Management of hybridization in an endemic species: decision making in the face of imperfect information in the case of the black wildebeest—Connochaetes gnou

Abstract

Hybridization between introduced and endemic ungulates, resulting from Anthropogenic actions, have been reported for several species. Several studies of such events contain the common themes of extralimital movements, problematic phenotypic and genetic detection, and imperfect management. In southern Africa, the endemic black wildebeest (Connochaetes gnou) currently faces a serious threat of hybridization and introgression. This species survived near extinction and consequent genetic bottlenecks in the late 1800s and in the 1930s. Initiatives by private farmers followed by conservation authorities led to a dramatic recovery in numbers of this species. However, in an ironic twist, the very same advances in conservation and commercial utilisation which lead to the recovery of numbers are now themselves threatening the species. Injudicious translocation has brought the species into contact with its congener, the blue wildebeest (Connochaetes taurinus), and in recent times, hybridization between the species has occurred at numerous localities in South Africa. Consequently, a significant proportion of the national black wildebeest population potentially carries a proportion of introgressed blue wildebeest genetic material. We discuss completed and ongoing attempts to find molecular markers to detect hybrids and highlight the difficulty of detecting advanced b a c k c r o s s e s . A d d i t i o n a l a v e n u e s o f r e s e a r c h , s u c h a s w o r k o n m o r p h o l o g y ( c r a n i a l a n d postcranial elements), estimating of the probability of introgression and modelling of diffusion rates are also introduced. In addition to the difficulty in detecting hybrid animals or herds, the lack of consensus on the fate of hybrid herds is discussed. Finally, in an environment of imperfect information, we caution against implementation of management responses that will potentially induce a new genetic bottleneck in C. gnou.

Where is the game? Wild meat products authentication in South Africa: a case study

“…Hybridization between wildebeest species is known in South Africa as a result of anthropogenic translocations beyond their natural geographic range [48]. This phenomenon is reflected among our reference South African blue wildebeest samples, which cluster with black wildebeest (Figure S1c in Additional file 3).…”

‘Intentional Genetic Manipulation’ as a conservation threat

“…Grobler et al 2011) and as such, alleles at high frequencies in ranched animals could potentially circulate undetected in natural populations, especially if recessive. Selection against desirable phenotypes (unnatural selection) may decrease survival in the wild (Allendorf and Hard 2009).…”

“…3; Supplementary material 3). However, farming both species on the same land with few or no con-specific mates may encourage hybridisation (Grobler et al 2011;Dalton et al 2014) and this is a general risk of game farming (e.g. Blanco-Aguiar et al 2008).…”

Interspecific hybridization between greater kudu and nyala

“…Within Tragelaphini there have been previous reports of hybridization, for example between eland (Taurotragus oryx) and greater kudu, as well as between eland and sitatunga (Tragelaphus spekeii) (Gray 1971). Hybridization has also been reported in a number of other ungulate taxa in South Africa such as the blue (Connochaetes taurinus) and black wildebeest (C. gnu) (Grobler et al 2011). Anthropogenic hybridization occurs due to human interference and may lead to breeding of previously reproductively isolated taxa.…”