Maternal effects on offspring depend on female mating pattern and offspring environment in yellow dung flies.

Direct costs and benefits to females of multiple mating have been shown to have large effects on female fecundity and longevity in several species. However, with the exception of studies examining genetic benefits of polyandry, little attention has been paid to the possible effects on offspring of multiple mating by females. We propose that nongenetic effects of maternal matings on offspring fitness are best viewed in the same context as other maternal phenotype effects on offspring that are well known even in species lacking parental care. Hence, matings can exert effects on offspring in the same way as other maternal environment variables, and are likely to interact with such effects. We have conducted a study using yellow dung flies (Scathophaga stercoraria), in which we independently manipulated female mating rate, number of mates and maternal thermal environment and measured subsequent fecundity, hatching success, and offspring life-history traits. To distinguish between direct effects of matings and potential genetic benefits of polyandry we split broods and reared offspring at three different temperature regimes. This allowed us to demonstrate that although we could not detect any simple benefits or costs to matings, there are effects of maternal environment on offspring and these effects interact with female mating regime affecting offspring fitness. Such interactions between female phenotype and the costs and benefits of matings have potentially broad implications for understanding female behavior.