Population subdivision among desert bighorn sheep (Ovis canadensis) ewes revealed by mitochondrial DNA analysis

We used behavioural observations and mitochondrial DNA (mtDNA) sequence ana lysis to examine demographic and genetic structure within and among home-ra nge groups of desert bighorn sheep (Ovis canadensis) ewes in the Peninsular Ranges of southern California, USA. We identified substantial genetic vari ation in the first 515 bp of the mtDNA control region and determined that s even haplotypes were distributed in a non-random fashion among these ewe su bpopulations. Although a significant (P < 0.01) amount of mtDNA variation ( 33%) was partitioned among home-range groups, we did not find strong eviden ce for matrilineal substructuring within these groups. Based on analyses of molecular variance, and comparisons of behavioural associations and distan ces between centres of activity, we concluded that within a given home-rang e group, bighorn sheep ewes generally associate with other ewes based on th eir availability rather than their matrilineal relationships. Our results a lso supported the conclusion that multiple ewe subpopulations exist within the Peninsular Ranges, and that these subpopulations are the most basic dem ographic and genetic units.