Dec 26, 2010

African Elephants do not Belong to the Same Species

For some time there has been considerable controversy regarding the phylogenetic relationship among the surviving species of elephants and their extinct relatives: the mammoths and mastodons. After an exhaustive study led by Dr. David Reich of Harvard Medical School in Boston, convincing results regarding the genetic proximity between these animals have been found. The study explains that African elephants belong to two distinct species and not two populations of the same species, as was believed until now.

African savanna elephants are much larger than African forest elephants and their genetic divergence occurred between 2.6 and 5.6 million years ago. This separation is comparable to that of the current Asian elephants (Elephas maximus) and their extinct cousins, the mammoths. The social nature of these animals may have been the cause behind the debate about the relationship among elephant species: the females are relatively more stationary and live in a matriarchal society where the only guests are male nomads. According to the authors, savanna males may have mated with females of forest and raised viable offspring since hybridization can occur between different but related species; however, the genetic exchange has not been sufficient to generate a single species.

The controversy arose because earlier studies had used mitochondrial DNA for their analysis, which is only a reflection of the maternal line; for this reason, the contribution of the father had been overlooked. On the contrary, the recent article by Dr. Reich, et al. published in PLoS Biology, managed to overcome the methodological problems of obtaining sufficient genetic material from extinct animals. The group's technique consisted in analyzing nuclear DNA, which is a genetic mix of both parents and a lot more extensive than mitochondrial DNA; thus producing more reliable results.
Outside the scientific relevance of the study, the results could have important implications for policy-makers in order to protect these species more effectively. According to the authors, the African forest elephant males could use much more help from conservation programs, rather than their robust competitors in the savannah.

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