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International audience; The current study extends the faunistic survey ofTrichogrammaspecies parasitizing ECB to all agricultural growing regions in Serbia. Specimens ofTrichogrammawere reared from parasitized egg masses of ECB collected from field-grown corn and pepper crops. The number of egg masses parasitized varied by location. Using sequences of mitochondrial cytochrome oxidase I (COI) gene, we examined intra and interspecific variation inTrichogrammaparasitizing the ECB egg masses. Seventy specimens were successfully sequenced of which, 65 were identified asT. brassicae. The remaining five were identified asT. evanescens, and this second species was only collected from pepper.

Uncertainty about the taxonomic status and the specificity of a species commonly prevent its consideration as a candidate for biological control of pest organisms. Here we use a combination of molecular analysis and crossing experiments to gather evidence that the parasitoid wasp Ganaspis brasiliensis, a candidate for biological control of the invasive spotted wing drosophila Drosophila suzukii, is a complex of at least two cryptic species. Complementary experiments demonstrate that individuals from one genetic group readily parasitize several drosophila species regardless of their food source while individuals from the other one are almost exclusively specific to larvae feeding in ripening fruits. Because only D. suzukii attacks ripening fruits in its area of invasion, parasitoids from this second group appear to be well suited as a biological control agent. Our study demonstrates the need for a combination of biosystematics with biological and ecological investigations for the development of safe and efficient biological control programs.

International audience; The spotted wing Drosophila, Drosophila suzukii (Ds), became a major economic pest for fruit production since its establishment in Europe and America. Among potential control methods, only classical biological control appears to be a mean of sustainably regulating Ds in both cultivated and natural habitats. In the frame of risk assessment, pre-release surveys were carried out in a restricted but highly heterogeneous area in the south-east of France using traps and deliberate field exposures of Ds and D. melanogaster larvae/pupae. Although Ds abundance varied according to sampling methods, it was found to be pervasive and to produce offspring and adults in most conditions (spatial and seasonal). Its main limits are some specific abiotic conditions (i.e., desiccation) as well as interspecific competition. Indeed, Ds mostly co-occurred with D. busckii and D. hydei, probably due to common phenology and/or ecological requirements. These two species thus deserve more attention for risk assessment. The main indigenous parasitoids collected belonged to two pupal species, Trichopria cf drosophilae and Pachycrepoideus vindemmiae, but their presence was observed late in the autumn and mainly in cultivated areas. Results are discussed in a comparison of the methodological approaches for monitoring Drosophilids and the benefits-risks assessment of classical biological control.

Inbreeding depression is a major concern in almost all human activities relating to plant and animal breeding. The biological control of pests with natural enemies is no exception, because populations of biocontrol agents experience a series of bottlenecks during importation, rearing, and introduction. A classical biological control program for the Comstock mealybug Pseudococcus comstocki (Hemiptera: Pseudococcidae) was initiated in France in 2008, based on the introduction of an exotic parasitoid, Allotropa burrelli Mues. (Hymenoptera: Platygastridae), a haplodiploid parasitoid imported from Japan. We evaluated the sensitivity of A. burrelli to inbreeding, to optimize rearing and release strategies. We compared several morphological and life‐history traits between the offspring of siblings and the offspring of unrelated parents. We took into account the low level of genetic variability due to the relatively small size of laboratory‐reared populations by contrasting two types of pedigree: one for individuals from a strain founded from a single field population, and the other generated by hybridizing individuals from two strains founded from two highly differentiated populations. Despite this careful design, we obtained no evidence for a negative impact of inbreeding on laboratory‐reared A. burrelli. We discussed the results in light of haplodiploid sex determination and parasitoid mating systems, and classical biological control practices.

International audience; Classical biological control-the introduction of exotic species to permanently control pests-offers an applied framework to test ecological and evolutionary hypotheses derived from invasion biology. One such hypothesis is that intraspecific hybridization can facilitate invasions because hybrids express higher phenotypic mean and/or variance than their parents. We tested this hypothesis using the parasitoid wasp Psyttalia lounsburyi, a candidate biocontrol agent for the olive fly Bactrocera oleae. Under laboratory conditions, we found marked differentiations between two populations of wasps, from South Africa and Kenya, in terms of life history strategies. South African females were better reproducers than Kenyan females, but the opposite was observed for males. Reaction norms showed different effects of developmental temperature on fecundity depending on the genotype. However, neither heterosis nor hybrid breakdown were observed. Hence, in this system, sex-specific effects of hybridization and genotype-by-environment interactions jeopardize any straightforward prediction on the fitness of hybrids. Therefore, our paper contributes to tone down the hybrid advantage hypothesis in invasion biology.

International audience; Numerous arthropod species are genetically differentiated across their distribution area. Diversifying the geographical origins of a biocontrol agent species can be used to favour their perennial establishment by the sampling of pre-adapted genotypes and/or the production of new genotypes through hybridization. Hybridization can be nevertheless challenged by reproductive isolations induced by some common microbial endosymbionts. In this study, we aimed at characterizing (i) the genetic diversity of six populations of Psyttalia lounsburyi (Hymenoptera: Braconidae), a candidate biocontrol agent of the olive fruit fly Bactrocera oleae (Diptera: Tephritidae) and (ii) the diversity of their Wolbachia endosymbionts. Both mitochondrial and microsatellite markers evidence clustering between the South African population and several Kenyan/Namibian populations. The survey of the Wolbachia also distinguished two main variants with a spatial heterogeneity in the infection status. All these results are discussed in the context of the use of these P. lounsburyi populations for hybridization and further field releases.

Drosophila suzukii (the spotted-wing Drosophila) appears to be unsuitable for the development of most Drosophila larval endoparasitoids, be they sympatric or not. Here, we questioned the physiological bases of this widespread failure by characterizing the interactions between D. suzukii and various parasitoid species (Asobara japonica, Leptopilina boulardi, Leptopilina heterotoma and Leptopilina victoriae) and comparing them with those observed with D. melanogaster, a rather appropriate host. All parasitoids were able to oviposit in L1 and L2 larval stages of both hosts but their propensity to parasitize was higher on D. melanogaster. A. japonica and, to a much lesser extent, L. heterotoma, were the two species able to successfully develop in D. suzukii, the failure of the parasitism resulting either in the parasitoid encapsulation (notably with L. heterotoma) or the host and parasitoid deaths (especially with L. boulardi and L. victoriae). Compared to D. melanogaster, encapsulation in D. suzukii was strongly delayed and led, if successful, to the production of much larger capsules in surviving flies and, in the event of failure, to the death of both partners because of an uncontrolled melanization. The results thus revealed a different timing of the immune response to parasitoids in D. suzukii compared to D. melanogaster with a lose-lose outcome for parasitoids (generally unsuccessful development) and hosts (high mortality and possible reduction of the fitness of survivors). Finally, these results might suggest that some European endoparasitoids of Drosophila interact with this pest in the field in an unmeasurable way, since they kill their host without reproductive success.

Background The ecological differentiation of insects with parasitic life-style is a complex process that may involve phylogenetic constraints as well as morphological and/or behavioural adaptations. In most cases, the relative importance of these driving forces remains unexplored. We investigate here this question for the “Eupelmus urozonus species group” which encompasses parasitoid wasps of potential interest in biological control. This was achieved using seven molecular markers, reliable records on 91 host species and a proxy of the ovipositor length. Results After using an adequate partitioning scheme, Maximum likelihood and Bayesian approaches provide a well-resolved phylogeny supporting the monophyly of this species group and highlighting its subdivision into three sub-groups. Great variations of both the ovipositor length and the host range (specialist versus generalist) were observed at this scale, with these two features being not significantly constrained by the phylogeny. Ovipositor length was not shown as a significant predictor of the parasitoid host range. Conclusions This study provides firstly the first evidence for the strong lability of both the ovipositor’s length and the realised host range in a set of phylogenetically related and sympatric species. In both cases, strong contrasts were observed between sister species. Moreover, no significant correlation was found between these two features. Alternative drivers of the ecological differentiation such as interspecific interactions are proposed and the consequences on the recruitment of these parasitoids on native and exotic pests are discussed. Electronic supplementary material The online version of this article (doi:10.1186/s12862-015-0571-2) contains supplementary material, which is available to authorized users.

International audience; Environmental variation is classically expected to affect negatively population growth and to increase extinction risk, and it has been identified as a major determinant of establishment failures in the field. Yet, recent theoretical investigations have shown that the structure of environmental variation and more precisely the presence of positive temporal autocorrelation might alter this prediction. This is particularly likely to affect the establishment dynamics of biological control agents in the field, as host–parasitoid interactions are expected to induce temporal autocorrelation in host abundance. In the case where parasitoid populations display overcompensatory dynamics, the presence of such positive temporal autocorrelation should increase their establishment success in a variable environment. We tested this prediction in laboratory microcosms by introducing parasitoids to hosts whose abundances were manipulated to simulate uncorrelated or positively autocorrelated variations in carrying capacity. We found that environmental variability decreased population size and increased parasitoid population variance, which is classically expected to extinction risk. However, although exposed to significant environmental variation, we found that parasitoid populations experiencing positive temporal autocorrelation in host abundance were more likely to persist than populations exposed to uncorrelated variation. These results confirm that environmental variation is a key determinant of extinction dynamics that can have counterintuitive effects depending on its autocorrelation structure.

Phenotypic plasticity and genotype-by-environment interactions are usually studied by testing environmental factors separately. However, several environmental factors may vary simultaneously across the geographic range of a species, and thus interact to drive phenotypic and genotypic evolution. Here, we address the question of the interaction between two environmental factors in the case of a koinobiont parasitoid of Drosophila, Leptopilina heterotoma (Hymenoptera: Figitidae). Using two allopatric parasitoid lines, we analysed the joint effect of developmental temperature and host species on two major fitness components (pre-imaginal survival and fecundity) of emerged parasitoids. Our results indicate that both environmental factors strongly interact to shape the parasitoid phenotype. Moreover, complex genotype-by-environment interactions appeared that can even invert the relative fitness of the two parasitoid lines.

We have developed 21 dinucleotide repeat microsatellite loci from African populations of Psyttalia lounsburyi (Silvestri) (Hymenoptera: Braconidae), a parasitoid wasp of the olive fruit fly, as part of a study assessing the role of introgression/hybridization in the success of a biological control introduction. We proposed suitable conditions for polymerase chain reaction multiplexing. All 21 loci were polymorphic with two to 21 alleles per locus within the Kenyan and South African populations tested. Most of them were successfully amplified in two other Psyttalia species.

In plants, membrane-bound receptor kinases are essential for developmental processes, immune responses to pathogens and the establishment of symbiosis. We previously identified the Arabidopsis (Arabidopsis thaliana) receptor kinase IMPAIRED OOMYCETE SUSCEPTIBILITY1 (IOS1) as required for successful infection with the downy mildew pathogen Hyaloperonospora arabidopsidis. We report here that IOS1 is also required for full susceptibility of Arabidopsis to unrelated (hemi)biotrophic filamentous oomycete and fungal pathogens. Impaired susceptibility in the absence of IOS1 appeared to be independent of plant defense mechanism. Instead, we found that ios1-1 plants were hypersensitive to the plant hormone abscisic acid (ABA), displaying enhanced ABA-mediated inhibition of seed germination, root elongation, and stomatal opening. These findings suggest that IOS1 negatively regulates ABA signaling in Arabidopsis. The expression of ABA-sensitive COLD REGULATED and RESISTANCE TO DESICCATION genes was diminished in Arabidopsis during infection. This effect on ABA signaling was alleviated in the ios1-1 mutant background. Accordingly, ABA-insensitive and ABA-hypersensitive mutants were more susceptible and resistant to oomycete infection, respectively, showing that the intensity of ABA signaling affects the outcome of downy mildew disease. Taken together, our findings suggest that filamentous (hemi)biotrophs attenuate ABA signaling in Arabidopsis during the infection process and that IOS1 participates in this pathogen-mediated reprogramming of the host.

Parasitoids and their hosts are linked by intimate and harmful interactions that make them well suited to analyze fundamental ecological and evolutionary processes with regard to life histories evolution of parasitic association. Drosophila aspects of what parasitoid Hymenoptera have become model organisms to study aspects that cannot be investigated with other associations. These include the genetic bases of fitness traits variations, physiology and genetics of resistance/virulence, and coevolutionary dynamics leading to local adaptation. Recent research on evolutionary ecology of Drosophila parasitoids were performed mainly on species that thrive in fermenting fruits (genera Leptopilina and Asobara). Here, we review information and add original data regarding community ecology of these parasitoids, including species distribution, pattern of abundance and diversity, host range and the nature and intensity of species interactions. Biology and the evolution of life histories in response to habitat heterogeneity and possible local adaptations leading to specialization of these wasps are reported with special emphasis on species living in southern Europe. We expose the diversity and intensity of selective constraints acting on parasitoid life history traits, which vary geographically and highlight the importance of considering both biotic and abiotic factors with their interactions to understand ecological and evolutionary dynamics of host-parasitoid associations.

Drosophila species are attacked by a number of parasitoid wasps, which constitute an important factor of population regulation. Since Drosophila melanogaster and Drosophila simulans share common parasitoid species, their ecology and evolution can hardly be understood without considering parasitoids. After a short review of data available on Drosophila-parasitoid interactions involving D. melanogaster and D. simulans as hosts, we report field and laboratory experiments investigating the ecological role of Leptopilina parasitoids in Drosophila communities of southern France. Seasonal survey of species abundance shows that strong interspecific interactions occur at both tropic levels. D. simulans progressively replaces D. melanogaster in southern areas suggesting competitive displacement. Parasitoids are responsible for very high Drosophila mortality (up to 90% in some fruits). Field data emphasize the importance of selective pressure that parasitoids exert on Drosophila communities. The two Leptopilina parasites (L. heterotoma and L. boulardi) have different local abundances, which vary in time, and they also compete for hosts. We show that parasitoids can mediate the coexistence of D. melanogaster and D. simulans in the laboratory, and thus may contribute to their puzzling coexistence in the field. Conversely, hosts exert selective pressures on parasitoids, and development on either D. melanogaster or D. simulans strongly affects fitness of adult wasps in a temperature-dependent fashion. Local variation in host species abundance and diversity could thus account for the genetic differentiation we observed in one parasitoid species. Despite laboratory studies cannot fully explain complex field situations, it is clear that the ecology and evolution of Drosophila populations and communities, especially D. melanogaster and D. simulans, are strongly constrained by parasitoids, which should receive more attention.