Origin and evolution of the endemic genera of Gonosperminae (Asteraceae: Anthemideae) from the Canary Islands: evidence from nucleotide sequences of the internal transcribed spacers of the nuclear ribosomal DNA

摘要

The Gonosperminae (Asteraceae) are composed of three genera endemic to the Canary Islands (Gonospermum Less., and Lugoa DC.) and southern Africa (Inulanthera Källersjö), and they are considered an example of a floristic link between these two regions. Phylogenetic analyses of ITS sequences reveal that the Canarian genera are not sister to Inulanthera and do not support the monophyly of the Gonosperminae. These results, coupled with previous phylogenetic studies of other groups, suggest that many of the putative biogeographic links between Macaronesia and southeast Africa need to be evaluated by rigorous phylogenetic analyses. Inulanthera forms part of the basal southern African radiation of the Anthemideae, and therefore it is closely related to other taxa from this region. Maximum likelihood and weighted parsimony analyses support a monophyletic group in the Canary Islands, that includes Lugoa, Gonospermum, and three Tanacetum species endemic to the island of Gran Canaria. Bootstrap support for the monophyly of this Canarian group is weak, and it collapses in the strict consensus tree based on unweighted parsimony. Lugoa is nested within Gonospermum, and both interisland colonization among the western islands of La Gomera, El Hierro, La Palma and Tenerife, and radiation on the central island of Gran Canaria have been the major patterns of species diversification for these Canarian endemics.