LOW GENETIC-VARIABILITY IN THE HAWAIIAN MONK SEAL

The Hawaiian monk seal (Monachus schauinslandi) is a critically endang ered species that has failed to recover from human exploitation despit e decades of protection and ongoing management efforts designed to inc rease population growth. The seals breed at five principal locations i n the northwestern Hawaiian islands, and inter-island migration is lim ited. Genetic variation in this species is expected to be low due to a recent population bottleneck and probable inbreeding within small sub populations. To test the hypothesis that small population size and str ong site fidelity has led to low within-island genetic variability and significant between-island differentiation, we used two independent a pproaches to quantify genetic variation both within and among the prin cipal subpopulations. Mitochondrial control region and tRNA gene seque nces (359 base pairs) were obtained from 50 seals and revealed very lo w genetic diversity (0.6% variable sites), with no evidence of subpopu lation differentiation. Multilocus DNA fingerprints from 22 individual s also indicated low genetic variation in at least some subpopulations (band-sharing values for ''unrelated'' seals from the same island ran ged from 49 to 73%). This method also provided preliminary evidence of population subdivision (F'(st) estimates of 0.20 and 0.13 for two adj acent island pairs). Translocations of seals among islands may therefo re have the potential to relieve local inbreeding and possibly to redu ce the total amount of variation preserved in the population. Genetic variation is only one of many factors that determine the ability of an endangered species to recover. Maintenance of existing genetic divers ity, however, remains an important priority for conservation programs because of the possibility of increased disease resistance in more var iable populations and the chance that inbreeding depression may only b e manifest under adverse environmental conditions.