Intrinsic competition between two secondary hyperparasitoids results in temporal trophic switch
Harvey, J.A. ; Pashalidou, F.G. ; Soler, R. ; Bezemer, T.M. - \ 2011
Oikos 120 (2011)2. - ISSN 0030-1299 - p. 226 - 233.
solitary parasitoid wasp - physiological suppression - leptopilina-heterotoma - insect parasitoids - interspecific competition - intraguild predation - host discrimination - aphytis-melinus - lysibia-nana - superparasitism
Interspecific competition amongst parasitoids is important in shaping the evolution of life-history strategies in these insects as well as community structure. Competition for hosts may occur between adult female parasitoids (‘extrinsic’ competition) or their progeny (‘intrinsic’ competition). Here, we examined intrinsic competition between two solitary secondary hyperparasitoids, Lysibia nana and Gelis agilis in cocoons of a primary parasitoid, Cotesia glomerata. Each species was allowed to sting hosts previously parasitized by the other at 24 h time intervals over the course of 144 h (6 days). When hosts were attacked simultaneously, neither species was dominant although the species to attack first won most encounters when it had a 24–48 h head start. However, after this time there was dramatic shift in the outcome with G. agilis dominating in all hosts > 72-h old, regardless of which species had parasitized C. glomerata first. G. agilis larvae, which initially had competed with L. nana for control of C. glomerata resources, began attacking the larvae of L. nana, whereas L. nana rejected hosts with older G. agilis larvae or pupae. Effects of multiparasitism also affected the development time and adult mass of the winning parasitoid. Our results reveal a shift in the trophic status of G. agilis from C. glomerata (in younger hosts) to L. nana (in older hosts), the first time such a phenomenon has been reported in parasitoids
Importance of host feeding for parasitoids that attack honeydew-producing hosts
Burger, J.M.S. ; Komany, A. ; Lenteren, J.C. van; Vet, L.E.M. - \ 2005
Entomologia Experimentalis et Applicata 117 (2005)2. - ISSN 0013-8703 - p. 147 - 154.
lifetime reproductive success - encarsia-formosa - trialeurodes-vaporariorum - aphytis-melinus - insect parasitoids - bemisia-tabaci - egg-production - hymenoptera - wasp - strategies
Insect parasitoids lay their eggs in arthropods. Some parasitoid species not only use their arthropod host for oviposition but also for feeding. Host feeding provides nutrients to the adult female parasitoid. However, in many species, host feeding destroys an opportunity to oviposit. For parasitoids that attack Homoptera, honeydew is a nutrient-rich alternative that can be directly imbibed from the host anus without injuring the host. A recent study showed that feeding on host-derived honeydew can be an advantageous alternative in terms of egg quantity and longevity. Here we explore the conditions under which destructive host feeding can provide an advantage over feeding on honeydew. For 5 days, Encarsia formosa Gahan (Hymenoptera: Aphelinidae) parasitoids were allowed daily up to 3 h to oviposit until host feeding was attempted. Host feedings were either prevented or allowed and parasitoids had ad libitum access to honeydew between foraging bouts. Even in the presence of honeydew, parasitoids allowed to host feed laid more eggs per hour of foraging per host-feeding attempt than parasitoids that were prevented from host feeding. The higher egg-laying rate was not compromised by survival or by change in egg volume over time. In conclusion, host feeding can provide an advantage over feeding on honeydew. This applies most likely under conditions of high host density or low extrinsic mortality of adult parasitoids, when alternative food sources cannot supply enough nutrients to prevent egg limitation. We discuss how to integrate ecological and physiological studies on host-feeding behavior
Host feeding in insect parasitoids: why destructively feed upon a host that excretes an alternative?
Burger, W. ; Reijnen, T.M. ; Lenteren, J.C. van; Vet, L.E.M. - \ 2004
Entomologia Experimentalis et Applicata 112 (2004)3. - ISSN 0013-8703 - p. 207 - 215.
trialeurodes-vaporariorum homoptera - encarsia-formosa hymenoptera - alfalfa weevil coleoptera - aphytis-melinus - honeydew sugars - aphelinidae - aleyrodidae - food - strategies - evolutionary
Host feeding is the consumption of host tissue by the adult female parasitoid. We studied the function of destructive host feeding and its advantage over non-destructive feeding on host-derived honeydew in the whitefly parasitoid Encarsia formosa Gahan (Hymenoptera: Aphelinidae). We allowed parasitoids to oviposit until they attempted to host feed. We either prevented or allowed host feeding. Parasitoids had access to sucrose solution, with or without additional access to honeydew. Parasitoids that were allowed to host feed did not have a higher egg load 20 or 48 h after host feeding than parasitoids prevented from host feeding. Host feeding did not increase the number of eggs matured within these periods, nor did the time spent host feeding positively affect any of these response variables. On the other hand, the presence of honeydew did have a positive effect on egg load 20 and 48 h after host feeding compared with parasitoids deprived of honeydew. Parasitoids with access to honeydew matured more eggs within these periods than honeydew-deprived parasitoids. Host feeding increased life expectancy, but this effect was nullified when honeydew was supplied after the host-feeding attempt. In conclusion, feeding on honeydew could be an advantageous alternative to host feeding in terms of egg quantity and longevity. This applies especially to parasitoids exploiting Homoptera, because these parasitoids can obtain honeydew from the host itself. It is possible that destructive host feeding has evolved to enable females to sustain the production of high-quality anhydropic eggs, which may be important in the parasitoid's natural environment. We argue that future studies should take natural alternative food sources into more consideration.
Reproduction now or later: optimal host-handling strategies in the whitefly parasitoid Encarsia formosa
Burger, J.M.S. ; Hemerik, L. ; Lenteren, J.C. van; Vet, L.E.M. - \ 2004
Oikos 106 (2004)1. - ISSN 0030-1299 - p. 117 - 130.
trialeurodes-vaporariorum homoptera - gerbera-jamesonii leaves - foraging behavior - egg load - aphytis-melinus - hymenoptera-aphelinidae - gahan hym - evolutionary argument - lethal interference - feeding strategies
We developed a dynamic state variable model for studying optimal host-handling strategies in the whitefly parasitoid Encarsia formosa Gahan (Hymenoptera: Aphelinidae). We assumed that (a) the function of host feeding is to gain nutrients that can be matured into eggs, (b) oogenesis is continuous and egg load dependent, (c) parasitoid survival is exponentially distributed and (d) parasitoids encounter hosts randomly, are autogenous and have unlimited access to non-host food sources to obtain energy for maintenance and activity. The most important prediction of the model is that host feeding is maladaptive under field conditions of low host density (0.015 cm(-2)) and short parasitoid life expectancy (maximum reproductive period of 7 d). Nutrients from the immature stage that can be matured into eggs are sufficient to prevent egg limitation. Both host density and parasitoid life expectancy have a positive effect on the optimal host-feeding ratio. Parasitoids that make random decisions gain on average only 35% (0.015 hosts cm(-2)) to 60% (1.5 hosts cm(-2)) of the lifetime reproductive success of parasitoids that make optimal decisions, independent of their life expectancy. Parameters that have a large impact on lifetime reproductive success and therefore drive natural selection are parasitoid life expectancy and the survival probability of deposited eggs (independent of host density), the number of host encounters per day (when host density is low) and the egg maturation rate and number of host types (when host density is high). Explaining the evolution of host-feeding behaviour under field conditions requires field data showing that life expectancy in the field is not as short as we assumed, or may require incorporation of variation in host density. Incorporating variation in walking speed, parasitised host types or egg resorption is not expected to provide an explanation for the evolution of host-feeding behaviour under field conditions.