Mitochondrial DNA sequence analysis of the Mexican Creole sheep (Ovis aries) reveals a narrow Iberian maternal origin.

The Creole sheep in America is supposed to have originated specifically from the Iberian Peninsula and introduced by the Spaniards during the colonization. However, it is not clear their genetic relationship with Iberian breeds. The genetic origin and diversity of the Mexican Creole sheep (MCS) were investigated by mitochondrial DNA control region nucleotide sequences. DNA sequence from 33 MCS samples from three regions of México revealed 21 different haplotypes. Phylogenetic analysis including European and Iberian sheep haplotypes showed that the MCS population belongs to a differentiated and defined genetic lineage. This finding suggests that the MCS populations may be the result of a founder effect originating from a discrete Iberian population. MCS haplotypes were related to haplotypes found in the Churro Trunk and the Entrefino Trunk groups of Iberian breeds, supporting historical reports. In the Mexican genetic branch, there were also haplotypes reported from Lacaune and Awassi sheep breeds. Although it is uncertain whether a particular breed was involved as a founder of the MCS, these populations have a common phylogenetic origin.