**4.2 Refuge** *Begonia*

The limited dispersal of many *Begonia* makes them a useful group to search for the biogeographic signature of refugia (Sosef, 1994). Refugia are regions where vulnerable lineages could survive periods of dramatic climate change, such as ice ages. When the climate becomes favorable again, species disperse outwards from the refugia. This generates a distinctive pattern in the geographic distribution of genetic diversity, with former refugia having greater genetic diversity. The poor dispersal of *Begonia* means regions with high numbers of *Begonia* species are possible former refugia. Species of the African sections *Loasibegonia* and *Scutobegonia* are restricted to humid and shady locations and are proposed to have been especially sensitive to the period of Pleistocene climate oscillations, and dispersed slowly afterwards (Sosef, 1994). Centers of diversity for these sections are situated in West and Central Africa. Plana et al. (2004) also used *Begonia* diversity to identify the island of Sao Tome as a pre-Pleistocene refuge, and suggested different mainland areas in West Africa as refuges. It is quite possible that a number of different refugia existed for lineages with different ecological tolerances.
