Assessing introgressive hybridization between Blue wildebeest (Connochaetes taurinus) and Black wildebeest (Connochaetes gnou) from South Africa.

Introgressive hybridization poses a threat to the genetic integrity of black wildebeest (Connochaetes gnou) and blue wildebeest (Connochaetes taurinus) populations in South Africa. Black wildebeest is endemic to South Africa and was driven to
near extinction in the early 1900s due to habitat destruction, hunting pressure and disease outbreaks. Blue wildebeest on the
other hand are widely distributed in southern and east Africa. In South Africa the natural distribution ranges of both species
overlap, however, extensive translocation of black wildebeest outside of its normal distribution range in South Africa have
led to potential hybridization between the two species. The molecular identification of pure and admixed populations is
necessary to design viable and sustainable conservation strategies, since phenotypic evidence of hybridization is inconclusive after successive generations of backcrossing. The aim of this study was to assess levels of hybridization in wildebeest
using both species-specific and cross-species microsatellite markers. Black wildebeest (157) and blue wildebeest (122) from
provincial and national parks and private localities were included as reference material, with 180 putative hybrid animals
also screened. A molecular marker panel consisting of 13 cross-species and 11 species-specific microsatellite markers was
developed. We used a Bayesian clustering model to confirm the uniqueness of blue- and black wildebeest reference groups,
assign individuals to each of the two clusters, and determine levels of admixture. Results indicated a clear partition between
black wildebeest and blue wildebeest (the average proportions of membership to black wildebeest and blue wildebeest
clusters were QI=0.994 and QI=0.955 respectively). From the putative hybrid samples, only five hybrid individuals were
confirmed. However, high levels of linkage disequilibrium were observed in the putative hybrid populations which may
indicate historical hybridization. Measures of genetic diversity in the black wildebeest populations were found to be lower than that of the blue wildebeest. The observed lower level of genetic diversity was expected due to the demographic history of the specie. This study will make a significant contribution to inform a national conservation strategy to conserve the genetic integrity of both species.