This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American
Imagine living underground for six years waiting for water. That might seem like a challenge, but it's just a normal part of the life cycle for the African helmeted terrapin. These common side-necked turtles, which bend their necks to the side until their heads are protected by one leg and an overhang of their shell, live throughout Africa and part of the Arabian Peninsula. They have also been the subject of an awful lot of scientific disagreement over the centuries. Biologists have named and renamed and reclassified the 20- to 30-centimeter turtles more than a dozen times since 1778, the year they were first scientifically described. Some researchers declared the terrapins as multiple species or various subspecies. Most recently biologists have declared the terrapins to be just a single species, making it the widest ranging reptile in all of Africa.
Well, now it's time to do it all over again. According to genetic research published May 15 in Zootaxa (pdf), African helmeted terrapins are not one wide-ranging, common species (what's currently known as Pelomedusa subrufa) but at least 10 separate species, maybe even more. Many of these "new" species, according to lead author Uwe Fritz of the Senckenberg Research Institute in Germany, have extremely limited distributions and are probably endangered. In particular, the terrapins on the Arabian Peninsula suffer from a severe shortage of available water and may be threatened with extinction.
Fritz and his colleagues examined 350 terrapins from across their range and conducted genetic tests on 200 of them. In addition to modern specimens, they tracked down many of the decades- or centuries-old museum samples from the years in which the various since-dismissed species and subspecies were first described. One of the first specimens described in Fritz’s paper was collected way back in 1788, although it was too old and contaminated by mold to allow collection of usable genetic material.
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The genetic research actually gives cause for reinstating a few of the previously discarded taxonomic classifications for these turtles. For example, the terrapins in Benin, Burkina Faso, Niger and Nigeria could end up with the original species name from when they were first described in 1812, Emys olivacea. Fritz’s team also conclusively ruled out many other old classifications, even going as far as to prove that some samples were not collected in the areas in which the original researchers said they did. In addition to the Zootaxa paper, the researchers have also made all of their genetic testing data available online.
All told, six of the 10 genetic lineages described in the paper are brand-new and will need to be fully reclassified. Hopefully the taxonomic arguments will be shorter-lived this time around.
Photo: The African helmeted terrapin of Namibia, the only species to retain the original Pelomedusa subrufa taxonomic name. Photo by A. Schleicher, courtesy of Senckenberg Research Institute