Interspecific hybridisation between the mallard and yellow-billed duck inSouth Africa

Abstract

Interspecific hybridisation is the interbreeding of genetically distinct groups and can lead to introgression, the exchange of genetic material between species, thereby leading to a loss of local genetic adaptations and genetic diversity. Hybridisation is a significant threat for dabbling ducks where interbreeding with the closely related invasive Mallard (Anas platyrhynchos) is extremely common. Mallards have been introduced into South Africa, and phenotypic evidence now suggests that they are hybridising with the native Yellow-billed Duck (Anas undulata). The aim of this research was to estimate the presence and extent of hybridisation between Yellowbilled Ducks, representing populations in central and north-west South Africa, and the introduced Mallard. Two mitochondrial DNA markers, cyt b and COI, and eleven microsatellite markers were used to assess genetic variation between these species and their putative hybrids. The microsatellite markers showed no significant admixture within the putative hybrids, however, one phenotypic Mallard sample showed significant admixture. The mitochondrial DNA markers separated the Mallards and Yellow-billed Ducks, and grouped the putative hybrids with the latter. Both the microsatellite and mitochondrial DNA markers were found to be successful at identifying admixture between Mallards and Yellow-billed Ducks, and separating these species both inter- and intra-specifically. However, an insufficient number of markers were used to infer backcrossed or late generation hybrids, and sampling was too localised to determine if hybridisation is occurring at different rates across South Africa. Future research should focus on wholegenome sequencing of the Yellow-billed duck to develop more markers, and sampling should occur throughout South Africa to better determine the different rates at which hybridisation may be occurring.