Parental relatedness and survival of Pacific oysters from a naturalized population

Authors: Camara, Mark; EVANS, SANFORD - OREGON STATE UNIVERSITY; LANGDON, CHRIS - OREGON STATE UNIVERSITY

Submitted to: Journal of Shellfish Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/6/2007
Publication Date: 4/30/2008
Citation: Camara, M.D., Evans, S., Langdon, C. 2008. Parental relatedness and survival of Pacific oysters from a naturalized population. Journal of Shellfish Research.27(2):323-336.

Interpretive Summary: Inbreeding is considered an important factor influencing many aspects of organismal- and population-level biology and thus has profound implications ranging from evolutionary biology to medicine. Most cultured aquatic species are only partially domesticated and highly fecund, making inbreeding particularly important in aquaculture because high fecundity species are expected to have higher genetic load and more severe inbreeding depression than species with lower fecundity. Marine bivalves such as oysters are extreme in this regard. Previous studies have demonstrated that self-fertilization, brother/sister matings, and cousin/cousin matings in Pacific oysters (Crassostrea gigas) produce progeny with lower growth and survival than non-consanguineous pairings of parents. It is unclear, however, whether these effects can be extrapolated to the lower levels of consanguinity expected in natural populations or founder populations derived from them to initiate cultured strains and/or selective breeding efforts. To address this without the need for extensive pedigree information, we studied inbreeding in a naturalized population of Pacific oysters using molecular marker-based estimates of parental relatedness calculated from multi-locus microsatellite genotypes. We produced 34 full-sib families using parents collected from a naturalized population in Dabob Bay (Washington, USA) and mated randomly and planted them in both intertidal and subtidal conditions in Dabob Bay and Yaquina Bay (Oregon, USA). Using 16 microsatellite loci, we estimated the degree of inbreeding of each pair’s progeny in three ways: 1) identity or the expected homozygosity of the progeny based on their parents’ genotypes, 2) a moment based estimator of the pair wise coefficient of relatedness of each parental pair, and 3) a modified estimator of the pair wise coefficient of relatedness designed to accommodate null alleles, which were common in the Dabob Bay population. Using analysis of covariance, we found significant negative relationships between all three estimators of inbreeding and the survival of their progeny. Further, these relationships were stronger in Yaquina Bay than in Dabob Bay indicating that inbreeding depression may be more severe in a novel environment. Finally, we briefly outline potential strategies for using molecular marker based related estimates of relatedness to improve the genetic composition of new founder populations, incorporate relatedness information in selective breeding efforts, and minimize these effects of inbreeding in established cultured oyster populations.

Technical Abstract: Inbreeding is considered an important factor influencing many aspects of organismal- and population-level biology and thus has profound implications ranging from evolutionary biology to medicine. Most cultured aquatic species are only partially domesticated and highly fecund, making inbreeding particularly important in aquaculture because high fecundity species are expected to have higher genetic load and more severe inbreeding depression than species with lower fecundity. Marine bivalves such as oysters are extreme in this regard. Previous studies have demonstrated that self-fertilization, brother/sister matings, and cousin/cousin matings in Pacific oysters (Crassostrea gigas) produce progeny with lower growth and survival than non-consanguineous pairings of parents. It is unclear, however, whether these effects can be extrapolated to the lower levels of consanguinity expected in natural populations or founder populations derived from them to initiate cultured strains and/or selective breeding efforts. To address this without the need for extensive pedigree information, we studied inbreeding in a naturalized population of Pacific oysters using molecular marker-based estimates of parental relatedness calculated from multi-locus microsatellite genotypes. We produced 34 full-sib families using parents collected from a naturalized population in Dabob Bay (Washington, USA) and mated randomly and planted them in both intertidal and subtidal conditions in Dabob Bay and Yaquina Bay (Oregon, USA). Using 16 microsatellite loci, we estimated the degree of inbreeding of each pair’s progeny in three ways: 1) identity or the expected homozygosity of the progeny based on their parents’ genotypes, 2) a moment based estimator of the pair wise coefficient of relatedness of each parental pair, and 3) a modified estimator of the pair wise coefficient of relatedness designed to accommodate null alleles, which were common in the Dabob Bay population. Using analysis of covariance, we found significant negative relationships between all three estimators of inbreeding and the survival of their progeny. Further, these relationships were stronger in Yaquina Bay than in Dabob Bay indicating that inbreeding depression may be more severe in a novel environment. Finally, we briefly outline potential strategies for using molecular marker based related estimates of relatedness to improve the genetic composition of new founder populations, incorporate relatedness information in selective breeding efforts, and minimize these effects of inbreeding in established cultured oyster populations.