Altitudinal species richness patterns of vascular plants in the south-eastern Pyrenees and nearby mountains of Catalonia

Abstract

Background: Studying how species richness varies with altitude has become an important part of investigations on mechanisms explaining regional-scale plant species diversity. Altitudinal diversity patterns are poorly known in the Pyrenees and elsewhere in the main mountain massifs in Catalonia (north-eastern Iberian Peninsula). Aim: We examine the altitudinal patterns of species richness in the Catalan Pyrenees and compare them with those in other mountains in Catalonia. Altitude patterns of species richness in the Pyrenees are compared for functional and taxonomic groups of vascular plants. Methods: Data on vascular plants were obtained from the Biodiversity Data Bank of Catalonia. We used rarefaction and interpolation to quantify the altitudinal diversity patterns. Results: The interpolated and rarefied richness generally peaked in the lower part of the altitudinal gradient, but with remarkable variation depending on the taxonomic or functional groups considered. Using all species, there was little variation between the different mountains, but the altitude at which richness started to decrease varied between them. Conclusions: The pronounced differences among different taxonomic groups and life-forms indicate a strong phylogenetic and adaptive signal on the altitudinal diversity pattern in the Catalan Pyrenees. The lack of regional differences within Catalonia is probably due to small differences in the intensity of climatic gradients across mountains.