Vortrag, Island Biology 2014, Honolulu, Oahu, Hawai'i, USA: 07.07.2014 - 11.07.2014
Biodiversity and endemism follow distinct and non-random spatial patterns determined by a multitude of environmental conditions. So far research has focused on large scales, while our understanding of the drivers of these patterns on local or landscape scales is limited. For oceanic islands climatic drivers and topographic complexity have been suggested as important drivers. Here, we test the influence of climatic variability, climatic rarity and habitat diversity on species richness, endemic richness and percentage of endemics. We use endemic plant species on La Palma, Canary Islands, which is especially suited because it possesses strong environmental gradients, large natural areas and many single-island endemic species. We sampled a very extensive high-resolution dataset (n=890, 100x100m resolution) covering all relevant environmental conditions. Species richness increases with climatic stability and habitat diversity but decreases with climatic rarity. The percentage of endemics increases with climatic variability and climatic rarity. Endemic richness increases with habitat diversity. Contradictory to previous findings, climatic variability, which is associated to extreme conditions, supports speciation, while species richness is fostered by stable conditions. Most species colonizing islands are adapted to common (mesic) conditions, while rare (extreme) climates offer more available niche space for speciation. High habitat diversity leads to more ecological opportunities for both native and endemic species to occupy and more protection from extinction via micro-refugia. Our findings contribute to the fundamental understanding of small-scale spatial patterns of biodiversity and endemism not only on islands, but also in other terrestrial biomes. Climatic rarity is a promising concept for future research.