Did mountain zebras arise evolutionarily by hybridisation between Equus grevyi-type and Equus quagga-type?

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In the genus Equus, hybrids between species tend to be infertile, as seen in mules and hinnies (https://en.wikipedia.org/wiki/Mule).

Hybridisation between Equus grevyi (https://www.inaturalist.org/taxa/43339-Equus-grevyi) and Equus quagga boehmi (https://www.inaturalist.org/observations?taxon_id=447363) would seem unlikely for additional reasons, viz.

• the former is larger-bodied than the latter, and
• the two spp. are thought to belong to different subgenera (Dolichohippus vs Hippotigris).

However, hybridisation between E. grevyi and E. q. boehmi has indeed occurred.

As it happens, the appearance of the hybrids raises an intriguing possibility.

This is that mountain zebras (the clade represented today by Equus zebra and Equus hartmannae, https://www.inaturalist.org/taxa/43330-Equus-zebra) may possibly have arisen from hybridisation between relatives of E. grevyi and relatives of E. quagga, in southern Africa.

On Ol Pejeta Conservancy (https://en.wikipedia.org/wiki/Ol_Pejeta_Conservancy), in the Laikipia district of Kenya, there has arisen a small population, reputed to be more than eight individuals, of a hybrid between Equus grevyi and Equus quagga boehmi (https://www.sciencedirect.com/science/article/abs/pii/S0003347215001669).

This hybridisation occurred because this reserve has been home to several lonely male individuals of E. grevyi, which have mated with females of the local - and fully indigenous - population of E. q. boehmi.

I have collected photos of these hybrids, scattered on the Web, and I encourage readers to take screenshots, and make printouts, before these vanish electronically, owing to the usual attrition.

Equus grevyi and E. quagga have patterns, on the rump, of striping so different that it would have been hard to anticipate how any hybrid could reconcile these patterns.

The parental patterns are:

• Equus grevyi https://www.shutterstock.com/image-photo/zebra-patterns-53151385 and https://www.shutterstock.com/image-photo/zebra-butt-zoo-1134759056 and https://www.shutterstock.com/image-photo/3-grevys-zebras-rears-3539043 and https://www.shutterstock.com/image-photo/four-zebra-butts-zoo-38649178 and https://www.shutterstock.com/image-photo/pair-zebras-back-side-butts-camera-511682623, vs
• Equus quagga boehmi https://www.alamy.com/the-rump-of-a-zebra-image336302894.html and https://www.shutterstock.com/image-photo/zebra-butt-327120779 and https://www.shutterstock.com/image-photo/two-zebras-butt-ngorongoro-crater-tanzania-1672540105 and https://commons.wikimedia.org/wiki/File:Zebra_butt_%2835305159642%29.jpg and https://www.shutterstock.com/image-photo/zebra-looking-back-shoot-behind-butt-472684030.

See https://www.animalspot.net/wp-content/uploads/2022/05/Types-of-Zebras.jpg.

Unexpectedly, what the hybrids do, in fact, show is a semblance of the pattern seen in mountain zebras (Equus hartmannae https://www.shutterstock.com/image-photo/zebra-showing-butt-1325349092 and https://www.pikist.com/free-photo-stbsq and https://www.news24.com/news24/video/southafrica/news/watch-the-battle-for-the-cape-mountain-zebras-future-20180514 and https://legacy.hoglezoo.org/meet_our_animals/animal_finder/hartmanns_mountain_zebra/ and https://www.flickr.com/photos/berniedup/32924156561 and scroll in https://observation.org/species/239297/).

This raises the possibility that mountain zebras originally arose by means of a similar hybridisation.

If so, then an obvious candidate would be the recently extinct species Equus capensis, which was the southern version of E. grevyi (https://www.researchgate.net/publication/233368144_Distribution_and_history_of_the_Cape_zebra_Equus_capensis_in_the_Quaternary_of_Africa and https://en.wikipedia.org/wiki/Equus_capensis and https://vera-eisenmann.com/IMG/pdf/128.E.capensis.pdf and https://philpapers.org/rec/CHUDAH and https://journals.co.za/doi/10.10520/EJC91909).

Additionally, there is evidence of hybridisation between Equus zebra and Equus quagga burchellii:
https://journals.co.za/doi/abs/10.3957/056.047.0059?utm_source=TrendMD&utm_medium=cpc&utm_campaign=South_African_Health_Review_TrendMD_0
 
PHOTOS OF HYBRID ON OL PEJETA CONSERVANCY, KENYA

https://www.alamy.com/africa-kenya-laikipia-plateau-northern-frontier-district-ol-pejeta-conservancy-hybrid-zebra-cross-between-a-grevys-zebra-image385051693.html

http://safaritalk.net/topic/11790-not-a-real-trip-report-kenya-november-2013/

https://www.alamy.com/africa-kenya-laikipia-plateau-northern-frontier-district-ol-pejeta-conservancy-hybrid-zebra-cross-between-a-grevys-zebra-image385051539.html

https://www.thepaintboxgarden.com/safari-kicheche-laikipia-part-2/hybrid-giraffe-ol-pejeta/

https://www.alamy.com/africa-kenya-laikipia-plateau-northern-frontier-district-ol-pejeta-conservancy-hybrid-zebra-cross-between-a-grevys-zebra-image385051600.html

https://www.reddit.com/r/wildlifephotography/comments/ubnsde/do_not_run_away_from_your_troublesrun_towards/

http://www.sushilchauhan.com/npcs/zebra_4(2).jpg
 
https://i.pinimg.com/originals/d5/fc/85/d5fc8578d10ec82ac52ef6a64f642128.jpg
 
http://www.thepaintboxgarden.com/wp-content/uploads/2016/05/Hybrid-giraffe-Ol-Pejeta.jpg
 
https://cdn.audleytravel.com/-/-/79/232184025140028012237198019008128026229176082161.jpg
 
https://scavenging.files.wordpress.com/2009/03/zebra_burchell_grevy.jpg?w=300&h=213 

Scroll in https://www.grevyszebratrust.org/conservation-status/

https://www.wildlifeofkenya.com/categories/ongulates/zebra-hybrid/

https://twitter.com/realscientists/status/1192736560212594688?lang=zh-Hant

https://twitter.com/realscientists/status/1192736560212594688

https://www.researchgate.net/figure/Plains-zebra-Equus-burchelli-a-hybrid-and-a-Grevys-zebra-Equus-grevyi-in-a-common-herd_fig3_227626401

Posted on 08 de setembro de 2022, 09:26 AM by milewski