RAPID CLADOGENESIS AMONG THE PECORAN RUMINANTS - EVIDENCE FROM MITOCHONDRIAL-DNA SEQUENCES

We sequenced 2.7 kilobase pairs of contiguous coding mitochondrial DNA from Antilocapra americana (Antilocapridae), Capra hircus (Bovidae), and Tragulus napu (Tragulidae) and compared these to previously published orthologues for other ruminant species. Phylogenetic analysis of these sequences provided no robust patterns of relationship for the four families of pecoran ruminants studied. This finding is consistent with the hypothesis that the pecoran families resulted from a rapid radiation in the Early Miocene to Late Oligocene. This hypothesis is supported by the short internal branch lengths of our most-parsimonious solutions and, more importantly, by the narrow range of interfamilial sequence divergence, suggesting that the radiation may have occurred over a period of 5 million years (about 23-28 million years ago). The importance of using large amounts of conservative sequence data for resolving relationships among members of a rapid radiation is discussed.