Publication Date

Summer 2013

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Biological Sciences

Advisor

Leslee Parr

Keywords

Cancer magister, COI, Conservation, Ecology, Genetics, Larval dispersal

Subject Areas

Biology; Conservation biology; Genetics

Abstract

Spatial and temporal genetic variation was assessed using mitochondrial DNA from adult and megalopae of Dungeness crabs, Cancer magister, from Fraser Delta in British Columbia, Washington, Oregon, and California. Megalopae were continuously sampled using light traps in one location, Coos Bay, Oregon, and compared with adults sampled across the species' range. While small-scale spatial and temporal variation were evident, there was no significant fit to the Isolation-by-Distance model when considering adult and larvae populations sampled over a coastal length of ~1700 km (Mantel r = 0.059, p = 0.289). Smaller bays showed higher genetic diversity than larger bays, contrary to typical expectations. MtDNA diversity measures (assessed by canonical correlation analysis) were correlated with bay size and depth, suggesting that hydrological patterns or fishing harvests in local areas (or a combination of both) influenced the observed genetic signature. The Dungeness crab ancestral population likely went through a historic population expansion associated with recent glacial relaxation, as evidenced by mismatch distributions and predominance of singleton haplotypes. In larval samples, we commonly observed numerous individuals of a haplotype, which suggests that families of larvae remain aggregated during dispersal. Sampled offspring revealed a low fraction of the adult gene pool (in accordance with the Hedgecock effect), yet high variability in recruitment over time. A realized long distance dispersal of larvae and the additive effects of recruitment from different sources over time may have prevented significant genetic differentiation within the C. magister range.

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