Effects of superparasitism, larval competition, and host feeding on offspring fitness in the parasitoid Pimpla nipponica (Hymenoptera: Ichneumonidae) (original) (raw)
Related papers
Impact of mating status on egg-laying and superparasitism behaviour in a parasitoid wasp
Entomologia Experimentalis et Applicata, 2007
Most parasitoid female wasps can distinguish between unparasitized and parasitized hosts and use this information to optimize their progeny and sex allocation. In this study, we explored the impact of mating on oviposition behaviour (parasitism and self-and conspecific superparasitism) on both unparasitized and already parasitized hosts in the solitary parasitoid wasp Eupelmus vuilleti (Crw.) (Hymenoptera: Eupelmidae). Virgin and mated females had the same oviposition behaviour and laid eggs preferentially on unparasitized hosts. The sex ratio (as the proportion of females) of eggs laid by mated females in parasitism and conspecific superparasitism was 0.67 ± 0.04 and 0.57 ± 0.09, respectively. Likewise, females laid more eggs in conspecific superparasitism than self-superparasitism under our experimental conditions. These experiments demonstrate that E. vuilleti females can (i) discriminate between unparasitized and parasitized hosts and adapt the number of eggs they lay accordingly, and (ii) probably discriminate self from conspecific superparasitized hosts. Finally, mating does not appear to influence the host discrimination capacity, the ovarian function, or the oviposition behaviour.
Journal of Insect Behavior, 2000
Host rejection, superparasitism, and ovicide are three possible host selection strategies that parasitoid females can adopt when they encounter parasitized hosts. These differ in costs (in terms of time and energy required) and benefits (in terms of number and quality of offspring produced). Their relative payoff should vary with patch quality, (i.e., proportion of parasitized hosts present), and female choice between them should be adapted accordingly. We conducted behavioral observations to test the effect of the ratio of parasitized/unparasitized hosts present in a patch on the host selection strategies of Pachycrepoideus vindemmiae Rondani (Hymenoptera: Pteromalidae). This species being a generalist known to attack hosts of a great range of size, we also tested the impact of host size on female decisions with two host species differing greatly in size (Drosophila melanogaster and Delia radicum). We evaluated the adaptive value of each strategy in relation to host parasitization status and host size by measuring their duration and the potential number of offspring produced.
Annals of the Entomological Society of America, 1999
In general, several parasitoids are associated with 1 host species, leading to competition among the parasitoids. To test whether female parasitoids decided to multiparasitize based on the probability of the offspring survival, multiparasitism and larval competition in the 2 coexisting solitary parasitoids Pimpla nipponica Uchida and Itoplectis naranyae Ashmead were studied. Females of both species readily multiparasitized when time intervals between the attacks were short. However, they avoided multiparasitism with increasing time intervals while they increasingly fed on parasitized hosts. The survival of offspring of the 2nd parasitoid decreased with increasing time intervals between the attacks and was positively correlated with the degree of multiparasitism. The degree of host-feeding in both species was also negatively correlated with offspring survival. These results suggest that females multiparasitized or host-fed on the basis of their offspring survival. Larvae of the 1st parasitoid were killed by the 2nd parasitoid via host-feeding, suggesting that preferential host-feeding on parasitized hosts could be a form of interspeciÞc competition. Multiparasitism and host-feeding strategies in parasitoids were discussed. Further, it was suggested that parasitoid tendencies to feed on parasitized hosts could affect host-parasitoid dynamics and competition among parasitoids.
Does Host Value Influence Female Aggressiveness, Contest Outcome and Fitness Gain in Parasitoids?
Ethology, 2007
Intraspecific competition for resources is common in animals and may lead to physical contests. Contest outcomes and aggressiveness can be influenced by the resource holding potential of contestants but also by their perception of the resource value (RV). Competitors may assess resource quality directly (real RV) but may also estimate it according to their physiological status and their experience of the habitat quality (subjective RV). In this article, we studied contests between females of the solitary parasitoid Pachycrepoideus vindemmiae Rondani (Hymenoptera: Pteromalidae) when exploiting simultaneously a host, a Delia radicum L. (Diptera: Anthomyiidae) pupa. We tested the effect of factors modifying host value on the occurrence of agonistic behaviours, contest outcomes and host exploitation. The factors tested were: the quality of the previous habitat experienced by females, female egg load, host parasitism status and the stage reached by the owner female in her behavioural oviposition sequence. Females successfully protected their host against intruders during its exploitation, but not after oviposition, and their aggressiveness did not seem to be influenced by their perception of the RV. The fact that the host is subsequently parasitized by the opponent females appears to mainly depend on the host selectiveness of females.
Population Ecology, 1986
During the summer of 1969-70, the New Zealand Department of Scientific and Industrial Research released four species ofparasiticwasps (Hymenoptera: Chalcidoidea) at selected sites throughout New Zealand to assist in the biological control of the house fly, Musca domestica L, and other flies associated with man. The species were Muscidifurax zaraptor KOOAN and LEONER, M. uniraptor K & L, Pachycrepoideus vindemiae RONDANI, and Spalangia endius WALKER. The native hosts and the geographic distribution of these species are described by BOUCEK (1963), LEGNER and BRYDON (1966), LEONER and OLTON (1968), and CUMBER (1969). Experiments, including a study of egg-laying behaviour, were undertaken by the second author to determine population growth potential of the parasites under controlled physical conditions. As an aid to interpreting experimental results we exploit a group of probability models whose use for describing the avoidance ofsuperparasitism is proposed in DALEY and MAINDONALD (1982). These models have the merit that their form can be varied to investigate alternative biological mechanisms. Problems in handling the estimation for one of these models lead us to use, in one instance, the closely equivalent model which is an extension of GRIFFITHS (1977a, 1977b). "Superparasitism", as used in this paper, refers to the laying of more than one egg on a house fly pupa (WYLIE, 1965). METHODS AND MATERIALS In the first group of experiments ('uncrowded conditions') a solitary female was placed in a vial with 5, 15, or 30 host pupae. Twenty replicates were in each instance taken. In a second series of experiments 10 females were placed, under deliberately more crowded conditions, with 50 hosts. Ten replicates were taken in each instance. Except for the uniparental species M. uniraptor an equal number of male parasites was always included. Conditions were maintained at 26-4-1.5~ 60% RH and 12-h photoperiod.
The function of host discrimination and superparasitization in parasitoids
Oecologia, 1985
Host discrimination, i.e. the ability to distinguish unparasitized hosts from parasitized ones, and to reject the latter for egg laying is present in many parasitic wasp species. This property is classically considered as an example of contest competition, and is supposed to have a number of functions. However, different species do not react to each other's marks and lay eggs in hosts parasitized by the other species. Apparently the marks used for recognition are specific. Multiparasitization is the best strategy when hosts are scarce and the egg supplies of the parasitoids are not limited. Interspecific host discrimination is not an ESS. Superparasitization within one species would have selective advantage if the number of unparasitized hosts is small and the wasp has a reasonable chance to lay her egg in a host that is not parasitized by herself, and if the chance for her offspring to survive the competitive battle with the first parasitoid larva is not too small. This is shown to be the case. However, marks are not individual and wasps cannot distinguish hosts parasitized by themselves from those parasitized by others. The hypothesis is tested that the egg laying strategy (i.e. the decision to superparasitize) of wasps is dependent on the number of conspecifics that is searching simultaneously for hosts, since this determines the chance that a parasitized host encountered by a wasp is parasitized by herself. It is shown that host discrimination cannot be regarded as a case of contest competition. Other aspects of superparasitization, related to interference and population regulation, sex allocation and encapsulation are briefly discussed.
Host choice decisions in the polyembryonic wasp Copidosoma koehleri (Hymenoptera: Encyrtidae)
Physiological …, 2010
Female parasitoids often reject hosts of poor quality, where the survival and fitness of their offspring are expected to be low. In polyembryonic parasitoid wasps, a clone of genetically identical embryos develops from one egg in a host. In the wasp Copidosoma koehleri, each female clone produces one soldier larva that attacks competing clones inside the host. Aggression by soldiers is directed usually towards unrelated clones. Accordingly, it may be predicted that females will prefer nonparasitized over parasitized hosts, especially if the latter have been parasitized previously by a mated unrelated female, as a result of the reduced chances of survival for their offspring inside these hosts. In accordance with these predictions, females prefer nonparasitized hosts over self-parasitized hosts when they are presented simultaneously. By contrast to the predictions, females prefer hosts parasitized by an unrelated conspecific over nonparasitized hosts when presented simultaneously. Females do not distinguish hosts parasitized by conspecifics from self-parasitized hosts when presented simultaneously. They reject self-parasitized hosts significantly more often than hosts parasitized by conspecifics when each host type is presented alone. Females faced with two previously parasitized hosts are not affected in their choice by the mating status (i.e. virgin or mated) of the previous parasitizing females. The combined results suggest that females are limited in their ability to assess the risk that their offspring will be attacked by a soldier, or that this risk is balanced by the relative advantages of ovipositing in a host parasitized by conspecifics. A possible advantage may be increased out-breeding opportunities for the emerging offspring.