Living on the edge: Plant diversity in the Iberian chionophilous vegetation

Abstract

Aims: Chionophilous vegetation (i.e. snowbed vegetation and chionophilous grasslands) hosts relict arctic-alpine species, among which snowbed specialists, that find their southernmost limit in the Iberian Peninsula, where they are especially threatened by climate change. Our aims were to identify the main Iberian chionophilous vegetation groups, and analyse their plant diversity patterns and their role as refugia for snowbed glacial relicts, as well as that of Iberian high-mountain regions. Location: Iberian high mountains. Methods: We used the beta-flexible clustering method to classify 1002 vegetation relevés of Iberian chionophilous vegetation, and computed species Indicator Values and frequencies for the resulting groups. We performed a Detrended Correspondence Analysis (DCA) ordination of the relevés, and fitted six climatic variables to reveal the main ecological gradients. We constructed rarefaction curves to compare species richness between vegetation groups and between mountain regions. Results: We obtained eight vegetation groups, four consisting of snowbed vegetation and four of chionophilous grasslands. All but one group were present in the Pyrenees, where snowbed specialist richness was the highest. In southern and central Iberian ranges, snowbed vegetation was extremely scarce, and the main vegetation group corresponded to cryoromediterranean grasslands, where both species and specialist richness were the lowest. Snowbed and northern Iberian grassland groups accounted for similar high specialist richness, although specialists were infrequent and scarce at relevé level in these grasslands. Conclusions: Despite the set of specialised species that thrive in snowbeds, many of them are also present but scarce in northern Iberian chionophilous grasslands. In a future scenario with a high reduction of snow cover duration, which may entail the disappearance of many snowbed vegetation patches, northern Iberian chionophilous grasslands may act as terminal refugia for snowbed specialists. Nevertheless, specialists are very threatened in central and southern Iberian ranges, where snowbed vegetation is infrequent and chionophilous grasslands provide almost no shelter to them.