Phylogenetic relationships of Asian Begonia, with an emphasis on the evolution of rain-ballist and animal dispersal mechanisms in sections Platycentrum, Sphenanthera and Leprosae.

摘要

While most Begonia species have a similar fruit morphology that shows adaptations to wind dispersal, a few species have atypical fruits and are adapted to either animal or rain dispersal. Such differences in fruit morphology have traditionally been emphasized in sectional classifications of Begonia and some of the currently recognized sections can only be distinguished using ovary and fruit characteristics. We evaluated the monophyly and evolution of three Asian sections with atypical fruit morphologies: Platycentrum, Sphenanthera, and Leprosae, along with members of nine other Asian sections with fruit morphologies typical of wind dispersed Begonia. A parsimony analysis of nrDNA ITS/5.8S sequence data of 46 Asian Begonia species suggests that the members of section Platycentrum, which have fruit morphologies indicative of rain dispersal, evolved from wind dispersed Asian taxa following the colonization of wetter habitats. From within this rain dispersed group, species of section Sphenanthera with fleshy, animal dispersed fruits subsequently evolved on multiple occasions. Members of section Leprosae, which have fleshy fruit, evolved on two separate occasions, in one case independently of the members of the sections Platycentrum and Sphenanthera. As currently recognized, sections Platycentrum, Sphenanthera and Leprosae are polyphyletic..