Adaptive evolutionary divergence of populations persisting in warming cold-stage refugia: candidate examples from the periphery of the European Alps

The major response of organisms to the climatic oscillations of the Quaternary was migration. Considering alpine plants, migration into low elevation cold-stage refugia took place in glacial periods, and re-migration into high elevation areas in interglacial periods and the Holocene. The present review examines the possibility that populations at the rear edge of re-migrating species persisted and evolved in the area of cold-stage refugia. Here, they would be faced with increasingly warm conditions and strong competition from other species re-migrating into the cold-stage refugial area. For the flora of the European Alps, I identified 13 species or subspecies pairs in which one taxon of a pair may represent an evolutionary derivative of persisting rear-edge populations, whereas the other represents populations which tracked their niche and re-migrated into high elevation areas. If confirmed by further analyses, these taxon pairs would illustrate that adaptive evolutionary divergence in Quaternary interglacials and the Holocene is possible, and most likely can persist through one or several much longer glacial periods.