The uneven distribution of refugial endemics across the European Alps suggests a threefold role of climate in speciation of refugial populations

Abstract

A little more than 10% of the vascular plant flora native to the European Alps is endemic to this area. It has long been noticed that the distribution of endemics across the Alps is very uneven. While most endemics are found along the southern edge of the Alps, with some also on its western, eastern, and northeastern edges, the northern edge of the Alps more or less between Lake Geneva in the west and Lake Traun in the east harbours almost no endemics. The distribution of endemics in the Alps has often been related to the location of glacial refugia. Accordingly, the virtual absence of endemics from the northern edge of the Alps has been explained with the unsuitability of climatic conditions for glacial survival of alpine plants there. After discussing evidence for the existence of glacial refugia for alpine species along the northern edge of the Alps and north of the Alps, I will examine how these refugia differed from refugia along the southern edge of the Alps. I conclude that the uneven distribution of endemics in the Alps is best explained by the different climate through time north and south of the Alps. These climatic differences affected the spatial structure and extent of refugia, the length of isolation of refugial populations, and selective conditions in refugia.