General and specific combining abilities of larval and juvenile growth and viability estimated from natural oyster populations

Abstract

Diallel crosses of oysters from three geographically isolated natural populations were produced to evaluate the relative importance of genetic, maternal, and environmental effects on larval and juvenile growth and viability. Significant additive genetic effects were observed only in larval viability at Day 12 and larval shell length at Day 2. The presence of significant male and female mean square for larval viability (suggesting non-additive genetic variance) is consistent with fitness related characters. Important maternal effects were observed for the larval and juvenile shell length and viability characters. These female mean squares are probably affected by both real and spurious maternal effects and potential contributing influences are discussed. The performance of the crosses can be largely explained by two factors: parental performance and the heterotic gene effects. This is based on an apparent positive correlation of mean values between the parental populations and their crosses. The crosses' mean viability at the end of the larval phase was 14.0% lower than the pure matings and support a previous observation of lower heterozygote viability in the larval phase (Mallet and Haley, 1983b).