Origin of the Rapa endemic genus Apostates: Revisiting major disjunctions and evolutionary conservatism in the Bahia alliance (Compositae: Bahieae)
Published Web Locationhttps://doi.org/10.12705/655.8
Molecular phylogenetic analyses of nuclear and chloroplast DNA sequences indicate that the rediscovered Apostates, known only from Rapa in the Austral Islands of southeastern Polynesia, represents an example of extreme long-distance dispersal (> 6500 km) from southwestern North America and one of at least four disjunctions of comparable magnitude in the primarily New World Bahia alliance (tribe Bahieae). Each of the disjunctions appears to have resulted from north-to-south dispersal since the mid-Miocene; three are associated with such marked morphological and ecological change that some of the southern taxa (including Apostates) have been treated in distinct genera of uncertain relationship. Phyllotaxy within the Bahia alliance, however, evidently has been even more conservative evolutionarily than reflected by previous taxonomies, with alternate-leaved and opposite-leaved clades in Bahia sensu Ellison each encompassing representatives of other genera that share the same leaf arrangements. A revised taxonomic treatment of the Bahia alliance is proposed to recognize morphologically distinctive, monophyletic genera, including the critically endangered Apostates.