Recent Population Demography of Peninsular Bighorn Sheep Derived from Microsatellite Allele Spectrum Analysis

New computational methods for analyzing the pattern of mutations across genetic loci that display simple sequence repeat motifs (commonly called microsatellites) are providing detailed insights into changes of population size over time. Knowledge of the demographic history of a population is a crucial component in assessing its level of vulnerability according to International Union for the Conservation of Nature (IUCN) standards and provides significant new perspectives regarding anthroprogenic and environmental impacts such as epidemics, volcanic explosions, hurricanes, overall climate change, and predation (including hunting regimes).

The Peninsular bighorn sheep, resident from the San Jacinto Mountains to the U.S.– Mexico border, is a federally listed endangered species whose recovery will depend on the maintenance of metapopulation segments across the historical habitat. Carrying capacity of the Peninsular ranges is largely unknown and historical population efforts prior to the mid 1970s are imprecise. Achieving improved estimates of historical population sizes and the genetic fragmentation of Peninsular bighorn sheep subpopulations within the Peninsular ranges would contribute to highly desired refinements of the recovery plan for this species.

This project will use available DNA microsatellite data that utilizes previously published primer sequences and will, as well, generate new data on microsatellite variation in Peninsular bighorn sheep. The combined data sets will be subjected to statistical analyses, such as the Bayesian approaches that have found recent application in landmark studies for other endangered species (such as Bornean orangutans) to estimate population sizes of Peninsular bighorn sheep through time.