Complete mitochondrial genomes of Bos taurus and Bos indicus provide new insights into intraspecies variation, taxonomy and domestication

The taurine and zebuine cattle breeds comprise the majority of the
world cattle population but their taxonomic status is still
controversial. The two forms of cattle are currently classified as
Bos taurus and Bos indicus species and are differentiated primarily
by the presence or absence of a hump. However, these two species
hybridize readily, producing fully fertile offspring. We have
determined and analyzed complete B. taurus and B. indicus
mitochondrial genome sequences to investigate the extent of
sequence divergences and to study their taxonomic status by
molecular dating. The sequences encompassed 16,338 and 16,339
nucleotides, respectively, and differed at 237 positions. Estimated
divergence times indicated that the two cattle lineages separated
1.7-2.0 million years ago. Combined phylogenetic analyses of 18 new
and 130 previously reported extant B. taurus and B. indicus control
region sequences with data from 32 archaeological specimens of the
extinct wild aurochs (Bos primigenius) identified four major
maternal lineages. B. primigenius haplotypes were present in all
but the B. indicus lineage, and one B. taurus sequence clustered
with B. primigenius P haplotypes that were not previously linked
with domestic cattle. The B. indicus cluster and a recently
reported new B. primigenius haplotype that represents a new lineage
were approximately equidistant from the B. taurus cluster. These
data suggest domestications from several differentiated populations
of B. primigenius and a subspecies status for taurine (B.
primigenius taurus) and zebuine (B. primigenius indicus) cattle.
Copyright (C) 2008 S. Karger AG, Basel.