Using Mitochondrial DNA (mtDNA) to Investigate the Genetic Population Structure of Harbor Seals (Phoca vitulina) in Washington…

Harbor seals (Phoca vitulina) are the most abundant marine mammal in Washington State waters and consume many species of fish that hold significant cultural, economic, and ecological importance for humans. Hence, the management of harbor seal populations is of interest to many diverse communities throughout the state. Here, we describe the genetic population structure of harbor seals using mtDNA gathered from subsamples of male and female stranded harbor seals across varying ages and geographic locations. We employ Sanger Sequencing of the mtDNA D-loop to gather maternal genetic information and have found evidence of detectable genetic diversity in the mitochondrial genome of harbor seals from different locations. When analyzing the haplotype composition of certain regions, we found that while there are no fixed regional haplotype differences, there are differences in haplotype proportions per region and haplotypes unique to certain regions. This indicates that female gene flow does not occur freely throughout the entire sampling region, but rather stays within adjacent regions. Comparing our results with a parallel study by MS-Biology candidate Alexandrea Otto on nuclear genetic variation representing male gene flow using the same samples, we found that both male and female gene flow tend to stay within nearby regions. While previous studies have noted philopatric behavior in female harbor seals and more transient behavior in male harbor seals, our research indicates that males are not mating when outside of their regions, but rather are using these long-distance trips for foraging or other purposes. This information will ultimately be used to inform harbor seal population management efforts in Washington State.