Conservation genetics of the Western Derby eland (Taurotragus derbianus derbianus) in Senegal: integration of pedigree and microsatellite data

Abstract

Less than 200 wild individuals of the critically endangered Western Derby eland (Taurotragus derbianus derbianus) live in the Niokolo Koba National Park (NKNP) in Senegal. A semi-captive breeding programme was established in 2000 with six founding individuals (one male, five females) transferred from the NKNP. In 2013, the population consisted of 92 individuals living in seven separate herds in the two fenced reserves of Bandia and Fathala in Senegal. Because of the low number of founding individuals in the breeding programme and the resulting high kinship, we compared the results from genealogical and genetic approaches to assess the level of genetic diversity. We used the data from the founder, F1 and F2 generations. In F1, the founder contribution was highly biased towards the only founding male, which sired all the offspring. In F2, the founder contributions were more balanced, as the male descendants of founding females entered the reproduction. This resulted in higher genetic diversity and lower inbreeding (based on pedigree data) in F2 than in F1. Results of molecular analysis using microsatellite loci confirmed the highest level of heterozygosity and lowest level of inbreeding in the founder generation; however, the implementation of a management strategy was not reflected in the empirical results. The results differed for F2, where empirical values of heterozygosity continued to decrease and inbreeding continued to increase. However, the allelic richness corresponded with the results of pedigree analyses, reflecting the more equalized founder contributions. We conclude that the overall results for genetic parameters were comparable with other breeding programmes for endangered ungulates. Nevertheless, we suggest the use of comprehensive molecular data to refine the studbook and to correct relatedness of founders and assign the missing paternities. Our suggestions correspond with the Western Derby Eland Conservation Strategy and confirm the need to introduce new founders into the semi-captive population, in order to minimize the risk of inbreeding depression and improve genetic diversity and suitability for potential reintroduction.