HUGHES, MARK*, PETER HOLLINGSWORTH, and TONY MILLER. Royal Botanic Garden Edinburgh, 20a Inverleith row, Edinburgh, Scotland. - Gene flow and speciation in Begonia.
The genus Begonia is one of the six largest angiosperm genera
in terms of species number. Studies of such large genera, from the
phylogenetic to the population level, can give insight into the
processes that generate plant biodiversity. Several properties of
Begonia suggest that restricted capability for gene flow
through pollen and seed dispersal has been important in generating its
species diversity. These are: (i) Monophyletic groups in
Begonia show strongly restricted geographical distributions,
suggesting repeated allopatric speciation events. (ii) The level of
narrow range endemism of Begonia is very high, suggesting
species ranges are dispersal limited. (iii) Widespread species are
rare, and tend to show marked morphological variation, suggesting low
intra-specific gene flow over moderate to large scales. (iv)
Begonia has over 1400 species, but few obvious major
innovations - the majority of Begonia appear broadly
ecologically similar. Species from the Socotra archipelago (B.
socotrana and Begonia sp. nov.) and South Africa (B.
sutherlandii) are being used to investigate gene flow and
population structure in Begonia, with the aid of microsatellite
markers. A combination of population genetic, phylogenetic and
distributional data represents a potential data set for understanding
the processes that have led to these observed patterns of
Key words: Begonia, microsatellites, speciation