The western wildebeest: a natural hybrid between the black and blue wildebeests?

I have previously shown that what I call the western wildebeest

• should be distinguished from the blue wildebeest (Connochaetes taurinus taurinus), and
• already has a taxonomically legitimate name, viz. Connochaetes taurinus mattosi, which for mainly historical reasons has been overlooked.

Please see https://www.inaturalist.org/journal/milewski/67992-photo-pair-summarising-the-distinction-between-blue-wildebeest-and-western-wildebeest# and https://www.inaturalist.org/journal/milewski/54306-how-one-of-the-most-familiar-of-african-large-mammals-came-to-be-unrecognised#.

It is also known that the two South African spp. of wildebeests, namely C. taurinus and the black wildebeest (Connochates gnou), are capable of producing fertile hybrids (https://link.springer.com/article/10.1007/s10592-018-1071-x and https://link.springer.com/article/10.1007/s10344-011-0567-1).

The context in which hybridisation has been discovered is the holding of both spp. together, under artificial conditions, on game ranches. However, the natural distributions did overlap even under natural conditions, in and near what is now Free State province of South Africa, at the time of European arrival (https://www.researchgate.net/figure/Overlap-of-species-distribution-of-blue-and-black-wildebeest-Map-was-redrawn-from-IUCN_fig2_265128890 and https://www.researchgate.net/figure/Historical-distribution-ranges-of-blue-light-blue-and-black-wildebeest-greyThe_fig3_322539832).

In this Post, I hypothesise that the natural origin of C. t. mattosi has been by virtue of past (Pleistocene) hybridisation between C. taurinus and C. gnou.

I base this on the observation that most of the ways in which C. t. mattosi differs from C. t. taurinus are in line with the nature of C. gnou.

These are as follows.

Brindling is well-developed in C. t. taurinus (http://www.safari-club.co.uk/photo-galleries/kenya-familiarisation-trip-2010/dsc_0062/), minimally developed in C. gnou, and intermediate in C. t. mattosi.

The mane is lax in C. t. taurinus, vs stiff in C. gnou. In C. t. mattosi, the mane is stiff, making this the only form in the taurinus-complex that possesses a stiff mane.

The beard is lax and short in C. t. taurinus (https://www.gettyimages.com.au/detail/photo/close-up-of-blue-wildebeest-greater-kruger-national-royalty-free-image/81897934?phrase=blue%20wildebeest%20south%20africa&adppopup=true), vs stiff and relatively long in C. gnou (https://www.istockphoto.com/photo/black-wildebeest-gm887262280-246261777?phrase=wildebeest%20fur%20close%20up). In C. t. mattosi, the beard is far better-developed than in C. t. taurinus, and is particularly stiff (https://www.gettyimages.com.au/detail/photo/stripe-gnu-in-the-etosha-national-park-in-namibia-royalty-free-image/1297158239?phrase=blue%20wildebeest%20south%20africa&adppopup=true).

Sheen on the rump is noticeable in C. t. taurinus (albeit not as well-developed as in mearnsi or albojubatus), vs absent in C. gnou. In C. t. mattosi, sheen on the rump is hardly noticeable.

Paleness (depigmentation) on the proximal part of the mane (i.e. at the base of the mane) is well-developed in C. gnou, vs poorly-developed in C. t. taurinus. In C. t. mattosi, this feature seems to have an intermediate occurrence.

Infants tend to be paler (apart from the feet) in C. t. taurinus (https://www.gettyimages.com.au/detail/photo/side-view-of-buffalo-grazing-on-field-bushbuckridge-royalty-free-image/1347710373?phrase=blue%20wildebeest%20south%20africa&adppopup=true and https://www.alamy.com/stock-photo-baby-blue-wildebeest-connochaetes-taurinus-with-mother-21318646.html?imageid=B9A71E5D-12A8-4A62-992C-AAE26EA50A2A&p=50730&pn=1&searchId=4093b7b4151429bdd59b4c6faf51ee5c&searchtype=0 and https://www.reddit.com/r/wildlifephotography/comments/107gvvp/blue_wildebeest_with_suckling_calf_black_rhino/ and https://www.flickr.com/photos/antonettevdb/24818598341) than in C. gnou (https://www.youtube.com/watch?v=YQ-JJyS9HSo and https://www.irishnews.com/magazine/daily/2019/08/27/news/rare-baby-wildebeest-born-at-newquay-zoo-1696156/ and https://www.zooborns.com/zooborns/2009/07/newquay-welcomes-a-leggy-wildbeest.html).

In C. t. mattosi, the tone of infants seems intermediate (https://cloudfront.safaribookings.com/library/zambia/xxl/Liuwa_Plain_National_Park_041.jpg).

I can think of two alternative hypotheses for the origin of C. t. mattosi.

Firstly, C. t. mattosi may be a paedomorphic version of C. t. taurinus (https://www.inaturalist.org/journal/milewski/54384-the-western-wildebeest-as-an-example-of-paedomorphic-evolution#). This hypothesis is not mutually exclusive with the approach taken in the present Post.

Secondly, C. t. mattosi may have arisen by natural selection, free of any hybridisation, under ecological conditions different from those to which C. t. taurinus is adapted. South of the Kunene and Okavango Rivers, this seems to make sense, because C. t. mattosi is associated with Kalahari sand and semi-arid climates. However, it is undermined by the fact that C. t. mattosi extends deep into mesic south-central Africa, in the countries of Angola and Zambia.

Posted on January 20, 2023 01:12 AM by milewski