The theoretical value of encounters with parasitized hosts for parasitoids (original) (raw)
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Information Acquisition, Information Processing, and Patch Time Allocation in Insect Parasitoids
Behavioral Ecology of Insect Parasitoids, 2008
Resources that animals depend on for growth, maintenance, and reproduction are usually heterogeneously distributed. Animals foraging in a heterogeneous environment face complex decisions. This is particularly the case for insect parasitoids foraging for hosts, for whom one of the key questions is how to allocate search time over patches in the habitat. To cope with this problem and to make adaptive decisions, parasitoids must acquire and integrate the information provided by a large variety of cues. We review the wealth of information parasitoids integrate, such as time spent in the patch, ovipositions performed, the chemicals deposited by hosts, contacts with parasitized hosts, etc. Recently, it has also been shown that contacts with conspecifics, the internal state of the animal, and environmental conditions also influence patch-leaving decisions. The demonstration of the existence of genetic variation in patch leaving mechanisms indicates that the way parasitoids respond to information is potentially through natural selection. Indeed, the patch leaving mechanisms observed in environments with different spatial distributions of hosts and other resources result in patch time allocation patterns that are more often in agreement with the predictions of deductive functional models. We show how most of our detailed knowledge about the responses of parasitoids to different stimuli stems from the use of powerful statistical tools (see also Chapter 18 by Wajnberg and Haccou). However, we also show the danger of ignoring critical influences. If the parasitoid responds to one or more cues not represented in the statistical model, erroneous conclusions on the effect of cues included in the model may be the result. This problem can be solved by a better understanding of parasitoid cognition. We need realistic models on how parasitoids integrate information from the environment with that of their internal state, to design more realistic statistical models. As parasitoids often compete with conspecifics, we review the theory on group foraging and stress the need for more empirical work on this topic. Understanding of the dynamics of group foraging and of dispersal decisions of individuals allows us to make a realistic link between individual behavior and population level processes.
When Parasitoid Males Make Decisions: Information Used when Foraging for Females
PLoS ONE, 2012
Optimal foraging models predict how an organism allocates its time and energy while foraging for aggregated resources. These models have been successfully applied to organisms such as predators looking for prey, female parasitoids looking for hosts, or herbivorous searching for food. In this study, information use and patch time allocation were investigated using male parasitoids looking for mates. The influence of the former presence of females in absence of mates and the occurrence of mating and other reproductive behaviours on the patch leaving tendency was investigated for the larval parasitoid Asobara tabida. Although males do not modify their patch residence time based on the number of females that visited the patch, they do show an increase in the patch residence time after mating a virgin female and performing courtship behaviour such as opening their wings. These results are in concordance with an incremental mechanism, as it has been described for females of the same species while foraging for hosts. The similarities between males and females of the same species, and the conditions under which such a patch-leaving decision rule is fitted are discussed. This is the first study describing an incremental effect of mating on patch residence time in males, thus suggesting that similar information use are probably driving different organisms foraging for resource, regardless of its nature.
Parasitoid Foraging and Learning
Chemical Ecology of Insects 2, 1995
The diminutive size of most parasitoids undoubtedly has limited their choice as subjects for behavioral study, despite their great diversity in lifestyles and reproductive strategies. The present chapter addresses their foraging behavior as influenced by learning. Most of their adult life female parasitoids search for host insects which, in tum, are under selection to avoid being found and devoured. This scenario sets the stage for the evolution of diverse hide-and-seek games played by parasitoids and their victims, most often herbivores. That parasitoids are successful in their quest for hosts is evidenced by the vast number of parasitoid species and their importance in insect management. 1.1. The Fixed Response Perspective The study of parasitoid foraging behavior entered a new era around the time of publication of Vinson's review (Vinson, 1984) on parasitoid-host relationships in the first edition of Chemical Ecology of 1nsects (Bell and Carde, 1984). Prior to that time, students of parasitoid foraging behavior mainly were involved in identifying and describing the steps of how an insect parasitoid finds a potential host in which to lay its eggs (e.g., Lewis et al. 1976). Although a major emphasis was placed on the importance of chemical stimuli in guiding this process, an impressive array of stimuli was revealed. In spite of this diversity in stimuli and behaviors involved, some generalizations were possible. For example, different searching phases, such as habitat location, host location, host examination, were distinguished. The importance of host-derived cues including frass, webbing, mandibular secretions, and scales of adult moths, in attracting and arresting parasitoids at a short distance also seemed a general phenomenon (Weseloh,
Knowing your habitat: linking patch-encounter rate and patch exploitation in parasitoids
Behavioral Ecology, 2004
According to optimal foraging theory, animals should decide whether or not to leave a resource patch by comparing the current profitability of the patch with the expected profitability of searching elsewhere in the habitat. Although there is abundant evidence in the literature that foragers in general are well able to estimate the value of a single resource patch, their decision making has rarely been investigated with respect to habitat quality. This is especially true for invertebrates. We have conducted experiments to test whether parasitic wasps adjust patch residence time and exploitation in relation to the abundance of patches within the environment. We used the braconid Asobara tabida, a parasitoid of Drosophila larvae, as our model species. Our experiments show that these wasps reduce both the residence time and the degree of patch exploitation when patches become abundant in their environment, as predicted by optimal foraging models. Based upon a detailed analysis of wasp foraging behavior, we discuss proximate mechanisms that might lead to the observed response. We suggest that parasitoids use a mechanism of sensitization and desensitization to chemicals associated with hosts and patches, in order to respond adaptively to the abundance of patches within their environment.
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.
Habitat assessment by parasitoids: mechanisms for patch use behavior
Behavioral Ecology, 2006
Animals foraging for patchily distributed resources may optimize their foraging decisions concerning the patches they encounter, provided that they base these decisions on reliable information about the profitability of the habitat as a whole. Females of the parasitoid Lysiphlebus testaceipes exploit aphid hosts, which typically aggregate in discrete colonies. We show here how betweencolony travel time and the number of aphids in previously visited colonies affect parasitoid foraging behavior. We first assumed that parasitoids use travel time and previous colony size to estimate a mean rate of fitness gain in the habitat and derived quantitative predictions concerning the effect of these two variables on patch residence time and patch-leaving rate of attack. We then tested these theoretical predictions in laboratory experiments in which female parasitoids were allowed to visit two successive colonies. As predicted, the observed residence time in the second colony increased with increasing travel time and decreasing size of the first colony. Patch-leaving rate of attack decreased with increasing travel time but was not affected by previous colony size. These results suggest that parasitoids use these two variables to assess habitat quality. However, discrepancies between the data obtained and quantitative predictions show that the effect of travel time on patch use may be more complex than assumed in our model.
Ecological Entomology, 2001
1. The foraging behaviour of the parasitoid wasp Halticoptera laevigata Thomson (Hymenoptera: Pteromalidae) was studied. This wasp attacks the ®rstinstar larvae of the fruit¯y Myoleja lucida Falle Ân (Diptera: Tephritidae) within honeysuckle Lonicera xylosteum L. (Caprifoliaceae) fruits. It was hypothesised that, to forage ef®ciently, wasps should be able to maintain a systematic or at least nonrandom search pattern on the level of the microhabitat, i.e. branches with fruits, and/or be able to recognise previously searched fruits. 2. Comparisons of observed patch visitation patterns on branches bearing uninfested fruits with expected values for systematic and random visitation patterns indicated that H. laevigata wasps visit patches randomly and do not avoid visiting host-free patches that they have visited previously. 3. While wasps did not alter their search effort on uninfested fruits searched previously by conspeci®cs, they searched for much shorter times and probed less frequently for hosts on uninfested fruits that they had searched previously. 4. The results indicate that H. laevigata wasps engage in partially systematic search and increase their search ef®ciency through the recognition of self-searched fruits. The reasons why partial rather than fully systematic search should be adaptive in this parasitoid are discussed.
Searching for Food or Hosts: The Influence of Parasitoids Behavior on Host-Parasitoid Dynamics
Theoretical population biology, 1997
A host-parasitoid system with overlapping generations is considered. The dynamics of the system is described by differential equations with a control parameter describing the behavior of the parasitoids. The control parameter models how the parasitoids split their time between searching for hosts and searching for non-host food. The choice of the control parameter is based on the assumption that each parasitoid maximizes the instantaneous growth rate of the number of copies of its genotype. It is shown that optimal individual behavior of parasitoids, with respect to time sharing between hosts and food searching, may have a stabilizing effect on the host-parasitoid dynamics.
When parasitoids deal with the spatial distribution of their hosts: consequences for both partners
Insect Science, 2018
Insect parasitoids developing inside hosts face a true challenge: hosts are scattered in the field and their localization and selection require the use of complex and sometime confusing information. It was assumed for a long time that small-brained organisms like parasitoids have evolved simple and efficient behavioral mechanisms, leading them to be adapted to a given ecological situation, e.g. the spatial distribution of hosts in the habitat. However, hosts are not static and their distribution may also vary through generations and within the life of parasitoid individuals. We investigated if and how parasitoids deal with such a spatial complexity in a mesocosm experiment. We used the Aphidius rhopalosiphi/Sitobion avenae parasitoid/host system to investigate if parasitoid females experiencing different host aggregation levels exhibit different foraging behaviors independently of the number of hosts in the environment. We showed that A. rhopalosiphi females exploited hosts more intensively both within and among patches at higher host aggregation levels. We discussed the adaptiveness of such behaviors in the light of evolution and biological control.