Author
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Camara, Mark |
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Submitted to: Aquatic Living Resources
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 3/14/2011 Publication Date: 6/15/2011 Citation: Camara, M.D. 2011. Changes in molecular genetic variation at ALFP loci associated with naturalization and domestication of the Pacific oyster (Crassostrea gigas). Aquatic Living Resources. 24:35-43. Interpretive Summary: The Pacific oyster (Crassostrea gigas) is an important commercial species in the US Pacific Northwest with a history of farming first using wild-caught seed imported directly from the Miyagi region of northern Japan followed by an extended period of seed collection from a few naturalized populations in the US (early 1970s-present) and more recently through large-scale hatchery production of oyster seed (mid 1970s-present). I studied the genetic level consequences of each of introduction to the US and using molecular genetic markers. All but one of the naturalized populations are genetically more similar to native populations from the Ariake Sea (Midori River) in southern Japan than to the Miyagi region of their origin, but hatchery stocks more closely resemble the Miyagi population. According to local oyster producers, the one exceptional naturalized population (Tillamook) is a very recent colonization derived from farmed oysters. Such consistency is unexpected under random genetic drift, and thus supports the hypothesis that both natural and artificial selection have strongly altered the genetic composition of these populations. Furthermore, the genetic similarity between the wild Miyagi and Hiroshima populations and all of the domesticated stocks examined makes it reasonable to hypothesize that these populations could have advantages as a source of germplasm for genetic improvement efforts on the US West Coast. Technical Abstract: The Pacific oyster (Crassostrea gigas) is an important commercial species in the US Pacific Northwest with a history of propagation first using wild-caught seed imported directly from the Miyagi region of northern Japan (1920s – 1970s) followed by an extended period of seed collection from a few self-recruiting naturalized populations in the US (early 1970s-present) and more recently through large-scale hatchery production of oyster seed (mid 1970s-present). I studied the genetic level consequences of each of these transitions by examining the patterns of private alleles (bands unique to one sample), the number of polymorphic loci, expected heterozygosity, Nei’s D, and genetic divergence between individuals within and among three native populations in Japan (Hiroshima, Miyagi, Midori River), five naturalized populations in North America (Pipestem Inlet BC, Nootka Inlet BC, Dabob Bay WA, Willapa Bay, WA, and Tillamook Bay, OR), two in New Zealand (Chance Bay and Kaipara Harbor), and seven domesticated and selectively bred cohorts from an ongoing breeding program in Oregon (Molluscan Broodstock Program) using AFLP markers. All but one of the naturalized populations in both the US and New Zealand are genetically more similar to native populations from the Ariake Sea (Midori River) than to the Miyagi region of their origin, but hatchery stocks more closely resemble the Miyagi population. According to local oyster producers, the one exceptional naturalized population (Tillamook) is a very recent colonization derived from farmed oysters. Such consistency is unexpected under genetic drift, and thus supports the hypothesis that both natural and artificial selection have strongly altered AFLP allele frequencies in this species. Furthermore, the genetic similarity between the wild Miyagi and Hiroshima populations and all of the domesticated stocks examined makes it reasonable to hypothesize that these populations could have advantages as a source of germplasm for genetic improvement efforts on the US West Coast. |
