Title: Microsatellite and allozyme analyses reveal few genetic differences among spatially distinct aggregations of geoduck clams
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ABSTRACT The genetic population structure of geoduck clams (Panopea abrupta) in inland waters of Washington may affect fishery management and aquacultural practices involving this species. To investigate genetic differentiation in geoduck clams, samples were collected from 16 Washington State sites located in the five Puget Sound sub basins, southern Georgia Strait, and the Strait of Juan de Fuca. A collection from Clarence Strait in SE Alaska was included as an outgroup. Individuals were genotyped at 11 allozyme and 7 microsatellite loci. There was little differentiation overall, but the Freshwater Bay collection in the Strait of Juan de Fuca was differentiated from others at both microsatellite and allozyme loci. For both marker classes, there was no evidence of significant correlation between genetic and geographic distance measures. In contrast to the microsatellite loci, the allozyme loci were in Hardy-Weinberg Equilibrium (HWE). Deviations from HWE expectations at microsatellite loci were interpreted as being primarily due to primer-site sequence variation rather than population level processes such as inbreeding. KEY WORDS: Panopea abrupta, geoduck, population genetics, larval dispersal INTRODUCTION Understanding the extent of gene flow provides insight into the demographic dynamics among natural populations. Generally, gene flow is correlated with dispersal ability in many organisms (Bohonak 1999), including many marine fishes and shellfishes (reviewed in Shaklee & Bentzen 1998). In sedentary marine bivalves, dispersal and gene flow occur only during the pelagic larval phase. Gene flow and larval dispersal may be correlated with spatial distribution in marine mollusks (Johnson et al. 2001); many investigators have failed to falsify the null hypothesis of panmixia at broad geographic scales in a variety of broadcast spawning marine species with pelagic larvae (e.g., Crassostrea virginica [McDonald et al. 1996]; Littorina striata, [De Wolf et al. 2000]; Mytilus galloprovincialis [Skalamera et al. 1999]). Nevertheless, some studies have demonstrated genetic structuring in a variety of marine invertebrate species with pelagic larvae (e.g., the American oyster, Crassostrea virginica [Reeb & Avise 1990]; Ostrea edulis [Launey et al. 2002]; the sea urchins Strongylocentrotus purpuratus [Edmands et al. 1996] and S. franciscanus [Moberg & Burton 2000]; and black abalone Haliotis cracherodii [Harem & Burton 2000]). Examples of genetic differentiation on smaller geographic scales include the limpet Siphonaria jeanae (Johnson & Black 1984), the oyster Crassostrea virginica (Buroker 1983, [King et al. 1994]), cockles Cerastoderma glaucum (Mariani et al. 2002), and Mytilus edulis (Ridgway 2001). Most population genetic studies of marine invertebrates have focused on populations that are distributed along open coasts or island populations with discontinuous distributions separated by deep oceanic water. However, Parsons (1996) demonstrated significant genetic subdivision (9-locus [F.sub.ST] = 0.16) over an area of only 75 [km.sup.2] in the intertidal gastropod, Austrocochlea constricta. Limited water movement in the area studied may have caused localized recruitment, resulting in the detected population differentiation (Parsons 1996). The complex hydrology and bathymetry of Puget Sound in Washington State suggests the potential for restricted dispersal and population subdivision of marine invertebrates in the region. Puget Sound is a fjord-like estuarine system that is highly subdivided by...
Source Citation (MLA 8 th Edition)
Vadopalas, Brent, et al. "Microsatellite and allozyme analyses reveal few genetic differences among spatially distinct aggregations of geoduck clams." Journal of Shellfish Research, vol. 23, no. 3, 2004, p. 693+. Academic OneFile, Accessed 25 June 2018.

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