Diversification in insular plants: inferring the phylogenetic relationship in Aeonium (Crassulaceae) using ITS sequences of nuclear ribosomal DNA

The ITS regions of nuclear ribosomal DNA were sequenced in 37 species of the genus Aeonium . A phylogeny obtained through the use of parsimony agrees to some extent with the sectional division of the genus and confirms the position of two newly described species. It also suggests the potential importance of reticulate evolution in the genus. Based on the geographic distribution of this particular island group and the growth forms of its species, dispersal across similar ecological zones of different islands followed by adaptive radiation and isolation are suggested to be the prominent routes in speciation. As is typical of island genera, large polytomies at the distal nodes in the phylogeny indicate a recent rapid radiation.