VARIATION IN MITOCHONDRIAL-DNA AND PHYLOGENY OF 6 SPECIES OF PIKAS (OCHOTONA)

Phylogenetic relationships of six species of Ochotona were investigate d using mitochondrial DNA (mtDNA) restriction-site analysis. The phylo genetic tree constructed using PAUP was based on 62 phylogenetically i nformative sites with O. erythrotis designated as an outgroup. Two cla des were evident. One contained O. curzoniae, O. huangensis, and O. th ibetana. in the second, O. daurica was a sister taxon of O. cansus. Th e five species appear to come from different maternal lineages. The br anching structure of the tree and sequence divergence confirm that hua ngensis and cansus are distinct species, and that mol-osa is a synonym of O. cansus rather than O. thibetana. Divergence time, estimated fro m genetic distances, indicates that the ancestors of the two maternal lineages diverged ca. 6.5 x 10(6) years ago. O. curzoniae diverged fro m O. huangensis, and O. daurica diverged from O. cansus, at about the same time (ca. 3.4 x 10(6) years ago). These data suggest a period of rapid radiation of the genus Ochotona in China, perhaps during the lat e Pliocene. These calculations correspond roughly to tectonic events a nd environmental changes in China throughout this period, and appear t o be substantiated by the fossil record.