Sources of phenotypic variance in egg and larval traits in a marine invertebrate

Contrary to many separate sex systems, the evolutionary ecology of polyandry in simultaneous hermaphrodites, and in particular in those with internal fertilization, has received little attention. Recent studies on the promiscuous gastropod Chelidonura sandrana showed that offspring size, an important determinant of offspring performance in many marine invertebrates, varies with the number of different mating partners. However, the source of this differential allocation by mothers remained unclear. Using a quantitative genetic model, we here tested for parental effects on offspring size and the importance of ‘good gene’ effects on early life history traits. Our analysis revealed no significant sire but strong dam effects for all investigated traits. Moreover, embryo viability tended to increase with egg capsule volume, thus linking offspring size with offspring performance. Our findings suggest that in C. sandrana (1) differential allocation is a maternal effect in response to the number of different partners, and that (2) additive genetic variance is of negligible importance in early life history traits.