Microsatellite analysis of population structure in the endangered Hawaiianmonk seal

The endangered Hawaiian monk seal breeds at six locations in the northweste rn Hawaiian Islands. To determine whether significant genetic differentiati on exists among these sites, we used microsatellite loci to examine the mon k seal population structure at the five largest breeding colonies. Of 27 lo ci isolated from other seal species, only 3 were polymorphic in an initial screening of one individual from each breeding site. Only two alleles were found at each of these 3 loci in samples of 46-108 individuals. This extrem ely low variation is consistent with other measures of genetic variability in this species and is probably the result of a recent severe population bo ttleneck, combined with a long-term history of small population sizes. Alth ough the smallest monk seal subpopulation in this study (Kure Atoll) showed some evidence of heterozygote deficit, possibly indicative of inbreeding, the next smallest (Pearl and Hermes Reef) had an apparent excess of heteroz ygous individuals. Genetic differentiation was detected between the two sub populations at extreme ends of the range (Kure and French Frigate Shoals). This trend was significant only at the microsatellite locus for which we ha d the largest sample size (Hg6.3: R-ST = 0.206, p = 0.002; allelic goodness of fit G(h) = 15.412, p < 0.005). French Frigate Shoals is the source popu lation for translocated animals that have been released primarily at Kure A toll. Differentiation between these sites consisted of allele frequency dif ferences (with the same allele predominant in each location at all three lo ci), rather than the preservation of alternative alleles. Although the tran slocations have had positive demographic effects, we recommend continued ge netic monitoring of both the source and recipient populations because trans located individuals are now entering the breeding population.