Size-mediated adaptive foraging: a host-selection strategy for insect parasitoids (original) (raw)
Related papers
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.
Functional Ecology, 2017
- Life-history traits within ecological communities can be influenced by regional environmental conditions (external filters) and community-wide density-dependent processes (internal filters). While traits in a regional context may converge to a narrow range of values because of environmental filtering, species belonging to a guild may present contrasting traits as a means of niche differentiation, allowing coexistence whilst exploiting the same resources. 2) To disentangle the role of external and internal filters on phenotypic diversity within ecological communities, we examined the patterns of life-history trait variation within a guild of insect parasitoids during two successive years across three contrasted regions in relation to several ecological factors. 3) By combining a mean-field approach and an analysis of phenotypic variance across organizational levels (from individual to guild), we showed that the patterns of life-history Accepted Article. trait variation across regions are consistent with local adaptation or adaptive phenotypic plasticity while the patterns of phenotypic variation within regions suggested how coexistence modulates life-history traits expression through niche differentiation. 4) Within a given region, phenotypic pattern of parasitoid life-history traits may also arise from bottom-up effects of trophic webs: insect host species could also control parasitoid life-history traits in nature. Our results also showed that parasitoid life-history traits presented contrasting variation patterns according to the sampling year, suggesting temporal variations in evolutionary and ecological dynamics of parasitoid species. 5) The application of such trait-based studies to insect parasitoids has the potential to provide further insight on how agricultural environments contribute to differential diversification among natural enemies guilds, highlighting the main role of agricultural landscape management for organisms' responses.
Fitness consequences of body-size-dependent host species selection in a generalist ectoparasitoid
Behavioral Ecology and Sociobiology, 2004
In insect parasitoids, offspring fitness is strongly influenced by the adult female's choice of host, particularly in ectoparasitoids that attack non-growing host stages. We quantified the fitness consequences of size-dependent host species selection in Dirhinus giffardii, a solitary ectoparasitoid of tephritid fruit fly pupae. We first showed a positive correlation between the size of emerged D. giffardii wasps and the size of their host fruit fly species (in order of decreasing size): Bactrocera latifrons, B. cucurbitae, B. dorsalis or Ceratitis capitata. We then manipulated individual wasps to show that the parasitoid preferred to attack the largest (B. latifrons) to the smallest (C. capitata) host species when provided with a choice, and laid a greater proportion of female eggs in B. latifrons than in C. capitata. There were no differences in developmental time or offspring survival between individuals reared from these two host species. Finally, we compared the foraging efficiency of large versus small wasps (reared from B. latifrons vs C. capitata) under two different laboratory conditions: high versus low host habitat quality, given that realized fecundity in parasitoids may be influenced by either egg-limited or time-limited factors. Under both conditions, large wasps parasitized more hosts than did small ones as a consequence of high searching efficiency in the host-poor habitat, and high capacity for adjusting egg maturation in response to host availability in the host-rich habitat. Considering the flexibility of body growth, the apparent lack of cost of achieving large body size in either development or survival, and the strong dependence of realized reproductive success on a female's size, we argue that body size may be a key to understanding evolution of host species selection in ectoparasitoids. We also discuss constraints upon the evolution of size-dependent host species selection in parasitoids.
2021
The quality of hosts for a parasitoid wasp may be influenced by attributes such as host size or species, with high quality for successful development usually coincident with high quality for larger offspring. This is not always the case: for the Scelionid wasp Trissolcus basalis, oviposition in eggs of the Brown Marmorated Stink Bug, Halyomorpha halys, rather than of the normal host, the Southern Green Stink Bug, Nezara viridula, leads to lower offspring survival, but survivors can be unusually large. Adult female T. basalis engage in contests for host access. As larger contestants are typically favoured in contests between parasitoids, the larger size of surviving offspring may compensate for the mortality of others. We construct a general game-theoretic model to explore whether size advantage can sustain a maternal preference to utilize a more deadly host species. We find that size advantage alone is unlikely to sustain a shift in host preference, yet such an outcome is possible w...
Body sizes of hosts and parasitoids in individual feeding relationships
Proceedings of the National Academy of Sciences, 2005
In a natural community of 49 species (12 species of aphids and 37 species of their parasitoids), body lengths of 2,151 parasitoid individuals were, to an excellent approximation, related to the body lengths of their individual aphid hosts by a power law with an exponent close to 3͞4. Two alternative models predict this exponent. One is based on surface area to volume relationships. The other is based on recent developments in metabolic ecology. Both models require a changing ratio (in both host and parasitoid) of length to diameter with increasing body length. These changing ratios are manifested differently in the two models and result in testably different predictions for the scaling of body form with increasing size. The estimated exponent of 3͞4 for the relationship between individual host body size and individual parasitoid body size degrades to an exponent of nearly 1͞2, and the scatter in the relationship between aphid and parasitoid body length is substantially increased, if the average length of a parasitoid species is examined as a function of the average length of its aphid host species instead of using measurements of individuals.
Ecological Entomology, 2008
Abstract 1. In solitary parasitoids, several species can exploit the same host patch and competition could potentially be a strong selective agent as only one individual can emerge from a host. In cereal crops, Aphidius rhopalosiphi and A. ervi share the grain aphid Sitobion avenae as host.2. The present work studied foraging strategies of both species on patches already exploited by the other species. The study analysed larval competition in multi-parasitised hosts and compared the foraging behaviour of females with and without previous experience.3. It was found that A. ervi wins larval competition three times more often than A. rhopalosiphi. Both species spent less time on patches exploited by a heterospecific than on unexploited ones. When they foraged on heterospecifically exploited patches, experienced females induced less mortality in aphids than inexperienced ones.4. Although A. rhopalosiphi is a specialist on cereal aphids and is the most abundant species due to its early appearance in the season, S. avenae is still a profitable host for A. ervi, because: (i) A. rhopalosiphi leaves patches partially exploited, (ii) A. ervi wins larval competition in three out of four multi-parasitised hosts, and (iii) A. ervi is only slightly deterred by the cornicular secretions of the host and can thus easily parasitise hosts.
Evolutionary and population dynamics of host–parasitoid interactions
Population Ecology, 1999
to their hosts for all aspects of their development and survival. Parasitoids account for almost a fifth of all Metazoa known and exhibit a complex and wide variety of physiologies, behaviors, and life strategies. This variation in parasitoid life history characteristics can occur at the individual level, the population scale, and the regional level, and analyzing the expression of this genetic variation on which selection acts is grist to the mill for life history evolution (Roff 1992). Not only do parasitoids provide model organisms for understanding the life history evolution and population dynamics of predator-prey interactions (Hassell 1978; Godfray 1994; Quicke 1997), but also these organisms are of considerable economic importance in the control of pest populations (Waage and Greathead 1986; Gauld and Bolton 1988). In this article we explore the population and evolutionary dynamics of host-parasitoid interactions. We begin by examining the constraints on genetic covariance and tradeoffs in parasitoid wasps. We then provide an overview of some previous theoretical and empirical studies before introducing a general host-parasitoid model and demonstrating how evolution can alter the dynamics of host-parasitoid interactions. We then consider a simple evolutionary interaction between hosts and parasitoids, examining the conditions for the evolution of parasitoid virulence. In the final section we comment on directions for future work. Trade-offs and genetic covariance At the level of the individual wasp, many phenotypic traits are highly variable. For example, egg size, shape, and number in many parasitoids such as the Ichneumonidae or Chalcidae are highly variable (Iwata 1958, 1962, 1966). How these morphological and reproductive strategies of wasps (how many eggs to lay and what sex ratio to produce) impinge on life history strategies have been the focus of much research (Charnov et al.