Nonadditive indirect effects of group genetic diversity on larval viability in Drosophila melanogaster imply key role of maternal decision-making

Genetic variation can have important consequences for populations: high population genetic diversity is typically associated with ecological success. Some mechanisms that account for these benefits assume that local social groups with high genetic diversity are more successful than low-diversity groups. At the same time, active decision-making by individuals can influence group genetic diversity, a behavioral process not generally incorporated into discussions of population-level diversity effects. Here, we examine how maternal decisions that determine group genetic diversity influence the viability of Drosophila melanogaster larvae. Our groups contained wildtype larvae, whose genetic diversity we manipulated; and genetically-marked “tester” larvae, whose genotype and frequency were identical in all trials. We measured wildtype and tester viability for each group. Surprisingly, the viability of wildtype larvae did not depend on group genetic diversity. However, the viability of the test...