Differences between the quagga and other zebras

It has been established that the quagga is a subspecies of the plains zebra because it clusters genetically within this clade. This, however, does not imply that it does not differ considerably from other zebra species or subspecies. It diverged from the other plains zebra subspecies between 290 000 or 120 000 years ago [1], what is considerably longer ago than the differentiation between the lineage leading to domestic horses and Przewalski’s horse and definitely long enough to develop its own distinct traits. 

The most obvious difference between the quagga and other zebras is the fact that only the anterior part of the body was striped, while the posterior half was stripeless and of a brownish colour. The coat colour, or rather the extent of the striping, varies considerably in the 24 individuals of which the skin was preserved. I illustrated and described this variation in this post. Alas, the locality of the specimen has not been documented, so that the claim that the stripe reduction of the quagga represented a cline cannot be verified for at least within the quagga itself. 

Also, the quagga apparently had an idiosyncratic call (sounding like “kwa-ha-ha”, other variations are documented as well), of which the name of the animal is said to be an onomatopoeic derivation (Wikipedia). EDIT: It is possible that the quagga's call was identical with that of other plains zebras. 

Another very important distinct trait of the quagga is its sexual dimorphism. Preserved quagga skins suggest that the mares were longer and taller and thus larger than the males, which is the opposite of what we see in other zebras, including the plains zebra, where the males are larger than the females [2]. This is unique among extant equines. 

Another possible difference between the quagga and other plains zebra subspecies is the mane length. Looking at photographs of the 24 quagga skins preserved plus the photos of the only living mare to be photographed in the 19^th century, it appears to me that the mane is shorter than in other plains zebras. Of course this has to be verified by actually measuring the mane hair and comparing it to the other subspecies, but it seems rather apparent to me. 

 

My coloured version of the photo of the only quagga to be photographed, drawn with GIMP

Thus, it has to be concluded that the quagga was, despite being nested genetically within the plains zebra species, a distinct type of zebra with unique autapomorphies. This has consequences for the guideline of the Quagga Project. The quagga is evidently more than a colour variant, even though its range might have been continuous with that of other plains zebra subspecies (we find this also in species that form a hybrid zone, such as species within Bombina, Corvus, or Loxodonta to name a few). The similarity between the quagga and the zebras of the Quagga Project will merely be superficial. But, so claims the Quagga Project, the quagga was defined only based on external features, thus making that argument invalid. However, the overwhelming majority of animal (and plant) species on this planet is described on a phenotypic basis, it’s part of the requirements of the ICZN for a valid species description. Furthermore, the differences in the fur colour are not the only defining quagga characters, as outlined above. The zebras of the Quagga Project do not exhibit the idiosyncratic call of the quagga, they do not have the reverse sexual dimorphism and the (possibly) shorter mane. Apart from the phenotype, there are genetic differences as well. The quagga has unique mitochondrial haplotypes and does not share any haplotypes with the plains zebra [1], indicating reproductive isolation for a considerable time span. Thus, the quagga was also genetically distinct and the zebras of the Quagga Project will necessarily differ also genetically. 

Another problem is that the zebras of the quagga project only have a raw similarity to the quagga based on the coat colouration. While the amount of stripe reduction that was achieved is impressive, the animals lack the deep brown base colour on the trunk and also the stripe pattern is different: the white space between the stripes on the face and neck is rather white because the stripes are comparably thin, sometimes with faint brown stripes between the black stripes, while in all the preserved quagga skins the stripes on face and neck are rather broad, with a narrow white space between them and no faint stripes between the solid stripes. Therefore, the only similarity between the zebras of the quagga project is that the stripes are reduced on trunk and legs. Everything else is different. That is why I wrote the article Please don’t call it quagga in 2015, suggesting that these zebras should neither be called “quagga” nor “Rau quagga”. 

Perhaps the quagga project is not even a “breeding-back” project in the strict sense, since it does not work with living descendants of the quagga but merely more or less related animals of a completely different subspecies. 

Nevertheless, I am happy that there is the Quagga Project. While they cannot recreate the quagga, they have produced animals that could be useful for outbreeding a genetically resurrected quagga, for the case that the quagga one day will be recreated by using genome editing. 

 

Literature 

 

[1] Hofreiter et al.: A rapid loss of stripes: the evolutionary history of the extinct quagga. 2005. 

[2] Heywood: Sexual dimorphism of body size in taxidermy specimens of Equus quagga quagga Boddeart (Equidae).2019.