A phylogeny of the bears (Ursidae) inferred from complete sequences of three mitochondrial genes.

Full Abstract

Complete sequences of DNA are described for the cytochrome b tRNA(Thr) and tRNA(Pro) genes of mitochondria of four extant species of ursids and compared to sequences of four other species of ursids previously studied by us. Phylogenetic analyses indicate that the giant panda and the spectacled bear are the basal taxa of the ursid radiation. The ursines, a group which includes the sun bear, sloth bear, American black bear, Asiatic black bear, brown bear, and polar bear, experienced a rapid radiation during the mid Pliocene to early Pleistocene. The Asiatic black bear and American black bear are sister taxa. The brown bear and polar bear are the most recently derived of the ursines, with the polar bear originating from within a clade of brown bears during the Pleistocene. This paraphyletic association suggests that the rate of morphological evolution may be accelerated relative to that of molecular evolution when a new ecological niche is occupied. Calibration of the corrected average number of nucleotide differences per site with the fossil record indicates that transitions at third positions of codons in the ursid cytochrome b gene occur at a rate of approximately 6% per million years, which is considerably slower than comparable values reported for other species of mammal.

Author information

Author/s: Talbot, S L (SL); Shields, G F (GF);

Affiliation: Institute of Arctic Biology, University of Alaska Fairbanks, Alaska 99775-7000, USA.

Journal and publication information

Publication Type: Comparative Study; Journal Article; Research Support, Non-U.S. Gov't

Journal: Molecular phylogenetics and evolution (Mol Phylogenet Evol), published in UNITED STATES. (Language: eng)

Reference: 1996-Jun; vol 5 (issue 3) : pp 567-75

Dates: Created 1996/11/08; Completed 1996/11/08; Revised 2006/11/15;

PMID: 8744769, status: MEDLINE (last retrieval date: 2/18/2009, IMS Date: )

Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.

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