The Tiburon Island population of desert bighorn sheep has increased in size
from 20 founders in 1975 to approximately 650 in 1999. This population is
now the only population being used as the source stack for transplantations
throughout northern Mexico. To evaluate the genetic variation in this popu
lation we examined 10 microsatellite loci and a major histocompatibility co
mplex (MHC) locus. The genetic variation was significantly less than found
in other populations of the same subspecies in Arizona. Using a model that
takes into account the effects of genetic drift on genetic distance, most o
f the genetic distance observed between the Tiburon population and Arizona
samples could be explained. Because of the low genetic variation found in t
he Tiburon population, it is suggested that the Tiburon population should b
e supplemented with additional unrelated animals or that the transplant pop
ulations should be supplemented with unrelated animals.