A new study of the genetics of African elephants shows that forest dwellers differ so much from those roaming the savannas that the two may be separate species. And that may not be the end of the story.
The traditional view lumped African elephants into one species located in a genus different from that of Asian elephants. Previous studies of body parts and some elephant DNA raised the possibility that African elephants should be divided, explain Alfred L. Roca of the National Cancer Institute’s genetics lab in Frederick, Md., and his colleagues. They report in the Aug. 22 Science that their genetic analysis of elephants in 21 populations supports the split.
The elephants in Africa’s tropical forests don’t reach the size of savanna inhabitants. The forest elephants also grow straighter, thinner tusks and rounded ears instead of pointed ones. Joseph P. Dudley, now of the University of Alaska, Fairbanks, and his colleagues found distinctions between the two groups in a 1993 study of 295 skulls in museum collections.
The team reporting the new research, particularly Nicholas Georgiadis of the Mpala Research Center in Kenya, spent years collecting tissue samples from elephants across Africa. In the final comparisons of DNA from cell nuclei, the forest and savanna elephants fell into distinct groups. The elephants’ forest or savanna origins accounted for more than 90 percent of the genetic differences that showed up.
Savanna and forest elephants interbreed occasionally though Roca’s group found little evidence for recent mixing. However, theorists are no longer inclined to declare populations to be the same species just because they mingle and mate.
A split between forest and savanna elephants may not be the only change looming in the family tree, according to Lori Eggert of the Smithsonian Institution in Washington, D.C. Her preliminary results suggest that West African elephants not included in the new study are genetically very distinct.