The potential additive and non-additive benefits of mate choice in the threespine stickleback (Gasterosteus aculeatus)

Hypothesis: The genetic benefits of female mating preferences can be additive (good alleles'), non-additive ('compatible alleles') or both, and the importance of each may be population dependent. Organism: Threespine stickleback (Gasterosteus aculeatus) from two independent natural populations. Location: Two adjacent sites in Scotland, one a pond with high stickleback density and high parasite prevalence, the other a river with low stickleback density and fish predators. Methods: In vitro fertilizations in a North Carolina Type II breeding design to estimate the contribution of additive and non-additive genetic variation to early offspring survival. Results: In both populations we detected significant additive maternal effects. These effects were largely explained by variance in egg size, though not entirely so. In the pond population there were significant male additive genetic effects on offspring survival, implicating a role for 'good alleles', but not non-additive effects. In the river population there were significant additive and non-additive effects, implicating a role both for 'good alleles' and genetic compatibility. Different populations of the same species may vary in the mechanism by which sexual selection operates.