Effects of size, shape, genotype, and mating status on queen overwintering survival in the social wasp Vespula maculifrons.

Many insects survive cold winter temperatures by entering into a transient, dormant state. Social wasp queens in the genus Vespula undergo such a state of physiological dormancy known as diapause to survive winter conditions. We experimentally investigated the effects of size, shape, genotype, and matedness on the overwintering survival of Vespula maculifrons Buysson (Hymenoptera: Vespidae) queens in two study years. Queens first were mated in the laboratory and then subjected to overwintering conditions. The sizes of several morphological traits of each queen were measured, and the genotype of each queen was determined at polymorphic microsatellite loci allowing queens to be assigned to distinct patrilines. We found that overall large body size resulted in high overwintering survival for queens in one study year. In addition, queen thinness was positively and significantly associated with overwintering survival in both years. In contrast, we found no evidence for an effect of patriline on overwintering survival, which is consistent with the idea that natural selection removes genetic variation associated with traits directly linked to fitness. We also found no effect of queen matedness on overwintering survival, as expected under models suggesting that mating should not adversely affect female viability in social hymenopteran insects. Overall, our study demonstrates that some aspects of body size and shape are significantly associated with overwintering survival in V. maculifrons queens. However, variation in survival arising from genotypic differences or mating effects is limited due, in part, to the way selection operates in social insect species.