Genetic differentiation among five populations of the South African ghost frog, Heleophryne natalensis

Abstract

Allozyme electrophoresis was used to analyse genetic heterogeneity in five ghost frog populations ( Heleophryne natalensis) ( Hewitt, 1913) from different localities in South Africa. A population of the congeneric H. purcelli, was used as a reference group. A total of 25 loci were resolved from 14 enzymes and an unspecified protein. Of the 25 loci resolved, eight were variable within or across populations, revealing an overall polymorphism of 32% but not more than 8% in any individual population. Four of the H. natalensis populations sampled were monoallelic, whereas the fifth population displayed an average heterozygosity of 2.97%. However, there was considerable variation among H. natalensis populations, including monomorphic populations, with fixed allelic differences at three loci. Gene flow among H. natalensis populations was 0.156–0.915 migrants per generation for four pairwise comparisons but zero for the remaining six pairs; the latter is unusual for conspecific populations. The overall intraspecific fixation index value for H. natalensis was 0.876, not much lower than the interspecific F ST value of 0.912 calculated when data for H. natalensis and H. purcelli was pooled for comparison. This confirms low gene flow and tight selection within microhabitats. Genetic distances ranged from 0.008 to 0.128 between conspecific populations, increasing to 0.182–0.284 between the H. natalensis populations sampled, and H. purcelli. The results are discussed with reference to the relationship between low genetic heterogeneity, response to selection and habitat tolerance of frogs.