A rapid loss of stripes: the evolutionary history of the extinct quagga

Abstract

Twenty years ago, the field of ancient DNA was launched with the publication of two short mitochondrial (mt) DNA sequences from a single quagga (Equus quagga) museum skin, an extinct South African equid (Higuchi et al. 1984 Nature312, 282-284). This was the first extinct species from which genetic information was retrieved. The DNA sequences of the quagga showed that it was more closely related to zebras than to horses. However, quagga evolutionary history is far from clear. We have isolated DNA from eight quaggas and a plains zebra (subspecies or phenotype Equus burchelli burchelli). We show that the quagga displayed little genetic diversity and very recently diverged from the plains zebra, probably during the penultimate glacial maximum. This emphasizes the importance of Pleistocene climate changes for phylogeographic patterns in African as well as Holarctic fauna.

Figure 1

The morphological variability within living plains zebras and the extinct quagga. Upper row, left: mare ‘Tracy’ from the quagga rebreeding programme, probably the most quagga-like living plains zebra; middle: a plains zebra from the Etosha area; right: E. b. boehmi, a subspecies with very pronounced striping and no brown coloration or shadow-stripes in the white parts. Lower row, left: Munich quagga, one of the specimens with the least striping; right: Tring quagga, one of the unquestioned quagga specimens with the most pronounced striping.

Figure 2

Phylogeny of all zebra species and quagga. One of 64 most parsimonious trees (136 steps). Node support is indicated when above 50% for parsimony (above branch) and neighbour-joining bootstrap and maximum likelihood from a long run of MrBayes (below branch). GenBank numbers for sequences are from Oakenfull et al. (2000).