The amount of genetic variation in two natural populations of Queensland koalas (Phascolarctos
cinereus adustus) was assessed by analysis of mitochondrial DNA. Levels and any adverse effects of
inbreeding (inbreeding depression) were estimated from the pedigree of a well-characterised captive
colony. Genetic diversity of mitochondrial DNA was found to be exceedingly low both within and
between the two populations, but the variation detected was found to be strongly structured geographically.
Inbreeding levels in the captive colony were moderate to high yet the only apparent
evidence of inbreeding depression was a male-biased sex ratio. There was no evidence for decreased
juvenile survivorship or growth rate with inbreeding. Because of the limited data it would be premature
to conclude that koalas are relatively resistant to the effects of inbreeding. However, we suggest the
hypothesis that koalas have a history of small population size, resulting in reduced susceptibility to
inbreeding depression.
Mitochondrial DNA analyses revealed low genetic diversity in the endangered Indian wild ass Equus hemionus khur
