Molecular cytogenetics of tragelaphine and alcelaphine interspecies hybrids: hybridization, introgression and speciation in some African antelope

Abstract

Hybridization can occur naturally among diverging lineages as part of the evolutionary process leading to complete reproductive isolation, or it can result from range shifts and habitat alteration through global warming and/or other anthropogenic influences. Here we report a molecular cytogenetic investigation of hybridization between taxonomically distinct species of the Alcelaphini (Alcelaphus buselaphus 2n = 40 × Damaliscus lunatus 2n = 36) and the Tragelaphini (Tragelaphus strepsiceros 2n = 31/32 × Tragelaphus angasii 2n = 55/56). Cross-species fluorescence in situ hybridization provides unequivocal evidence of the scale of karyotypic difference distinguishing parental species. The findings suggest that although hybrid meiosis of the former cross would necessitate the formation of a chain of seven, a ring of four and one trivalent, the progeny follow Haldane's rule showing F1 male sterility and female fertility. The tragelaphine F1 hybrid, a male, was similarly sterile and, given the 11 trivalents and chain of five anticipated in its meiosis, not unexpectedly so. We discuss these findings within the context of the broader evolutionary significance of hybridization in African antelope, and reflect on what these hold for our views of antelope species and their conservation.

Repeated hybridization of two closely related gazelle species (Gazella bennettii and Gazella subgutturosa) in central Iran

“…Other reported cases of interspecific hybridization in bovids have shown that even if the parent species have different chromosome numbers, female offspring can be fertile, for example, in an Alcelaphus buselaphus × Damaliscus lunatus cross reported by Robinson et al. (2015). So maybe one fertile female hybrid was enough to keep the subgutturosa haplotype in the G. bennettii population.…”

“…It is surprising therefore to find hybrids of the two species that seem to be fertile and interbreeding with pure G. bennettii in the wild. Interspecific hybrids in other bovid species (e.g., Alcelaphines, Tragelaphines) with (and without) different chromosome numbers were found to be infertile, at least in males (Robinson, Cernohorska, Schulze, & Duran‐Puig, 2015; Vaz Pinto et al., 2016).…”

Impacts of taxonomic inertia for the conservation ofAfrican ungulate diversity: an overview

“…In South Africa there has been considerable concern about introgression of southern blue wildebeest Connochaetes taurinus genes into the local endemic black wildebeest Connochaetes gnou following inopportune introductions of the former species into the latter's range (Grobler et al., ). But many more taxa seem affected; some cases have been discussed in detail, such as hybridizations between greater kudu and lowland nyala Strepsiceros strepsiceros × Tragelaphus angasi , or red hartebeest and tsessebe Alcelaphus buselaphus × Damaliscus lunatus (Robinson et al., ). Furthermore, admixtured populations of the Karoo and Kalahari springbok ( Antidorcas spp.)…”