The complete mitochondrial genome of Tupaia belangeri and the phylogeneticaffiliation of Scandentia to other eutherian orders

The complete mitochondrial genome of Tupaia belangeri, a representative of the eutherian order Scandentia, was determined and compared with full-lengt h mitochondrial sequences of other eutherian orders described to date. The complete mitochondrial genome is 16,754 nt in length, with no obvious devia tion from the general organization of the mammalian mitochondrial genome. T hus, features such as start codon usage, incomplete stop codons, and overla pping coding regions, as well as the presence of tandem repeats in the cont rol region, are within the range of mammalian mitochondrial (mt) DNA variat ion. To address the question of a possible close phylogenetic relationship between primates and Tupaia, the evolutionary affinities among primates, Tu paia and bats as representatives of the Archonta superorder, ferungulates, guinea pigs, armadillos, rats, mice, and hedgehogs were examined on the bas is of the complete mitochondrial DNA sequences. The opossum sequence was us ed as an outgroup. The trees, estimated from 12 concatenated genes encoded on the mitochondrial I-I-strand, add further molecular evidence against an Archonta monophyly. With the new data described in this paper, most of both the mitochondrial and the nuclear data point away from Scandentia as the c losest extant relatives to primates. Instead, the complete mitochondrial da ta support a clustering of Scandentia with Lagomorpha connecting to the bra nch leading to ferungulates. This closer phylogenetic relationship of Tupai a to rabbits than to primates first received support from several analyses of nuclear and partial mitochondrial DNA data sets. Given that short sequen ces are of limited use in determining deep mammalian relationships, the par tial mitochondrial data available to date support this hypothesis only tent atively. Our complete mitochondrial genome data therefore add considerably more evidence in support of this hypothesis.