Environmental stress increases selection against and dominance of deleterious mutations in inbred families of the Pacific oyster Crassostrea gigas

The deleterious effects of inbreeding are well documented and of major concern in conservation biology. Stressful environments have generally been shown to increase inbreeding depression; however, little is known about the underlying genetic mechanisms of the inbreeding-by-stress interaction and to what extent the fitness of individual deleterious mutations is altered under stress. Using microsatellite marker segregation data and quantitative trait locus (QTL) mapping methods, I performed a genome scan for deleterious mutations affecting viability (viability or vQTL) in two, inbred families of the Pacific oyster Crassostrea gigas, reared in a stressful, nutrient-poor diet and a favorable, nutrient-rich diet, which had significant effects on growth and survival. Twice as many vQTL were detected in the stressful diet compared with the favorable diet, resulting primarily from substantially greater mortality of homozygous genotypes. At vQTL, estimates of selection (s) and dominance (h) were...