The Takin And Muskox: Relationship musk not be takin for granted
Pamela Groves and R.G. White
Institute of Arctic Biology
Supporting Agencies: Boone and Crockett Club; the Explorers' Club; the Shaanxi Institute of Zoology; a TOTE Dissertation Year Fellowship and a University of Alaska Fairbanks Foundation Scholarship.
The relationships of the takin (Budorcas taxicolor) and muskox (Ovibos moschatus) have been speculated upon since these species were introduced into scientific literature. Early speculation related the takin to the "gnoo" or wildebeest (Connochaetes taurinus)(Hodgson, 1850) and the muskox to the buffalo (Bison bison)(Allen, 1913). Subsequent studies placed the muskox within the subfamily Caprinae (Simpson, 1945; Moody, 1958). The two species were proposed to be close relatives based on traditional phylogenetic characteristics (Allen, 1913; Simpson, 1945), which may not reconstruct phylogeny as accurately as molecular characteristics accessible through modern techniques. I used sequences of the mitochondrial cytochrome b gene to test the hypothesis that the takin and muskox are sister taxa. My data reject this hypothesis and establish new phylogenetic relationships within the Caprinae.
Comparison of cytochrome b
sequences of the takin and muskox has provided a new perspective on the relationship
of these species. Based on the assumption of a molecular clock, the two species have been
separated over nine MY, whereas each may have diverged from another species less than five
million years ago (MYA). The paucity of Caprinae fossils has prevented calibration of the
rate of evolution for this subfamily, but the relative times can be considered valid.
Clearly, similarities between the species cannot be attributed to a common phylogeny and
shared genetic heritage, but demonstrate the force of natural selection and convergent
evolution in selecting for development of similar characteristics in separate lineages.
These characteristics must be plastic and able to change within the constraints of the
genetic heritage. Advantages of large body size and horns effective as predator defense
are significant enough that these combined characteristics can be expected to evolve
independently as lineages adapt to different environments. Because of the
interrelationship of morphological and ecological characteristics, a suite of similarities
can develop between species that is not reflective of close genetic ancestry.
Literature cited
Allen, J. 1913. Ontogenetic and other variations in muskoxen, with a systematic review of the muskox group, recent and extinct. Mem. Amer. Mus. Nat. Hist., New Ser. 1: 101-226.
Hodgson, B.H. 1850. On the takin of the eastern Himalaya. J. Asiatic Soc.19: 65-75.
Moody, P. 1958. Serological evidence on the relationships of the musk ox. J. Mamm. 39: 554-559.
Simpson, G.G. 1945. The principles of classification and a classification of mammals Bull.Amer.Mus.Nat.Hist.85: 1-350.
