13 - Genetic population structure in desert bighorn sheep: implications for conservation in Arizona

Summary

ABSTRACT

Bighorn sheep populations have been reduced in both distribution and abundance during the last 200 years, mainly due to the introduction of new infectious disease carried by domestic livestock. Translocation efforts to historical habitat have been quite successful, but the expense of such projects, and the importance of selecting appropriate source stock, make an understanding of genetic variation within and among populations very important. Two subspecies of desert bighorn sheep are currently recognized in Arizona: Ovis canadensis nelsoni in northern Arizona and O. c. mexicana in southern Arizona. From our study often microsatellite loci it was found that: (l) all populations have high amounts of genetic variation, (2) populations within northern Arizona and within southern Arizona are genetically similar, (3) northern Arizona populations are genetically different from southern Arizona populations and (4) genetic distance appears to be a function of geographic distance over short distances (< 300 km) in the south-western region of the United States.

INTRODUCTION

Over the past 200 years, bighorn sheep (Ovis canadensis spp.) populations have been greatly reduced in both distribution and abundance. Buechner (1960) reviewed the status of this species throughout its range and reported a reduction of nearly 98% (approximately 25000 animals left). Disease transmission from livestock is considered the most important factor contributing to the population decrease although overhunting, habitat loss and other factors have also been implicated. To rebuild populations, there has been reintroduction into the historic range and augmentation of existing populations.