Life-history strategies in parasitoid wasps: a comparative analysis of 'ovigeny'

1. Ecologists concerned with life-history strategies of parasitoid wasps ha ve recently focused on interspecific variation in the fraction of the maxim um potential lifetime egg complement that is mature when the female emerges into the environment. Species that have all of this complement mature upon emergence are termed 'pro-ovigenic', while those that do not are termed 's ynovigenic'. We document and quantify the diversity of egg maturation patte rns among 638 species of parasitoid wasps from 28 families. 2. We test a series of hypotheses concerning variation in 'ovigeny' and lik ely life-history correlates by devising a quantitative index - the proporti on of the maximum potential lifetime complement that is mature upon female emergence. 3. Synovigeny, which we define as emerging with at least some immature eggs , was found to be by far the predominant egg maturation pattern (98.12% of species). Even allowing for some taxonomic bias in our sample of species, p ro-ovigeny is rare among parasitoid wasps. 4. There is strong evidence for a predicted continuum in ovigeny index amon g parasitoid wasps, from pro-ovigenic (ovigeny index = 1) to extremely syno vigenic species (ovigeny index = 0). 5. As predicted, synovigenic species are longer-lived than pro-ovigenic one s, and ovigeny index and life span are negatively correlated across parasit oid taxa, suggesting a life span cost of concentrating reproductive effort early in adult life. 6. There is equivocal evidence that host feeding (i.e, consumption of host haemolymph and/or tissues by adult wasps) is confined to synovigenic parasi toid wasps. It is also not certain from our analyses whether host feeding i s associated with a relatively low ovigeny index. 7. As predicted, egg resorption capability is concentrated among producers of yolk-rich eggs. Also, the hypothesis that it is associated with a tenden cy towards a low ovigeny index is supported. Parasitoid species that produc e yolk-rich eggs also exhibit a lower ovigeny index than species that produ ce yolk-deficient eggs. 8. Ovigeny index appears to be linked to parasitoid development mode (koino biosis-idiobiosis). 9. We conclude that 'ovigeny' is a concept applicable to insects generally.