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KeywordsNucleotide Phylogenetic Analysis Genetic Distance National Cancer Institute Single Species
African elephants are often considered to represent a single species, Loxodonta africana, which is distinct from the Asian elephant genus Elephas. In the August 24 Science, Alfred Roca and colleagues from the US National Cancer Institute challenge this assumption by presenting their results of a phylogenetic analysis of African elephants (Science 2001, 293:1473-1477). They collected dart-biopsy samples from almost two hundred free-ranging elephants from 21 populations and sequenced 1732 nucleotides from four nuclear genes. Phylogenetic analysis of these sequences demonstrated that African elephants can be divided into distinct forest and savannah populations. Savannah populations were genetically closer to each other than to any of the forest populations. The genetic distance between forest and savannah elephants was 9.0, which corresponds to 58% of the distance between African and Asian elephant genera. The results suggest that the two African populations split approximately 2.63 million years ago. Roca et al. propose that African elephants should therefore be considered as two species, Loxondonta africana (savannah elephants) and Loxondonta cyclotis(forest elephants).