Genetics

• Microsatellite DNA and mitochondrial DNA variation in polar bears (Ursus maritimus) from the Beaufort and Chukchi seas, Alaska
• Establishing paternity with genetic fingerprinting

Microsatellite DNA and mitochondrial DNA variation in polar bears (Ursus maritimus) from the Beaufort and Chukchi seas, Alaska

Radiotelemetry data have shown that polar bears (Ursus maritimus Phipps, 1774) occur in separate subpopulations in the Chukchi Sea and the southern Beaufort Sea. However, segregation is not absolute, and there is overlap of ranges of animals in each subpopulation. We used genetic variation at eight microsatellite DNA loci and mitochondrial DNA (mtDNA) to further assess the degree of spatial structure of polar bears from the Chukchi and southern Beaufort seas. Microsatellite allele frequencies and mtDNA haplotype frequencies of bears from the southern Beaufort and Chukchi seas did not differ significantly. Lack of differentiation at both maternally inherited mtDNA and bi-parentally inherited microsatellite loci suggests that gene flow between the two areas is mediated by both sexes. The genetic data indicate that polar bears in the southern Beaufort and Chukchi seas compose one interbreeding population. However, there is considerable fidelity to ranges in each area, particularly by adult females. The combined genetic and movement data suggest that polar bears could be managed as Beaufort Sea and Chukchi Sea subpopulations of a combined southern Beaufort Sea and Chukchi Sea population.

Establishing paternity with genetic fingerprinting

Polar bears are the most mobile of all quadrupeds, their movements are more variable than most other bears, and surprisingly, male polar bears appear to be no more mobile, in some locales and at some times of the year, than female polar bears. This suggests that a breeding pattern different from that in other bears is possible.

To explore breeding patterns in polar bears, we extracted DNA from blood and tissue samples amplified the DNA using PCR, and used acrylamide gel electrophoresis to sequence the samples and identify specific alleles. Scores obtained were used to determine how closely individual polar bears might be related. Mother-offspring and sibling pairs were known because family groups often are captured together during spring fieldwork. Such physical evidence of paternity is not available because male polar bears accompany females only during breeding.

Collaborating with Matt Cronin, Research Professor, University of Alaska Fairbanks, School of Natural Resources and Agriculture Science, Palmer, Alaska, Palmer Research and Extension Center