Performance of secondary parasitoids on chemically defended and undefended hosts

Abstract

Defensive chemicals produced by plants can travel up the food chain by being sequestered by herbivores, and then in turn being sequestered by their parasitoids. Insect species with wide host ranges are predicted to perform poorly in the face of specific chemical defence. However, a species at a high trophic level is expected to have a wide host range. This creates a conflict for hyperparasitoids, many of which depend on specialized hosts. We studied the performance of two hyperparasitoids, Lysibia nana and Gelis agilis, both of which have wide host ranges, on two host species, one chemically defended and the other not. We predicted that both hyperparasitoids would perform better using the undefended host Cotesia glomerata than the defended host C. melitaearum, which sequesters terpenoid allelochemicals (iridoid glycosides). Furthermore, we expected that the progeny of G. agilis collected from an area where hosts defended by iridoid glycosides are absent (the Netherlands) would perform poorly using C. melitaearum in comparison with G. agilis collected from an area where C. melitaearum is a common host (Åland, Finland). In a series of laboratory experiments we found that, contrary to prediction, both hyperparasitoids performed well on both hosts, reaching a larger size on C. glomerata, but having a higher conversion efficiency and developing more quickly on the chemically defended C. melitaearum. Lysibia nana metabolized the plant derived iridoid glycosides, which are chemicals that it does not normally encounter. Gelis agilis retained some of the iridoid glycosides. But whereas Finnish G. agilis retained both aucubin and catalpol, Dutch G. agilis mainly retained aucubin, illustrating that though generalists, local populations still cope differently with toxic allelochemicals. ZusammenfassungVon Pflanzen synthetisierte chemische Abwehrstoffe können sich in der Nahrungskette anreichern, indem sie zunächst von Herbivoren und dann von deren Parasitoiden akkumuliert werden.

Detoxification of plant defensive glucosinolates by an herbivorous caterpillar is beneficial to its endoparasitic wasp

“…The greater physiological intimacy between parasitoids and their hosts compared to predators and their prey may have resulted in parasitoids of insect herbivores being better adapted to the presence of plant defence metabolites in their hosts than predators. Furthermore, parasitoids developing in hosts that contain plants toxins can themselves coopt these plant defences against their own antagonists such as hyperparasitoids (Bowers, 2003; van Nouhuys, Reudler, Biere, & Harvey, 2012) offering them the opportunity to exploit enemy free space, a concept that is usually restricted to insect herbivores (Murphy, Lill, Bowers, & Singer, 2014). Thus, the presence of toxins in their host may not only help protect parasitoids indirectly (avoiding predation of their host), but also directly against their own enemies in the fourth‐trophic level (Murphy et al., 2014).…”

Sequestration and activation of plant toxins protect the western corn rootworm from enemies at multiple trophic levels

“…After being taken up by herbivores, plant defense metabolites may not only influence herbivore predators and parasitoids ( Ode, 2006 ), but also higher trophic levels ( van Nouhuys et al, 2012 ; Harvey et al, 2007 ). Effects extending to four trophic levels may be particularly likely in systems where the third and the fourth trophic level are intimately linked.…”

Host preference and offspring performance are linked in three congeneric hyperparasitoid species

“…However, cocoons of primary parasitoids in the genus Cotesia appear to be particularly susceptible to hyperparasitism by species of Gelis. Gelis agilis reproduces asexually and has been recorded as a hyperparasitoid of Cotesia glomerata (L.) and C. melitaerum W as well as non-parasitoid hosts (Schwarz & Shaw, 1999;van Nouhuys & Hanski, 2000;Harvey, 2008;van Nouhuys et al, 2012) whereas the other two species reproduce sexually but have been little studied and their actual host ranges are poorly known. Here we compare the preference and performance of two wingless Gelis species, G. agilis (Fabricius) and G. acarorum (L.) and the winged G. areator (Panzer) (Fig.…”

“…The wingless Gelis species are restricted to grassy habitats, whereas G. areator prefers to forage higher up in the canopy of forbs . Gelis agilis reproduces asexually and has been recorded as a hyperparasitoid of Cotesia glomerata (L.) and C. melitaerum W as well as non-parasitoid hosts (Schwarz & Shaw, 1999;van Nouhuys & Hanski, 2000;Harvey, 2008;van Nouhuys et al, 2012) whereas the other two species reproduce sexually but have been little studied and their actual host ranges are poorly known. The three Gelis species must feed on host blood in order to produce eggs.…”