Thequagga, Equus quagga, a South African relative of horses and zebras,having a front half with zebra-like stripes and a back section like ahorse with no marking, became extinct about 100 years ago. The peltfrom a quagga museum specimen was the subject of tissue sampling thatlaunched the field of ancient DNA analysis.
"Twenty years agothis exact species opened the field of ancient DNA studies on extinctanimals," said one of the authors, Gisella Caccone, senior researchscientist in the Department of Ecology and Evolutionary Biology atYale. "Now, thanks to technological advances in the field, we revisitedthe story and used a population level approach to this question byanalyzing a larger fragment of DNA and multiple specimens."
Inthe past, the quagga has alternatively been described as a species anda subspecies of the Plains zebra.These researchers asked how and whenthe quagga diverged from all the remaining related horses, zebras, andasses. They compared the genetics, coat color and habitats of existingzebras with related extinct species.
The mitochondrial DNAmarkers from 13 museum specimens, including the only skeleton in museumcollections, which is at Yale's Peabody Museum of Natural History,showed that quagga likely diverged from Plains zebra about 120,000 to290,000 years ago during the Ice Age. These results suggest that thequagga descended from a population of plains zebras that becameisolated and the distinct quagga body type and coloring evolved rapidly.
This study reveals that the Ice Age was important not just in Europe and North America, but also in Africa.
"Therapid evolution of coat color in the quagga could be explained bydisrupted gene flow because of geographical isolation, an adaptiveresponse to a drier habitat, or a combination of both of the twoforces," said Caccone.
The research team also includedScott Glaberman at Yale, Jennifer A. Leonard and Robert C. Fleischerfrom the Smithsonian Institute, Michael Hofreiter and Nadin Rohlandfrom the Max Planck Institute for Evolutionary Anthropology.
Citation: Biology Letters (Royal Society of London): (September 22, 2005)
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