Monday, July 13, 2015

[Botany • 2011] Begonia afromigrata • Pliocene Intercontinental Dispersal from Africa to Southeast Asia highlighted by the New Species of Begonia sect. Tetraphila (Begoniaceae) from Laos and Thailand

Begonia afromigrata J.J. de Wilde
Fig. 1. Habit and morphology of Begonia afromigrata: A, upper leaf surface; B, lower leaf surface; C, male inflorescence; D, habit; E, male flower; F, androecium (top, side, and bottom view); G, female flower; H, side view of female flower and ovary.
All based on Rodda & Simonsson MR106 & M R107. || de Wilde et al. 2011

A new Begonia species from Laos and Thailand is described. It belongs to Begonia sect. Tetraphila, along with 30 other species which are all endemic to Africa. This is the first record of any of the 65 currently accepted sections in Begonia transgressing continental borders. A dated molecular phylogeny places the split of the new Asian species from its African congeners during the late Miocene to the early Pleistocene. As the species is a hygromesophilous epiphyte limited to tropical forest, no suitable corridor for migration existed during that time and the cause of the Afro-Asian disjunction probably is a long-distance dispersal event. The discovery of Begonia afromigrata emphasises the importance of chance in the assembly of tropical floras.

Keywords: Begonia sect. Tetraphila; long-distance dispersal; phylogeny 

Habitat and ecology. – Without exception in field notes the plant is described as epiphytic, growing between 5 and 15 m above ground level. It has been noted as growing on a Spondias species (Anacardiaceae; P. Tribune, pers. comm.). Usually collected on dead trees or fallen branches in evergreen forest (more rarely deciduous forest) on limestone, between 600 m and 1900 m altitude. Found more often on tree trunks than smaller branches. Plants cultivated from cuttings always produce one or more male inflorescences first, followed later by female inflorescences.

de Wilde, J.J.F.E., Hughes, M., Rodda M. & Thomas D.C. 2011. Pliocene Intercontinental Dispersal from Africa to Southeast Asia highlighted by the New Species Begonia afromigrata (Begoniaceae). Taxon 60: 1685-1692.