Marlène Goubault

• PhD
• Professor at University of Tours

BACKGROUND Bordeaux mixture is a copper‐based fungicide commonly used in vineyards to prevent fungal and bacterial infections in grapevines. However, this fungicide may adversely affect the entomological component, including insect pests. Understanding the impacts of Bordeaux mixture on the vineyard pest Lobesia botrana is an increasing concern in...

If the risk of larval competition is high and its consequence on offspring mortality is important, we expect female behavioural strategies favouring the survival of their offspring to be selected for. In parasitoids, hosts can be parasitized several times, in some cases by females of different species (i.e., multiparasitism). In solitary parasitoid...

• Pesticides can have unintentional effects on non-target species. • Pyriproxyfen is a juvenile hormone agonist used as endocrine disrupting insecticide. • We exposed beneficial parasitoid wasps to sublethal doses of pyriproxyfen. • It stimulated their fecundity and aggressive behavior. • The consequences on parasitoid and host populations remain t...

Ecdysteroids are a family of insect hormones that may play a role in modulating aggressive behavior in reproductive contexts. In Hymenoptera, the few studies investigating the link between ecdysteroid titers, reproduction and aggressiveness during contests concern solely eusocial species. Here, we explored whether ecdysteroid titers influenced fema...

Within the animal kingdom, individuals of the same species are often in conflict for access to certain resources. In solitary parasitoids, females can compete directly for access to a host that is an essential resource for their reproductive success. During this thesis, we investigated the factors that influence the display of agonistic behaviour a...

The 'challenge hypothesis' provides a predictive framework for how the social environment influences within-species variation in hormone titers. High testosterone levels are beneficial during reproduction and competition, but they also impose costs because they may suppress traits like parental care and immunity. As a result, the challenge hypothes...

Prior experience of fighting affects the outcome of subsequent contests, with prior winners being more likely to win and prior losers being more likely to lose a future encounter. These winner and loser effects have been shown in numerous species but have usually been tested in only one set of conditions. However, if such effects are not fixed but...

Intraspecific competition for indivisible resources can trigger the expression of agonistic behaviour in individuals of many animal species. Aggressiveness and conflict resolution may be influenced by the value individuals place on the resource (subjective resource value) but also by genetic relatedness between competitors. The ability to different...

In vertebrates, titers of androgens such as testosterone are known to upregulate aggressive behaviors associated with reproduction. In insects, juvenile hormone (JH) is a good candidate for studying the flexibility of insect endocrine responses because it has important effects on both reproductive processes and behavior. JH has a gonadotropic effec...

The objective of this experiment was to investigate the effect of the presence of an allospecific competitor on the final patch quality, i.e. the number of healthy, self-superparasitized and multiparasitized hosts remaining in the patch upon departure of the focal female. Conclusion (1) Do D. basalis females increase the probability of their offspr...

This study aims to understand whether D. basalis females’ behavioral strategies under interspecific direct competition with E. vuilleti vary according to their offspring survival chances (1) Do D. basalis females increase the probability of their offspring winning the larval competition by out-numbering the offspring of E. vuilleti (i.e. self-super...

Interspecific contest between Dinarmus basalis and Eupelmus vuilleti by RIHAB MOHAMA

Studying physical contests for indivisible resources is a major theme in behavioral ecology. Intensity (aggressiveness) and outcome of such contests may be influenced by individual abilities to gain and keep the resource (resource-holding potential, RHP), but also by the value they place in the resource (resource value, RV). Contestants can assess...

Insect reproduction is influenced by various external factors including temperature, a well studied constraint. We investigated to what extent different levels of sperm limitation of males exposed to different heat‐stresses (34°C and 36°C) affect females’ offspring production and sex allocation in Nasonia vitripennis. In this haplodiploid parasitoi...

Oviposition sites may be challenging and energetically costly to access for females in the presence of competitors contesting that resource. Additionally, oviposition sites may be difficult to reach, and penetrating a hard substrate can raise energy costs. In the seeddrilling parasitic wasp Eupelmus vuilleti, females actively fight with conspecific...

Competition for an indivisible resource is widespread in the animal kingdom and can lead to physical interactions between individuals. The value of the resource can also influence the aggressiveness and the outcome of the contest: the competitors fight more for a resource of good quality (real value of the resource) but also when they have been dep...

We use a game-theoretic model to explore whether volatile chemical (spiroacetal) emissions can serve as a weapon of rearguard action. Our basic model explores whether such emissions serve as a means of temporary withdrawal, preventing the winner of the current round of a contest from translating its victory into permanent possession of a contested...

Lekking males aggregate to attract females and contribute solely to egg fertilization, without any further parental care. Evolutionary theory therefore predicts them to be non-choosy towards their mates, because any lost mating opportunities would outweigh the benefits associated with such preferences. Nevertheless, due to time costs, the productio...

Host plants possibly represent the strongest selection pressure for the evolution of reproductive traits in phytophagous insects. In a first part of this chapter, we review how plant quality affects both female and male life history traits and their respective reproductive success, and how the production and transfer to females of male sperm and as...

Precopulatory mate guarding is often observed when the availability of female gametes is limited. However, in the lek-mating lesser wax moth, Achroia grisella, this behaviour would result from a constraint on the release of male ejaculate. After a recent mating, males can quickly take hold of, and thereby monopolize, a female until they are able to...

competitive environment ejaculate size lek mating system Lepidoptera postcopulatory sexual selection sperm competition risk sperm economy strategic ejaculation Sperm competition has been demonstrated to be a strong selective force shaping male mating behaviours and ejaculate traits, particularly in highly polyandrous species. Its effect, however, i...

In recent years, several studies have shown a decline in reproductive success in males in both humans and wildlife. Research on male fertility has largely focused on vertebrates, although invertebrates constitute the vast majority of terrestrial biodiversity. The reduction of their reproductive capacities due to environmental stresses can have stro...

The presence of competitors may affect the pay-off of individuals' foraging strategies. They should therefore modify their resource exploitation decisions accordingly. In such a direct competition situation, theory predicts that individuals should stay longer on a resource patch than when foraging alone. However, models predicting patch residence t...

In species in which males provide females with nuptial gifts, females can benefit from choosing mates offering the larger or higher quality donation. The existence of such preferences assumes that females can reliably assess a male's gift before mating. However, in certain species, for example most bushcrickets, prior, direct assessment of the nupt...

Contests are an important aspect of the lives of diverse animals, from sea anemones competing for space on a rocky shore to fallow deer stags contending for access to females. Why do animals fight? What determines when fights stop and which contestant wins? Addressing fundamental questions on contest behaviour, this volume presents theoretical and...

The insect order Hymenoptera is speciose, diverse and common. Many wasps, bees and ants are well known for their ability, and propensity, to engage in agonistic interactions via biting and stinging (chemical injection), and may also interact using chemical deposition and volatile chemical release. Such behaviours are often exhibited during acquisit...

Biological control of bruchid beetles, Callosobruchus maculatus (Fabricius) (Coleoptera: Bruchidae), infesting cowpea seeds, Vigna unguiculata (L.) Walpers (Fabaceae), can be performed via augmentative releases of Dinarmus basalis Rondani (Hymenoptera: Pteromalidae) parasitoid wasps. Females of the latter species are therefore likely to experience...

When two species exploit the same ecological niche, interspecific competition may lead to the exclusion of one of them. For the two species to co-exist, resource exploitation strategies developed by both species must somehow counter-balance each other. Eupelmus vuilleti and Dinarmus basalis are two solitary parasitoid species exploiting the same ho...

Contests for indivisible resources are often settled on the basis of the asymmetry that exists between contestants in their ownership status: Owners (i.e., individuals already possessing a resource) usually retain the resource when facing intruder competitors. This owner advantage is predicted to be more pronounced as the asymmetry in ownership sta...

The experience of a previous conflict can affect animals' performance during a later contest: a victory usually increases and a defeat usually decreases the probability of winning a subsequent conflict. These winner and loser effects could result from a reassessment by contestants of their perceived fighting abilities. Game-theoretic models based o...

Already parasitized hosts are often of poorer quality than healthy hosts. It is therefore usually advantageous for parasitoid females to recognize and reject them. Parasitized hosts can be identified on the basis of various physical or chemical marks present on the surface or inside the hosts or their surroundings in the case of concealed host. Her...

When 2 species exploit the same limiting resource, interspecific competition may lead to the exclusion of one of them. For the 2 species to coexist, resource exploitation strategies exhibited by both species must somehow counterbalance each other. Eupelmus vuilleti and Dinarmus basalis are 2 solitary parasitoid species exploiting the same hosts (la...

Although animal contests for resources are often settled in favour of individuals with the greatest fighting abilities, other factors, such as those affecting the value that contestants place on the resource, can also influence contest resolution and aggressiveness. For example, competitors should fight more fiercely for access to larger than small...

Models of dyadic contests for indivisible resources have predicted that the owner--intruder role distinction can suffice as a cue for evolutionarily stable resolution. This outcome may be "common sense" (prior owners retain the resource) or counterintuitively "paradoxical" (the intruder takes over), but the most recent models predict paradoxes to b...

The structures of volatile chemicals released by parasitic wasps in the family Bethylidae are shown to correspond to the subfamily to which the species belong. Species in the Epyrinae release skatole (3-methylindole) and species in the Bethylinae release a spiroacetal (2-methyl-1,7-dioxaspiro [5.5]undecane): these compounds are chemically very diff...

Behavioural studies often need to employ marking techniques to identify and track individuals. Marks ideally have no influence on behaviour or fitness of marked individuals or on the organisms with which they interact. A newly developed internal marking technique uses deuterium to manipulate the chemical emissions of bethylid wasps that are parasit...

Parent investment theory predicts that parents should adjust their investment in offspring defence according to offspring value. For instance, parents should protect older, more valuable, offspring more intensively than younger offspring against a given risk of mortality. The benefits of protection may, however, vary with offspring age and parents...

Understanding the size of clutches produced by only one parent may require a game-theoretic approach: clutch size may affect offspring fitness in terms of future competitive ability. If larger clutches generate smaller offspring and larger adults are more successful in acquiring and retaining resources, clutch size optima should be reduced when the...

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...

Animal interactions often involve chemical exchange but simultaneous evaluation of chemistry and behaviour has been problematical. Here we report findings from a novel method, atmospheric pressure chemical ionization-mass spectrometry (APCI-MS) coupled with manipulation of molecular-mass achieved by rearing organisms on deuterium-enhanced nutrients...

The optimal residence time of a forager exploiting a resource patch in the absence of competitors has been much studied since the development of the marginal value theorem. However, several foragers are frequently observed exploiting the same patch simultaneously, and patch residence time has been surprisingly little studied in such competitive sit...

Host acceptance decision in parasitic wasps depends strongly on the parasitism status of the encountered host. In solitary species, a host allows the development of only a single parasitic larva, and then any oviposition in an already parasitized host leads to larval competition and to potential loss of offspring. The ability of parasitoids to disc...

In solitary parasitoid species, superparasitism incurs a high cost because only one individual can emerge per host. While avoiding already-parasitized hosts seems advantageous, it requires an ability to discriminate between parasitized and unparasitized hosts. The ability to discriminate can be based on physical or chemical cues or signal associate...

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....

Optimal Foraging Theory predicts that parasitoid females should optimize their host selection to maximize their lifetime fitness gain and parasitize the most profitable hosts. In particular, in solitary parasitoids, females should avoid superparasitism, at least when sufficient unparasitized hosts are available. However, when unparasitized hosts ar...

In solitary parasitoids, only one individual can emerge per host. Therefore, females should reject already parasitized hosts. However, when unparasitized hosts are scarce, superparasitism becomes advantageous and females should choose hosts that offer the best survival chances to their progeny, which depend on the developmental stage of the first p...

Résumé Chez les parasitoïdes solitaires, un seul individu émerge par hôte, aussi les femelles devraient rejeter ceux préalablement parasités. Cependant, lorsque les hôtes sains sont rares, le superparasitisme devient avantageux et les femelles devraient choisir ceux offrant les meilleures chances de survie à leurs descendants ce qui dépend du stade...