GLACIAL SPECIALIST SPECIES ARE MORE VULNERABLE TO CLIMATE CHANGE THAN GENERALIST SPECIES (DRAWING PARELLELS BETWEEN EMPIRICAL AND ECOLOGICAL DISTINCTIONS)

Abstract

In Switzerland, glaciers are projected to shrink to minimal size by the end of the century. Thus, climate change puts pressure on glacial specialist plant species, as generalist plant species colonise their habitat. As bare areas are revealed by glacier retreat, glacial specialists can likewise shift their distributions to higher altitude, however, there will be no habitat for them to colonise. Thus, Swiss mountain floral biodiversity and ecosystem services will likely be locally extirpated. In this article, we use Species Distribution Models of 369 plants occurring in Swiss proglacial areas fitted using bioclimatic, lithological and topographic variables and compare the covariates that most strongly predict the distributions of glacial specialist and generalist species. In addition, we use two methods of defining glacial specialist species and separating them from specialists: empirical (degree of prevalence of species in proglacial areas) and ecological (using Landolt values). We find that both approaches yield similar results: the distributions of both generalist and glacial specialist species are most strongly predicted by bioclimatic variables, however, they are significantly stronger for glacial specialists. On the other hand, distributions of generalist species are more strongly predicted by topographical and lithological variables.