Molecular and morphological evidence on the phylogeny of the Elephantidae

The African and Asian elephants and the mammoth diverged ca. 4-6 million ye ars ago and their phylogenetic relationship has been controversial. Morphol ogical studies have suggested a mammoth-Asian elephant relationship, while molecular studies have produced conflicting results. We obtained cytochrome b sequences of up to 545 base pairs from five mammoths, 14 Asian and eight African elephants. A high degree of polymorphism is detected within specie s. With a dugong sequence used as the outgroup, parsimony and maximum-likel ihood analyses support a mammoth-African elephant clade. As the dugong is a very distant outgroup, we employ likelihood analysis to root the tree with a molecular clock, and use bootstrap and Bayesian analyses to quantify the relative support for different topologies. The analyses support the mammot h-African elephant relationship, although other trees cannot be rejected. A ncestral polymorphisms may have resulted in gene trees differing from the s pecies phylogeny. Examination of morphological data, especially from primit ive fossil members, indicates that some supposed synapomorphies between the mammoth and Asian elephant are variable, others convergent or autapomorpho us. A mammoth-African elephant relationship is not excluded. Our results hi ghlight the need, in both morphological and molecular phylogenetics, for mu ltiple markers and close attention to within-taxon variation and outgroup s election.