Vortrag (eingeladen), Island Biology 2016, Angra do Heroísmo, Terceira, Portugal: 18.07.2016 - 22.07.2016
Climate and topography are among the most fundamental drivers of plant diversity. High elevation islands offer a diverse setting of climatic and topographic conditions (so-called climatic mini-continents), enabling us to study the influence of both factors on spatial patterns of endemism. Islands in general, and high elevation island in particular, are famed for being excellent study objects of drivers of diversity and speciation processes. Therefore, we use the high elevation island of La Palma (Canary Islands) to test the relative importance of climate and topography on the spatial pattern of plant endemism using a large number of plots (n = 890) covering all major environmental gradients of the island. Surprisingly, the relative importance of climate strongly differs depending on which response variables we focus on, i.e. endemic richness (a measure of biodiversity) or speciation-related endemicity (percentage of endemics). Topography best predicts endemic richness, while climate is most important for endemicity. The hotspots of endemic richness in topographic complex and steep regions are likely a combined result of evolutionary processes (preadaptation to rupicolous conditions, micro-refugia, dispersal limitations) and human-induced influences (introduced herbivores, fire, land use). In contrast, the hotspots of endemicity at the highest elevations of the island are likely driven by specialization to local conditions and large-scale isolation effects (topography-driven isolation). The spatial incongruence in hotspots of endemic richness and endemicity emphasizes the need for an integrated conservation approach acknowledging different diversity measures to protect the complete spectrum of diversity.