, delimiting two peripheral refugia. (ii) The montane to alpine species Campanula morettiana and Primula tyrolensis survived the LGM 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 LGM. By contrast, the higher-elevation species shows long-term stability of population sizes due to survival on permanently ice-free peaks and small population sizes at present. 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 montane to alpine C. morettiana. Altitudinal segregation influenced the species’ demographic fluctuations, with the lower-elevation species showing a significant population increase at the end of the LGM, 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 nunatak survival and species ecology in the demographic history of mountain species.

A document by Francesco Rota. Click on the document to view its contents.

Aims: Habitat richness, i.e. the diversity of ecosystem types, is a complex, spatially explicit aspect of biodiversity, which is affected by bioclimatic, geographic and anthropogenic variables. The distribution of habitat types is a key component for understanding broad-scale biodiversity and for developing conservation strategies. To test which factors are related with habitat richness we used EU habitat distribution data to answer the following questions: i) how do bioclimatic, geographic, and anthropogenic variables affect habitat richness? ii) which category is the most important? iii) how do interactions among these variables influence habitat richness and which combinations produce the strongest interactions? Study area: European Union (excluding Greece) plus the United Kingdom. Methods: We used the distribution maps of 233 terrestrial habitat types defined by the European Environmental Agency, to calculate habitat richness for the EU 10 km x 10 km grid map. We then investigated how environmental variables affect habitat richness, using generalized linear models, generalized additive models and boosted regression trees. Results: The main factors associated with habitat richness were geographic variables, with negative relationships observed for both latitude and longitude, and a positive relationship for terrain ruggedness. Bioclimatic variables played a secondary role, with habitat richness increasing slightly with annual mean temperature and overall annual precipitation. An interaction between anthropogenic variables was important: the combination of increased landscape fragmentation and increased population density strongly decreased habitat richness. Main conclusions: This is the first attempt to disentangle spatial patterns of habitat richness at the continental scale, as a key tool for protecting biodiversity. The diversity of European habitats is correlated withgeography more than climate and human pressure, reflecting a major component of biogeographical patterns similar to the drivers observed at the species level. The interaction between anthropogenic variables highlights the need for coordinated, continental-scale management plans for biodiversity conservation.