Poster, EURECO – 11th European Ecological Conference of the European Ecological Federation jointly with the GFOE – 38th Annual Conference of the Ecological Society of Germany, Austria and Switzerland, Leipzig: 15.09.2008 - 19.09.2008
Abstract:
The Canary Islands are a place of pilgrimage for ecologists since the time of Alexander von Humboldt and Charles Darwin. Even if there is still some debate on the taxonomic status of some endemic species, there exists an excellent quality of biotic data that can be used for biogeographical analyses. In this study we analyse island specific data for the following groups: Spermatophyta, Pteridophyta, Bryophyta, Lichenes, Fungi, Chordata, Arthropoda, Mollusca. Species diversity on islands depends on evolutionary processes, migration and dispersal abilities. The species pool on Continental Africa, however, is not constant. Today only few habitats on the continent can host comparable communities for Canarian ecosystems. The special situation that the source species pool of the African continent became quantitatively extinct due to climate change during the Holocene, is a remarkable fact that distinguishes the situation from many other island floras and faunas. Interdependencies between species richness and endemism are under debate. Large species pools may on the one hand increase competitive exclusion and predation and therefore increase the risk of extinction for a single species. On the other hand species are forced to react to ecological pressure by adaptation. As a result large species pools might offer more options for evolutionary processes and speciation or in other words: species diversity drives speciation. However, correlations found are not necessarily reflecting general functional processes. With our data set we are able to tackle evolutionary theories and deepen the discussion specifically for groups of organisms with varying mobility and turn-over. In addition, the Canary Islands offer a wonderful experiment to prove the theory of island biogeography and to extend this theory to variables such as habitat heterogeneity and functional connectivity. Besides the alpha-diversity and species pool of separate islands and the total species pools for the considered groups of organisms, we address also beta-diversity relationships between islands. Here we identify also considerable differences in the similarity patterns between organismic groups.