Wahlert, Gregory A. , Ballard, H. E. .
Taxonomic affinities and biogeographic origins of the tree-violets (Rinorea, Violaceae) from Madagascar.
The island-continent of Madagascar is one of the world’s great biodiversity hotspots with ca. 12,000–15,000 species of plants. Rinorea (Violaceae) is a genus of shrubs and small trees with a pantropical distribution. Of the ca. 250 species, 40 occur in Madagascar and 110–150 in Africa. West Africa and Madagascar are centers of diversity for the genus where Rinorea can be a common understory species in perhumid and seasonally wet forests. Over the last 75 years, the affinities and origin of the Malagasy flora have been surmised from taxonomic and floristic studies. As molecular-based phylogenies of Malagasy genera become available, inferences can be made about the origins of particular groups and the flora in general. It is thought that the Malagasy flora is composed of both relict species left over from the break-up of Madagascar-India and from species arriving via long-distance dispersal, mainly from Africa, but also from Asia. Taxonomic studies of Paleotropical Rinorea, coupled with a chloroplast phylogeny, have lead to the identification of five lineages common to Africa and Madagascar. In one instance, directionality of dispersal from Africa to Madagascar is supported for the endemic Rinorea spinosa. An intriguing result of this study is the relationship of a sixth lineage of Malagasy Rinorea: the endemic, opposite-leaved subsect. Verticillatae. Morphologically, this group shows no affinity to any African or Asian group of Rinorea. However, trnL-F intron/spacer and trnD-E spacer sequences recover a well supported sister relationship between Verticillatae and Asian Rinorea. These taxonomic and molecular phylogenetic results suggest that there have been five dispersal events between Africa and Madagascar for Rinorea. Better resolution of the Paleotropical Rinorea is needed to infer an origin for the endemic Verticillatae.
Log in to add this item to your schedule
1 - Ohio University, Department of Environmental & Plant Biology, Porter Hall, Richland Avenue, Athens, Ohio, 45701-2979, USA
Presentation Type: Oral Paper:Papers for Topics
Location: Cottonwood D/Snowbird Center
Date: Wednesday, July 29th, 2009
Time: 8:45 AM