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.
KeywordsBlack wildebeest Blue wildebeest Hybridization STRUCTURE HYBRIDLAB Microsatellites
The authors wish to express their sincere gratitude to the South African National Biodiversity Institute (SANBI) and International Foundation of Science (IFS), Grant Number B6411, for funding the analysis of pure and hybrid wildebeest populations. We also thank Ezemvelo KZN Wildlife, the Free State Department of Economic, Small Business Development, Tourism and Environmental Affairs (DESTEA) and South African National Parks (SANParks) for providing samples, and for prioritizing the wildebeest hybridization issue. The DST NRF Professional Development Programme through the NZG is thanked for supporting human capital.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
Black wildebeest samples were sanctioned under TOPS permit 036006 (University of the Free State) and a standing permit 03309 (National Zoological Gardens of South Africa). Samples from the Free State Provinces were collected under permit no. 01/30307 issued by DESTEA. Ethical clearance from the respective Institutional Research Ethics Committees was also obtained; UFS-AED2015/0067 (University of the Free State) and P7/12 (National Zoological Gardens of South Africa).
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