The role of in situ species diversification for the evolution of high vascular plant species diversity in the European Alps—A review and interpretation of phylogenetic studies of the endemic flora of the Alps

By harbouring ca. 3500 native vascular plant species in an area of ca. 170 000 km2, the European Alps represent a region of very high species diversity. Using the most recently published flora of the area and phylogenetic literature, I here review which proportion of the endemic flora of the Alps is the result of in situ diversification, i.e., of diversification in the area and (largely) restricted to the area. There exist only very few and mostly species-poor species diversifications in the Alps, accounting for ca. 1.2% of the native and for ca. 9% of the endemic flora of the Alps. In contrast to this, ca. 33% of the endemic species of the Alps belong to lineages widespread in the European Alpine System (EAS), comprising mainly the Pyrenees, Apennines, Carpathians, Dinarids and Balkans, in addition to the Alps. The rarity of Alpine species diversifications is hypothesised to reflect the Quaternary climatic history of the Alps where massive and repeated glaciations prevented the undisturbed evolution of species-rich lineages.