GENETIC DIVERSITY AND GENE FLOW IN THE MORPHOLOGICALLY VARIABLE, RARE ENDEMICS BEGONIA DREGEI AND BEGONIA HOMONYMA (BEGONIACEAE)
Date
2012-02-03
Authors
MATOLWENI, LUZUKO ORLYN
BALKWILL, KEVIN
MCLELLAN, TRACY
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Abstract
Excellent models for the study of evolutionary pro¬cesses are often provided by taxa that pose the greatest problems in systematics (Wolf, Soltis, and Soltis, 1991). Endemic plants provide a superb tool for studying the dynamic processes of speciation and evolution, particu¬larly island endemic plants (Ito and Ono, 1990; Aradya, Mueller-Dombois, and Ranker, 1991; Barrett, 1996). Ev¬idence of most evolutionary events that formed continen¬tal biota has been lost because such biota are so ancient (Carson, 1987). Complex patterns of variation may blur species boundaries and lead to taxonomic complexity.
Description
Begonia dregei and B. homonyma (Begoniaceae), rare plants endemic to coastal forests of eastern South Africa, are two closely related species with high levels of variation among populations in the shape of leaves. Distribution of genetic variation and genetic relatedness were investigated in 12 populations of B. dregei and seven of B. homonyma using polyacrylamide gel electrophoresis. Twelve of the 15 enzyme loci examined were polymorphic, but only seven loci were polymorphic within at least one population. Genetic diversity measures indicated that the among-population gene differentiation represents >90% of the total genetic component in both species considered individually or combined. This indicated restricted gene flow, consistent with the limited dispersal abilities of Begonia generally and the ancient separation of isolated forest patches. Genetic distances among populations are much higher than usually found within species. Allozyme data provide no support for the recognition of B. dregei and B. homonyma as distinct species.
Keywords
African coastal forests, Begonia, Begoniaceae, genetic drift, genetic population structure, habitat frag¬mentation