Superparasitism indicates an increase of individual offspring fertility by reducing parents’ fertility in gregarious parasitoids

Abstract

The gregarious parasitoid strategy allows multiple larvae to complete development in a single host due to their tolerance and/or lower mobility, and thus flexibly adjust their reproductive potential. Reproductive potential is traditionally measured as the number of each mother’s offspring. In our previous study we showed the benefits of an intergenerational approach to assessess the fitness through measuring fertilities in F1 and F2 generation – bringing possible predictions about the future population density of parasitoids and their use in biological control. Here, again using the gregarious parasitoid Anaphes flavipes as model species, we experimentally demonstrate the effects of superparasitism due to scarcity of host on fertility. Whereas the conventional approach would assume a simple reduction of female fertility, our intergenerational approach shows that the reduction of female fertility translates as an actual increase in the individual offspring fertility. We showed the same effect using an experiment where females had different visual interactions and different timings between parasitation. The fertility of females did not differ, but the distribution of clutch sizes, and consequently the body size and fertility of the offspring, was statistically different. The intergenerational approach in these groups therefore reveals a fertility difference in the F2 generation that is not visible from the F1 generation.