Intraspecific variability in egg maturation patterns and associated life-history trade-offs in a polyembryonic parasitoid wasp

Abstract

1. Life-history theory predicts a trade-off between the resources allocated to reproduction and those allocated to survival. Early maturation of eggs (pro-ovigeny) is correlated with small body size and low adult longevity in interspecific comparisons among parasitoids, demonstrating this trade-off. The handful of studies that have tested for similar correlations within species produced conflicting results. 2. Egg maturation patterns and related life-history traits were studied in the polyembryonic parasitoid wasp, Copidosoma koehleri (Hymenoptera: Encyrtidae). Although the genus Copidosoma was previously reported to be fully pro-ovigenic, mean egg loads of host-deprived females almost doubled within their first 6 days of adulthood. 3. The initial egg-loads of newly emerged females were determined and age-specific realised fecundity curves were constructed for their clone-mate twins. The females' initial egg loads increased with body size, but neither body size nor initial egg load was correlated with longevity and fecundity. 4. The variation in initial egg loads was lowest among clone-mates, intermediate among non-clone sisters and highest among non-sister females. The within-clone variability indicates environmental influences on egg maturation, while the between-clone variation may be genetically based. 5. Ovaries of host-deprived females contained fewer eggs at death (at ∼29 days) than on day 6. Their egg loads at death were negatively correlated with life span, consistent with reduced egg production and/or egg resorption. Host deprivation prolonged the wasps' life span, suggesting a survival cost to egg maturation and oviposition. 6. It is concluded that adult fecundity and longevity were not traded off with pre-adult egg maturation.