Effects of maternal diet quality on offspring performance in the rove beetle Tachyporus hypnorum

1. The reproductive output of an individual is known to be influenced by diet quality, but the quality of the parent's diet can also influence the performance of the offspring. Dietary maternal effects may interact with the effects of the offspring's diet to produce a variety of response patterns. 2. Maternal effects were investigated in a polyphagous predator, the rove beetle Tachyporus hypnorum, using three single-species diets: two low-quality diets consisting of the aphids Sitobion avenae and Rhopalosiphum padi, and the high-quality control Drosophila melanogaster diet. Offspring of females fed these diets were raised on the same monotypic diets and allowed to reproduce. Several fitness parameters were measured to indicate possible maternal effects in both F1 and F2 generations. 3. Maternal diet effects in F1 were found in egg size, hatching success, time to hatching, larval development time, larval survival, and sex ratio. Both aphid diets resulted in smaller eggs. A diet of R. padi resulted in reduced hatching success, longer time spent in the egg stage, and a female-biased sex ratio. A maternal diet of R. padi also prolonged larval development on S. avenae diet, while a maternal diet of S. avenae decreased survival on the R. padi diet. These effects were independent of egg size. 4. A maternal diet of R. padi enhanced the survival of F1 larvae raised on the same diet. Developmental selection operating through a high egg mortality may be the explanation for this seemingly positive effect. 5. Sitobion avenae alone caused a significant reduction in the hatching success of F2 eggs, thus revealing grandmaternal effects. 6. The prediction that polyphagous predators are less likely to evolve adaptive maternal effects is supported by the fact that none of the documented maternal effects could be interpreted as adaptive.