Phylogeny and zoogeography of six squirrel species of the genus Sciurus (Mammalia, rodentia), inferred from cytochrome b gene sequences

To investigate the phylogenetic relationships between the New World Sciurus and the Old World Sciurus and their biogeographic history, the partial mit ochondrial cytochrome b gene sequences (1,040 base pairs) were analyzed on six Sciurus species: S. aberti, S. carolinensis, S. lis, S. niger, S. stram ineus, and S. vulgaris. Phylogenetic trees (maximum parsimony, neighbor-joi ning, and maximum likelihood methods) commonly showed two groups with high bootstrap values (73-100%): one consisting of the New World Sciurus and the other consisting of the Old World Sciurus. Genetic distances among the New World Sciurus species were remarkably larger than that between two Sciurus species of the Old World, suggesting the earlier radiation of the New Worl d Sciurus than the Old World Sciurus.