Maternal and genetic influences on egg size and larval perfomance in a seed beetle (Callosobruchus maculatus): multigenerational transmission of a maternal effect?

The mechanisms by which maternal effects are transmitted across generations are variable among characters and taxa. Because egg size is simultaneously a maternal and offspring character, and variation in egg size often has implications for offspring life histories, egg size may facilitate multigenerational transmission of maternal effects. The relative contributions of genetic and maternal effects to variation in egg size and offspring performance (body size and development time), with an emphasis on maternal contributions to offspring egg sizes (and thus granddaughter phenotype), are estimated in the seed beetle, Callosobruchus maculatus, using a half-sib quantitative genetic design. Both body size and egg size (egg length and width) were highly heritable characters (estimated h2 > 0.55 for each character), and the proportion of the variance explained by maternal effects was near zero for each. Maternal effects do, however, appear to affect early larval life history through a female body size effect on hatchling resources (estimated as egg size). This initial disadvantage to larvae results in extended larval development time, but not in an effect on final adult size. These results indicate that variation in egg size and body size are not maternally transmitted across generations, but instead that most of the variation in body size and egg size is additive genetic variation.