African adventures: Human-mediated hybridization between Common and Black-faced Impala

Translocation of subspecies resulted in the production of hybrids.

At the moment, I am teaching the course Animal Ecology with several colleagues. One part of this course is a modelling practical where students have to recreate a savanna model from a study in the journal Ecology. Once they get this model running, the students have to change it. They can introduce predators, simulate climate change or study the effects of diseases. Some students decided to focus on particular herbivore species, such as the impala (Aepyceros melampus). Recently, I came across a paper on hybridization between two impala subspecies in the journal Conservation Genetics. Let’s see what they found.

1200px-Red-billed_oxpecker_(Buphagus_erythrorhynchus)_on_impala_(Aepyceros_melampus)

Red-billed Buffalo Starling on the head of an impala female in Chobe National Park, Botswana © Charles J. Sharpe | Wikimedia Commons

 

Genetic studies

Taxonomists recognize two subspecies of impala: the black-faced impala (A. m. petersi) and the common impala (A. m. melampus). These subspecies have been geographically separated until humans started translocating them across southern Africa. This anthropogenically induced contact might lead to hybridization. However, previous studies – based on mitochondrial DNA and microsatellites – found no evidence for hybrid impalas. In a more recent paper, Susan Miller and her colleagues sampled in two Namibian locations: Etosha National Park and Southern Cross Private Game Reserve.

 

Hybrids

Using a set of 13 microsatellites, the researchers confirmed the genetic distinctness of the black-faced impala and the common impala. More importantly, the genetic markers could also be used to identify hybrid individuals: four in Southern Cross Private Game Reserve and two in Etosha National Park. However, the analyses were restricted to early generation hybrids. Backcrosses could not be detected with confidence. A genomic approach might uncover even more admixture between these subspecies.

impala_hybrid

(a) Black-faced male (b) possible hybrid male and (c) common impala male. From: Miller et al. (2020) Conservation Genetics

 

Translocations

These findings highlight the potential dangers of translocating animals across the globe. Although hybridization can be beneficial (e.g., transfer of adaptive alleles), it can result in the loss of local genetic variation. The impala situation is no isolated case, numerous other African herbivores have been moved across the continent, occasionally resulting in hybridization. Notable examples include blesbok (Damaliscus pygargus phillipsi) x bontebok (D. p. pygargus) and blue wildebeest (Connochaetes taurinus) x black wildebeest (C. gnou). Human-mediated hybridization is clearly an issue in Africa. Surprisingly, my students have not implemented this in their savanna models yet…

 

References

Miller, S. M., Moeller, C. H., Harper, C. K., & Bloomer, P. (2020). Anthropogenic movement results in hybridisation in impala in southern Africa. Conservation Genetics.

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