Royal Botanic Garden, 20a Inverleith Row, Edinburgh, Scotland. Begonia is one of the largest angiosperm genera, with 1400 species currently recognised. These were placed into 63 sections in the most recent taxonomic treatment. However, there is considerable uncertainty in both section inter-relationships and sectional composition, and there is no formalised phylogenetic hypothesis for the genus. Cladograms were produced for 35 Begonia , one Symbegonia and two Datisca species, for partial 26S and ITS sequence data.
Analyses suggest that African taxa are basal in Begonia .
The New Guinea genus Symbegonia is nested deeply within Begonia . Using a combined morphology - ITS analysis, the fit of individual morphological characters to a tree was examined. The correlation between phylogenetic relationships implied by the ITS tree and the geographical distributions of species was explored. As a general rule, related species are geographically proximal, suggesting limited dispersal of lineages. In contrast, morphologically similar but geographically separated species tend to be phylogenetically disparate.