The significance of geological traits for the speciation of endemic angiosperms on El Hierro (Canary Islands)
Von Gaisberg, Markus; Stierstorfer, Christian
A complete floristic and phytosociological database has been established for the Canary island of El Hierro. The combined evaluation of both data sets allows to advance hypotheses about the possible causes for the intra-island patterns of phytodiversity. As an example, the diversity hot spots of the El Hierro endemics are highlighted. There is a strong spatial correspondence between a high density of these endemics and geologically old surfaces in steep cliffs which have not been covered by relatively young lavas of rift volcanism. In contrast, the species density of the total flora generally increases with precipitation and human impact. Anthropogenic influences as a reason for the distribution pattern of the El Hierro endemics, however, can be excluded from the analysis of the phytosociological data. The endemics grow in specific plant communities of steep slopes with outcropping old geological series, which can also be supposed to be the centres of speciation of most of these taxa.