Microsatellite DNA Variation and the Evolution, Domestication and Phylogeography of Taurine and Zebu Cattle (<i>Bos taurus</i> and <i>Bos indicus</i>)

TLDR

Genetic variation at 20 microsatellite loci was surveyed to determine the evolutionary relationships and molecular biogeography of 20 different cattle populations from Africa, Europe and Asia. The study surveyed 20 microsatellite loci across 20 cattle populations and used a bison outgroup molecular clock to estimate a 610,000–850,000‑year divergence between taurine and zebu cattle. Phylogenetic and multivariate analyses revealed a clear separation between taurine and zebu cattle, estimated divergence of 610,000–850,000 years, distinct allele distributions at 10 loci, and a male‑mediated introgression pattern that threatens disease‑tolerant West African taurine populations.

Abstract

Genetic variation at 20 microsatellite loci was surveyed to determine the evolutionary relationships and molecular biogeography of 20 different cattle populations from Africa, Europe and Asia. Phylogenetic reconstruction and multivariate analysis highlighted a marked distinction between humpless (taurine) and humped (zebu) cattle, providing strong support for a separate origin for domesticated zebu cattle. A molecular clock calculation using bison (Bison sp.) as an outgroup gave an estimated divergence time between the two subspecies of 610,000-850,000 years. Substantial differences in the distribution of alleles at 10 of these loci were observed between zebu and taurine cattle. These markers subsequently proved very useful for investigations of gene flow and admixture in African populations. When these data were considered in conjunction with previous mitochondrial and Y chromosomal studies, a distinctive male-mediated pattern of zebu genetic introgression was revealed. The introgression of zebu-specific alleles in African cattle afforded a high resolution perspective on the hybrid nature of African cattle populations and also suggested that certain West African populations of valuable disease-tolerant taurine cattle are under threat of genetic absorption by migrating zebu herds.