TEBBITT, MARK C.1, LAURA L. FORREST2, W. SCOTT HOOVER3, and SUSAN M. SWENSEN4.* 1Brooklyn Botanic Garden, New York, U.S.A.; 2Royal Botanic Garden Edinburgh, Scotland; 3New England Tropical Conservatory, Mass., U.S.A.; 4Ithaca College, New York, U.S.A. - Relationships of fleshy fruited Asiatic Begonia (Begoniaceae) based on ITS sequence data and restriction site mapping of PCR amplified chloroplast and mitochondrial fragments.
Begonia is a large pantropical genus of herbs, shrubs and
lianas. A wide variety of dispersal mechanisms have been recorded from
the genus. The majority of the c. 600 Asiatic species of the genus
have dehiscent, winged, capsular fruits and appear to be adapted to
either wind or rain-splash seed dispersal. However, c. 25 Asiatic
species have indehiscent, baccate fruits that usually lack wings and
appear to be adapted for animal dispersal. This morphologically
diverse group of fleshy-fruited species has traditionally been
classified in the section Sphenanthera, which is distinguished
from other Asiatic Begonia sections on this character alone. In
order to determine whether the section Sphenanthera represents
a monophyletic species group, nuclear, chloroplast and mitochondria
markers were analysed cladistically for a representative sample of
species from section Sphenanthera and from 11 of the 17 other
Asiatic sections. Begonia species from Africa were used as
outgroups in these analyses. Begonia section
Sphenanthera was found to be polyphyletic, indicating that
baccate fruits have evolved multiple times within Asia. The
evolutionary significance of animal dispersed and rain-splash
dispersed seed are discussed in the light of these analyses, and
changes to the sectional classification of these fleshy-fruited
Asiatic species are proposed.
Key words: Asia, Begonia, biogeography, classification, section Sphenanthera, seed dispersal