Ancient DNA reveals genotypic relationships among Oregon populations of the sea otter (Enhydra lutris)

Abstract

The sea otter has experienced a dramatic population decline caused by intense human harvesting, followed by a century of recovery including relocation efforts to reestablish the species across its former range in the eastern Pacific. Although the otter was historically present along the coast in Oregon, there are currently no populations in this region and reintroduction efforts have failed. We examined the mtDNA genotypes of 16 pre-harvest otter samples from two Oregon locations in an attempt to determine the best genotypic match with extant populations. Our amplifications of a 222 base-pair portion of the control region from otters ranging in age from approximately 175-2000 years revealed four genotypes. The genotypic composition of pre-harvest otter populations appears to match best with those of contemporary populations from California and not from Alaska, where reintroduction stocks are typically derived.

Conservation archaeogenomics: ancient DNA and biodiversity in the Anthropocene

“…In the case of the sea otter (Enhydra lutris), genetic data from microsatellites show dramatic losses in heterozygosity and allelic diversity following the fur trade; however, otter population structure seems consistent through time [27]. Interestingly, mtDNA of archaeological sea otters from Oregon showed that they were more closely related to the least genetically diverse otter population from California, rather than Alaska, the source population for the unsuccessful Oregon otter reintroduction [28]. Studies such as these demonstrate the value of archaeological samples for identifying appropriate source populations for reintroductions.…”

DNA from historical and trophy samples provides insights into white shark population origins and genetic diversity

“…Stringent measures employed in successful ancient/ historical DNA projects (Valentine et al 2008, McMenamin & Hadly 2012 were instigated to eliminate contamination risks. All DNA extractions, including those from teeth, took place in laboratories free of contemporary shark material, and separate tools were designated for use on historical tissue and cleaned with 25% sodium hypochlorite solution between samples.…”

Archaeological Protein Residues: New Data for Conservation Science

“…Pacific Otters-As discussed by Valentine et al (2008), extensive hunting during the eighteenth and nineteenth centuries led to drastic reductions in sea otter (Enhydra lutris) populations in the eastern Pacific Ocean, particularly in Oregon, where they were extirpated. Attempted reintroductions of sea otters to this region have been largely unsuccessful despite more fruitful results in areas to the north, and recent research has provided several important clues as to why the Oregon reintroduction failed.…”

“…Studies of morphological (Wilson et al 1991) and genetic (Valentine et al 2008) variation suggest that there are several distinct genotypes associated with three different subspecies of sea otter: the common sea otter (E. l. lutris), the southern sea otter (E. l. nereis), and the northern sea otter (E. l. kenyoni). In the case of Oregon reintroduction efforts, a population of northern sea otters was transplanted from Alaska.…”

“…In the case of Oregon reintroduction efforts, a population of northern sea otters was transplanted from Alaska. However, examination of the zooarchaeological record via morphometric (Lyman 1988) and DNA (Valentine et al 2008) studies demonstrated that this particular subspecies has never been common in Oregon and that it is likely not well-suited to the unique environmental conditions of the Oregon coast. Instead, the extirpated populations more closely resemble southern sea otters currently living in California.…”