Vortrag, Jahrestagung des Arbeitskreises Biogeographie (VGDH), Basel: 07.05.2015 - 09.05.2015
High elevation islands, especially in the tropics and subtropics, are global hotspots of plant diversity. Owing to the continental-scale environmental gradients on the landscape scale of a medium-sized oceanic island, high elevation island can be considered climatic mini-continents, highlighting that the insights gained here might be relevant for other non-insular systems. Thus, understanding the underlying drivers of diversity, particularly regarding in-situ evolved endemic species, and the disturbances that shape them may offer fundamental insights into general ecological processes. In this study I assess (a) which environmental drivers (esp. topography and climate) determine the distribution of endemic richness, endemicity (percentage of endemics) and endemic rarity, and (b) how globally relevant disturbances (introduced herbivores, fire, roads) affect endemic diversity. I use the high elevation island of La Palma (Canary Islands) as a model system, where we recorded endemic species in almost 1000 plots and used fenced exclosure established by the NP Caldera de Taburiente in 2000 in the high elevation ecosystem. While topography mainly determined endemic richness, climate was most important for endemicity and endemic rarity. As a consequence, the spatially decoupled diversity hotspots highlight the importance for conservation managers to consider a broad spectrum of diversity measures. Introduced herbivores have a strong negative impact, whereas fire seems to positively affect high elevation plant diversity. Massive conservation efforts are needed to preserve highly threatened endemics in the high elevation ecosystem, including large fenced exclosures and population control of introduced herbivores. Surprisingly, roads have a positive effect on endemic richness, probably because rupicolous endemics are adapted to roadside cliff conditions and are protected from other anthropogenic disturbances. High elevation islands allow us to study how the interplay of eco-evolutionary processes and anthropogenic disturbances shape diversity patterns.