Comparing and contrasting development and reproductive strategies in the pupal hyperparasitoids Lysibia nana and Gelis agilis (Hymenoptera: Ichneumonidae)

Abstract

In most animals, the optimal phenotype is determined by trade-offs in lifehistory traits. Here, I compare development and reproductive strategies in two species of solitary secondary hyperparasitoids, Lysibia nana and Gelis agilis, attacking pre-pupae of their primary parasitoid host, Cotesia glomerata. Parasitoid larvae of both species exploit a given amount of host resources with similar efficiency. However, adults exhibit quite different reproductive strategies. Both species are synovigenic, and female wasps emerge with no mature eggs. However, G. agilis must first host-feed to produce eggs, while L. nana does not host-feed but mobilizes internal resources carried over from larval feeding to initiate oogenesis. Further, G. agilis is wingless, produces large eggs, has a long life-span, and generates only small numbers of progeny per day, whereas these traits are reversed in L. nana. Given unlimited hosts, the fecundity curve in L. nana was ''front-loaded,'' whereas in G. agilis it was depressed and extended over much of adult life. In L. nana (but not G. agilis), wasps provided with honey but no hosts lived significantly longer than wasps provided with both honey and hosts. Differences in the fecundity curves of the two hyperparasitoids are probably based on differing costs of reproduction between them, with the wingless G. agilis much more constrained in finding hosts than the winged L. nana. Importantly, L. nana is known to be a specialist hyperparasitoid of gregarious Cotesia species that pupate in exposed locations on the food plant, whereas Gelis sp. attack and develop in divergent hosts such as parasitoid cocoons, moth pupae and spider egg sacs. Consequently, there is a strong match between brood size in C. glomerata and egg production in L. nana, but a mismatch between these parameters in G. agilis.

The effect of different dietary sugars and honey on longevity and fecundity in two hyperparasitoid wasps

“…Several studies have shown that resources obtained from host-feeding may be allocated for both reproduction and/or maintenance (Heimpel and Rosenheim, 1995;Heimpel and Collier, 1996;Giron et al, 2002;Rivero and West, 2005;Kapranas and Luck, 2008;Zhang et al, 2011). Host blood is often important in the production of large, yolky 'anhydropic' eggs (Jervis and Kidd, 1986;Bernstein and Jervis, 2006;Harvey, 2008) that are characteristically produced by many 'idiobiont' ectoparasitoids, i.e. parasitoids that attack non-feeding or non-growing host stages or arrest host development prior to oviposition (Godfray, 1994;Harvey, 2005;Jervis and Ferns, 2011).…”

“…Host blood has also been found to contain certain sugars, such as trehalose and sucrose that are important in reducing the metabolism of lipids (Giron et al, 2002). However, this is certainly not the rule, as the longevity of some parasitoids is not extended at all by host-feeding (Rivero and West, 2005;Harvey, 2008). Host-feeding parasitoids are generally highly synovigenic, meaning that the adult female wasps emerge with few or no ripe eggs and therefore mature most of their eggs after eclosion (Ellers et al, 2000;Jervis et al, 2001Jervis et al, , 2008.…”

“…honeydew and nectar, on longevity and fecundity in two closely related species of solitary hyperparasitoids, Lysibia nana Gravenhorst and Gelis agilis Fabricius (Hymenoptera: Ichneumonidae, Cryptinae) that attack the fully cocooned pre-pupae and pupae of C. glomerata in the field. Both species are ectoparasitoids, are wholly synovigenic and produce anhydropic eggs (Harvey, 2008). However, they also exhibit several key differences in reproductive and morphological traits.…”

“…However, they also exhibit several key differences in reproductive and morphological traits. Lysibia nana reproduces sexually and adults are fully winged; by contrast, G. agilis reproduces asexually and adult females are wingless (Harvey, 2008). Another important difference between the two species is that G. agilis females mutilate some host cocoons with their ovipositors and feed on the blood that leaks from the wound as a pre-requisite for egg maturation; L. nana females, on the other hand, do not host-feed (Harvey, 2008).…”

“…Another important difference between the two species is that G. agilis females mutilate some host cocoons with their ovipositors and feed on the blood that leaks from the wound as a pre-requisite for egg maturation; L. nana females, on the other hand, do not host-feed (Harvey, 2008). Furthermore, the reproductive biology and host exploitation behavior of L. nana is closely correlated with brood size in C. glomerata whereas in G. agilis it is not (Harvey, 2008;Harvey et al, 2011). This suggests that L. nana is much more specialized in attacking C. glomerata than G. agilis.…”