GENETIC-VARIATION WITHIN AND GEOGRAPHICAL RELATIONSHIPS BETWEEN 4 NATURAL-POPULATIONS OF VIRGILIA OROBOIDES (TRIBE PODALYRIEAE, FABACEAE)

Virgilia oroboides has a large indigenous range encompassing most of t he south-western coastal areas of the Cape Province, South Africa, whe re it exhibits considerable morphological variation. Four populations of V. oroboides were examined by horizontal starch gel electrophoresis to assess levels and patterns of genetic variation and to estimate th e amount of genetic differentiation among populations at 37 protein co ding loci. Leaf extracts were surveyed for 22 proteins, and gene produ ts of 37 loci revealed genetic variation at 17 (46%) thereof. The perc entage of polymorphic loci range from 29.73-43.24% (0.95 criterion), v alues of 1.35-1.49 (+/- 0.09) were obtained for the mean number of all eles per locus, and average heterozygosities per locus were calculated at 0.127-0.198. No statistical significant difference between heteroz ygosity values was obtained when fewer (25 compared to 50) individuals were analysed. The mean genotypic distance index (Nei, 1978 = 0.0185) suggests a low degree of differentiation between populations. Geograp hic relationships reflect gradual isolation of the western populations , which may have become restricted to a few moist sites as a result of a decrease in total forest area in response to longterm climatic chan ges. This isolation and subsequent selection may have resulted in a de pletion of genetic variation from the eastern to the western regions. Estimates of elapsed divergence times suggest that these populations d iverged 0.02-0.18 million years ago. Copyright (C) 1996 Elsevier Scien ce Ltd