Chloroplast DNA restriction site phylogeny of the genus Androcymbium (Colchicaceae)

Abstract

We examined phylogenetic relationships among 51 populations representing 18 of the approximately 40 currently recognized species in the genus Androcymbium using 559 parsimony informative cpDNA restriction site changes. Our results indicate that the genus is monophyletic and had a southern African origin. According to our estimates of divergence times, species distributed in North Africa arose in the early Miocene from an ancestor related to A. euconoides. The two Canary Island endemics originated from an ancestor related to the North African A. wyssianum in the early Pliocene. Strong support for the monophyly of all the species represented by more than one population casts doubt on the inclusion of the six North African species into a Androcymbium gramineum complex and provides strong evidence against the possibility of reticulation in these species. Lack of support for the monophyly of the two currently recognized sections (Androcymbium and Erythrostictus) suggests that the presence of wing-like appendages on the tepals is not a reliable taxonomic character for sectional circumscription. Molecular clock estimates emphasize the importance of ecological diversity in the differentiation of South African species. In sharp contrast, the much less pronounced pattern of change among north African species seems to have been fostered by their relatively recent origin and by the uniform ecological conditions that prevail in their areas of geographic distribution.