Natural hybridization and gene introgression between Xenopus gilli and Xenopus laevis laevis (Anura: Pipidae)

Abstract

The rare Xenopus gilli is restricted to the southern tip of South Africa where it occurs sympatrically with the much more numerous Xenopus laevis laevis. Specimens of intermediate phenotype are occasionally found on the Cape Flats, and a sample of these was examined for evidence of hybridization. Serological, immunological and reproductive studies showed that one female was an F1 hybrid between X. gilli and X. I. laevis; a second female, which exhibited one X. gilli specific serum protein amongst otherwise laevis characters, demonstrated introgression of gilli genes into the laevis species. Cross‐breeding between the two sympatric Xenopus species represents a danger for the survival of the already‐vulnerable X. gilli. The genetic behaviour of hybrids also carries implications of evolutionary potential, on the one hand creating gene flow between species, and on the other hand capable of generating new polyploid hybrid species. There is evidence that allopolyploidy has been an important process in the evolution of Xenopus.