Biogeographic deconstruction of alpine plant communities along altitudinal and topographic gradients

QuestionsAre species from different biogeographic groups (mediterranean, alpine and endemic) filtered in different ways by altitude and topography in alpine plant communities? What is the relative performance of these environmental factors at predicting the species diversity of the communities as a whole and of the geographic species groups?LocationPicos de Europa, Cantabrian Range (Spain).MethodsWe sampled the presence and cover of vascular plants in 5-m radius plots on alpine grasslands between 1900 and 2500m a.s.l. Five GIS-based terrain variables at 15mx15m were used to model species richness and cover per plot using generalized and linear models, and the variation in species composition with redundancy analysis. The same analyses were repeated for the whole data set and for subsets of species from alpine, mediterranean and endemic distributions.ResultsThe influence of altitude and topography on species richness, cover and composition differed for the whole data set and for the geographic species groups. Altitude was the main variable affecting floristic diversity in the communities as a whole, but the separate species groups were more influenced by slope, topographic wetness index and solar radiation. Richness and cover of mediterranean species showed the strongest relationships with topography. Alpine and endemic species showed relationships with topography for species cover and composition, but not for species richness.ConclusionsIn alpine landscapes, biogeographic deconstruction of the species pool can provide a better understanding of the influence of altitude and topography on local communities than analysis of the entire community alone. Furthermore, the strong influence of local topography on species groups improves our understanding of how alpine species will respond to climate change.