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International audience; Augmentative biological control is based on the repeated introduction of mass-produced biological control agents as predators or parasitoids with the aim of temporarily controlling or even eradicating pest populations. The different augmentative strategies form a continuum ranging from preventive releases of small numbers of natural enemies prior to the arrival of the pests for a delayed impact (inoculation) to intense, short-term mass releases for a quick and drastic impact on the pest population (inundation). These strategies may also be combined with practices that aim to favour the individual fitness and/or the population establishment of the biological control agents. After briefly reviewing the history of such practices, this chapter explores different challenges currently faced by augmentative biological control linked to the production of biocontrol agents, the underlying business models and the potential existence of non-target effects. Finally, different ways to improve augmentative biological control are investigated, from better selection of biocontrol agent strains to innovations in rearing conditions or supplementation of resources to support the introduced natural enemies. The need to better understand the population dynamics at play or the possible combination of augmentative biological control with entomovectoring techniques are also discussed.

International audience; Les caractéristiques de Drosophila suzukii (fécondité, plantes-hôtes, nombre de générations…) en font un ravageur difficile à maîtriser en cultures fruitières, en particulier en verger de cerisier et en cultures de fruits rouges (fraise, framboise). Les solutions actuelles ne donnent pas entièrement satisfaction, du fait de contraintes techniques ou économiques. La lutte biologique permettrait de diminuer la pression du ravageur sur le territoire. Cet article précise l’avancée de recherches pour une lutte biologique par acclimatation, qui se définit par l’introduction d’un auxiliaire exotique provenant de la même zone d’origine que le ravageur-cible, dans le but de son établissement permanent et d’un contrôle durable du ravageur. Après avoir identifié les ennemis naturels de Drosophila suzukii dans sa zone d’origine (parasitoïdes des genres Asobara, Ganaspis et Leptopilina), les programmes ont permis d’évaluer finement les candidats potentiels au laboratoire. L’espèce Ganaspis cf. brasiliensis, et plus particulièrement la population G1 (« groupe moléculaire 1 »), s’avère prometteuse et une demande d’introduction dans l’environnement devrait être faite prochainement.

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.

National audience; In response to the introduction and spread of the chestnut gall wasp Dryocosmus kuriphilus Yasumatsu (Hymenoptera: Cynipidae) in metropolitan France, including Corsica, the exotic parasitoid Torymus sinensis Kamijo (Hymenoptera: Torymidae) was deliberately introduced in more than 50 locations covering most of the areas of chestnut production. To test the impact of propagule pressure (i.e., the number and size of introductions) on establishment success and post-release dynamics, the introductions were done according to three experimental modalities: (1) a single introduction of 100 females, (2) two sequential introductions of 50 females, or (3) a single introduction of 1000 females. Post-release surveys demonstrated a very high local establishment of T.sinensis, regardless of the introduction modality. Post-introduction dynamics were found to follow a two-phase process. First, early dynamics were characterized by an exponential growth of T.sinensis populations without a significant decrease in D.kuriphilus populations. Later, middle-term dynamics indicated a global decrease in both D.kuriphilus and T.sinensis populations. Quite surprisingly, propagule pressure had a limited effect on post-introduction dynamics, with a lasting demographic advantage for the largest introductions, but no influence of the number of introductions. Finally, site connectivity had a positive effect on T.sinensis population size, suggesting successful colonization and establishment at a wide spatial scale beyond the introduction sites. In addition, we observed that some T.sinensis exhibited a very short developmental time compared to the majority of the emerged individuals, which may be interpreted as a diversified bet hedging strategy against environmental stochasticity. These findings confirm the strong potential of T.sinensis for successful establishment and sustainable control of the chestnut gall wasp in Europe.

International audience; We performed no-choice tests to study the host range of the parasitoid Allotropa burrelli (Muesebeck) (Hymenoptera: Platygastridae) for use against the Comstock mealybug, Pseudococcus comstocki (Kuwana) (Hemiptera: Pseudococcidae), in Southern France. We tested three Pseudococcidae species as potential non-target hosts: two species from the same genus (Pseudococcus longispinus and Pseudococcus viburni) and Planococcus citri. Allotropa burrelli did not parasitize any of the non-target mealybug species tested. No attempt of oviposition was recorded for the three species tested during the first 20min of parasitoid release and no parasitism occurred in 6-8hr of exposure of the mealybugs to the parasitoid.

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 rise of the Asian chestnut gall wasp Dryocosmus kuriphilus in France has benefited the native community of parasitoids originally associated with oak gall wasps by becoming an additional trophic subsidy and therefore perturbing population dynamics of local parasitoids. However, the successful biological control of this pest has then led to significant decreases in its population densities. Here we investigate how the invasion of the Asian chestnut gall wasp Dryocosmus kuriphilus in France and its subsequent control by the exotic parasitoid Torymus sinensis has impacted the local community of native parasitoids.We explored 5 years of native community dynamics within 26 locations during the rise and fall of the invasive pest. In an attempt to understand how mechanisms such as local extinction or competition come into play, we analyzed how the patterns of co-occurrence between the different native parasitoid species changed through time.Our results demonstrate that native parasitoid communities experienced increased competition as the D. kuriphilus levels of infestation decreased. During the last year of the survey, two alternative patterns were observed depending on the sampled location: either native parasitoid communities were represented by an extremely limited number of species occurring at low densities, in some cases no native parasitoid species at all, or they were dominated by one main parasitoid: Mesopolobus sericeus. These two patterns seemed to correlate with the habitat type, M. sericeus being more abundant in semi-natural habitats compared to agricultural lands, the former known to be natural reservoirs for native parasitoids. These results highlight how the “boom-and-bust” dynamics of an invasive pest followed by successful biological control can deeply alter the structure of native communities of natural enemies.This article has been peer-reviewed and recommended by Peer Community in Zoologyhttps://doi.org/10.24072/pci.zool.100004

National audience

Drosophila suzukii is an invasive fly of East Asian origin that has become a serious fruit pest worldwide. Classical biological control through the introduction of parasitoids from Asia could help reduce populations of D. suzukii in invaded regions. Little is known about the native parasitoids of the fly in Asia. Therefore, surveys for larval parasitoids of D. suzukii were carried out in China and Japan between 2015 and 2017. Parasitoids of D. suzukii and other fruit-inhabiting drosophilids (D. pulchrella and D. subpulchrella) that are probably attacked by the same parasitoid complex were found in four Chinese provinces and four Japanese prefectures. Larval parasitoids were obtained at most sites where D. suzukii was found, with parasitism varying from 0.0 to 75.6%. At least eight parasitoid species were reared. The most abundant and frequent parasitoids were the Figitidae Ganaspis cf. brasiliensis and Leptopilina japonica, but another Leptopilina species and at least five Braconidae species belonging to the genera Areotetes, Asobara and Tanycarpa were obtained in low numbers. Due to its likely restricted host range, the most promising parasitoid for biological control is Ganaspis cf. brasiliensis. However, its exact specificity and taxonomic status require future research.

Sampling of Trichogramma species on Cucurbitaceae and associated plants in Martinique : a first step towards biological control (Hymenoptera, Trichogrammatidae). Cucurbitaceae represent an important part of the vegetable production in Martinique. One of the main pest on these crops is the melonworm, Diaphana hyalinata. With the final objective of defining sustainable strategies for the management of this pest with low quantities of pesticides, an inventory of the Trichogramma egg parasitoids was conducted in 2014 on the island. This survey was implemented using two methods, the use of sentinel eggs of Ephestia kuehniella and collections of natural egg clutches. Based on molecular information, two species were finally observed, Trichogramma pretiosum Riley, 1879, and T. chilonis Ishii, 1941. Based on this survey, a strain of T. pretiosum was mass-reared using Corcyra cephalonica and used for first promising inundative releases., Les Cucurbitacées représentent une part importante de la production maraîchère de Martinique. Un des principaux ravageurs de ces cultures est la Pyrale des cucurbitacées, Diaphania hyalinata. Avec pour objectif final la définition de stratégies de gestion économe en produits phytosanitaires, un inventaire des parasitoïdes oophages du genre Trichogramma a été réalisé en novembre 2014 sur l’île de la Martinique. Cet échantillonnage a été réalisé selon deux méthodes, l’utilisation d’oeufs-sentinelles d’Ephestia kuehniella et la recherche de pontes naturelles. Au final, deux espèces ont été identifiées sur une base moléculaire, Trichogramma pretiosum Riley, 1879, et T. chilonis Ishii, 1941. Suite à cet échantillonnage, T. pretiosum a été mis en élevage sur un hôte de substitution, Corcyra cephalonica, et utilisé pour des premiers lâchers inondatifs prometteurs., Dumbardon-Martial Thierry, Lucas Pierre-Damien, Warot Sylvie, Ris Nicolas, Groussier Géraldine. Recherche d’espèces du genre Trichogramma sur Cucurbitacées cultivées et plantes associées en Martinique en vue du développement de méthodes de lutte biologique (Hymenoptera, Trichogrammatidae). In: Bulletin de la Société entomologique de France, volume 123 (4),2018. pp. 401-410.

The effects of some abiotic (maternal photoperiod and offspring developmental temperature) and biotic (host quality during both maternal and offspring generations) factors on diapause induction were investigated for two sympatric strains of Trichogramma brassicae Bezdenko (Hym: Trichogrammatidae) differing by infection status with regard to Wolbachia. The mode of reproduction, developmental temperature, maternal photoperiod and the quality of the host significantly affected diapause induction. The highest percentage of diapausing individuals were observed with the sexual strain reared at 14 °C using a “high quality” host and after a long photophase during the maternal generation. Environment-by-Environment, as well as Genotype-by-Environment interactions, was observed. All these patterns were discussed with the goal of providing relevant protocols for the commercial mass-rearing of such biocontrol agents. A successful diapause in beneficial insects could affect the efficiency of mass rearing by increasing the duration of storage conditions based on a high percent emergence and providing a large number of individuals at the appropriate time in the field season.

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.

We report here the first observation of Zaprionus indianus Gupta in mainland France. Five specimens of both sexes were trapped in a liquid vinegar bait in Cap d’Antibes (French Riviera) and their taxonomic identification was then performed by morphologi-cal and molecular analysis. Z. indianus is recognized as a fig pest in the invaded American countries, and it could pose economic problems in this new location since figs are also grown in European Mediterranean areas. This Drosophilid species is on the EPPO pest quarantine list. Its spread and possible permanent establishment in South France should thus be monitored in the next years to assess possible agricultural damages.

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.

Mealybugs (Hemiptera: Pseudococcidae) are major pests of a wide range of crops and ornamental plants worldwide. Their high degree of morphological similarity makes them difficult to identify and limits their study and management. We aimed to identify a set of markers for the genetic characterization and identification of complexes of taxa in the Pseudococcidae. We surveyed and tested the genetic markers used in previous studies and then identified new markers for particularly relevant genomic regions for which no satisfactory markers were available. We tested all markers on a subset of four taxa distributed worldwide. Five markers were retained after this first screening: two regions of the mitochondrial cytochrome oxidase I gene, 28S-D2, the entire internal transcriber space 2 locus and the rpS15-16S region of the primary mealybug endosymbiont Tremblaya princeps. We then assessed the utility of these markers for the characterization and identification of 239 samples from 43 sites in France and Brazil. The five markers studied (i) successfully distinguished all species identified by morphological examination, (ii) disentangled complexes of species by revealing intraspecific genetic variation and identified a set of closely related taxa for which taxonomic status requires clarification through further studies, and (iii) facilitated the inference of phylogenetic relationships between the characterized taxa.

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.

WOS: 000378865200032 PubMed ID: 27362639 Pseudococcus comstocki (Hemiptera: Pseudococcidae) is a mealybug species native to Eastern Asia and present as an invasive pest in northern Italy and southern France since the start of the century. It infests apple and pear trees, grapevines and some ornamental trees. Biocontrol programmes against this pest proved successful in central Asia and North America in the second half of the 20th century. In this study, we investigated possible bio-control agents against P. comstocki, with the aim of developing a biocontrol programme in France. We carried out systematic DNA-barcoding at each step in the search for a specialist parasitoid. First we characterised the French target populations of P. comstocki. We then identified the parasitoids attacking P. comstocki in France. Finally, we searched for foreign mealybug populations identified a priori as P. comstocki and surveyed their hymenopteran parasitoids. Three mealybug species (P. comstocki, P. viburni and P. cryptus) were identified during the survey, together with at least 16 different parasitoid taxa. We selected candidate biological control agent populations for use against P. comstocki in France, from the species Allotropa burrelli (Hymenoptera: Platygastridae) and Acerophagus malinus (Hymenoptera: Encyrtidae). The coupling of molecular and morphological characterisation for both pests and natural enemies facilitated the programme development and the rejection of unsuitable or generalist parasitoids. French "Agence Nationale de la Recherche"French National Research Agency (ANR) [ANR-10-JCJC-1708 BICORAMICS]; EUEuropean Union (EU) [324475 COLBICS, 265865 PURE]; Turkey-France Cooperation grant CNRS-TUBITAK; INRA Plant Health and Environment DivisionInstitut National de la Recherche Agronomique (INRA) This work was funded by the French "Agence Nationale de la Recherche" (grant ANR-10-JCJC-1708 BICORAMICS), by the EU Seventh Framework Programme (grants Marie-Curie IAPP #324475 COLBICS and KBBE #265865 PURE), by a Turkey-France Cooperation grant CNRS-TUBITAK, and by the INRA Plant Health and Environment Division. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

9 páginas, 4 figuras, 1 tabla, Armored scales (Hemiptera: Diaspididae) are important pests in citrus orchards worldwide. Augmentative releases of Aphelinidae wasps (Hymenoptera) have been performed in Corsica, France to control the California Red Scale (Aonidiella aurantii (Maskell, 1879)) and the arrowhead scale (Unaspis yanonensis (Kuwana, 1923)), but biological control of armored scales requires the identification of their parasitoids to evaluate their potential as biological control agents. In order to circumvent this issue, parasitoids emerging from four armored scale species were characterized through DNA barcoding. All the parasitoids identified belong to the Aphelinidae (Hymenoptera) and included a total of five Aphytis (including A. melinus), four Encarsia (including cryptic species) and one Ablerus (hyperparasitoid) species. Host-specificity was found to be strong among primary parasitoids, with Encarsia inquirenda Silvestri, 1930 and an unidentified Encarsia being the sole taxa able to parasitize the two subfamilies (Aspidiotinae and Diaspidinae)., This work was funded by the ONEMA through the ECOPHYTO program of the Cors’Aphy Project. MC and FP received financial support from the Marie Curie FP7 IAPP Project ‘‘Colbics’’ #324475. FP also acknowledges support by the project CHALLENGEN (CTM2013-48163) of the Spanish Government.

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.

International audience; This paper is an addendum for the availability of the names of 11 new species proposed in Al khatib et al. (2014).

The recent and rapid invasion of Europe and North-America by Drosophila suzukii has generated numerous laboratory and field studies since this fly species is an agricultural pest that causes economical losses by laying eggs and developing in ripening fruits, but also because of its relatedness with the model species Drosophila melanogaster whose biology and genetics are well described. This commentary is based on recent data published by different research groups as well as some of our own preliminary results. It discusses the state of research on D. suzukii and addresses the main following questions : can the wide knowledge on D. melanogaster help us to understand and manage the D. suzukii invasion and how ? Are lab results on D. suzukii really informative on its biology ? How can the ecological impact of an invasive species be evaluated if the ecological niche is poorly described in terms of biodiversity and trophic network ? We also outline constraints for the biological control of this pest species and suggest new possible approaches for its long-term management., L’invasion mondiale de Drosophila suzukii : être une espèce «cousine» d’un organisme-modèle aide-t-il réellement à établir un contrôle biologique ? Espoirs, désillusions et nouvelles perspectives. — L’invasion récente et rapide de Drosophila suzukii en Europe et en Amérique du Nord a suscité de nombreuses études sur le terrain comme en laboratoire. Cette drosophile est en effet à la fois un ravageur important, du fait de son développement dans des fruits à maturité, et une «cousine» de l’espèce modèle Drosophila melanogaster dont la biologie et la génétique sont bien connues. Cet article s’appuie sur les données publiées par différentes équipes et sur des résultats préliminaires pour discuter de l’avancée des recherches et notamment des questions suivantes : en quoi nos connaissances sur D. melanogaster peuvent-elles ou non aider à comprendre et gérer l’invasion de D. suzukii ? Les résultats obtenus en condition de laboratoire avec cette espèce sont-ils représentatifs de sa biologie ? Comment mesurer l’impact écologique d’une espèce invasive si la niche qu’elle vient occuper est peu décrite localement en termes d’espèces présentes et de réseaux trophiques ? Cet article discute aussi des pistes et contraintes en termes de lutte biologique et de biocontrôle., Iacovone A.,Girod P.,Ris Nicolas,Weydert C.,Gibert P.,Poirié M.,Gatti Jean-Luc. Worldwide invasion by Drosophila suzukii : does being the “cousin” of a model organism really help setting up biological control ? Hopes, disenchantments and new perspectives . In: Revue d'Écologie (La Terre et La Vie), supplément n°12, 2015. Les invasions biologiques et leur gestion au carrefour des sciences naturelles et des sciences humaines et sociales. Colloque organisé à Rennes (Université de Rennes 1) du 20 au 22 octobre 2014. pp. 207-214.

National audience; Utilization of microcosms to test invasion biology hypotheses. Understanding the factors underlying establishment and spread of exotic species in order to predict invasion risks is a major goal in invasion biology. Many theoretical studies investigated the ecological and evolutionary components of these factors and their impact on the invasive process. Yet, hypothesis tests through experimental approaches are still scarce because of the practical and ethical difficulties associated with the introduction of exotic species in nature. Thus, most empirical results come from a posteriori analyses of fortuitous invasions, which allow correlative approaches at best and give no information about invasion failures. In this paper, we propose microcosms, i.e. reproducible controlled simplified environments, as an alternative to experimental introductions in natura. From a review of the literature, we discuss the distinctive features of microcosms to test theoretical predictions about invasion. Our analysis focuses on studies involving populations in transitory dynamics after a demographic bottleneck and/or subject to an adaptive challenge, two key characteristics of invasive processes. Despite their small number, these studies have been used successfully to explore the influences of various factors, mainly related to the introduction site characteristics (its abiotic conditions and their spatial and temporal heterogeneity), and to a lesser extent to the introduced individuals themselves (propagule pressure, genetic diversity and adaptations in the introduced population) or the invaded community. We argue that microcosms, as model systems, can be powerful tools to test theoretical hypotheses. They must however be used with care, as they do not account for the same complexity as natural systems. They are thus complementary to theoretical studies and field surveys, and contribute to reinforce the predictive value of invasion biology by linking theory and experimentation.

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.

International audience; Inbreeding and inbreeding depression are key processes in small or isolated populations and are therefore central concerns for the management of threatened or (re) introduced organisms. Haplodiploid species of the order Hymenoptera have a particular status with regard to inbreeding depression. Although recessive deleterious alleles that are expressed in males should be purged, an alternative form of inbreeding depression exists in species with single-locus complementary sex determination (sl-CSD). Under sl-CSD, genetically-related parents have a high probability of producing sterile sons instead of fertile daughters. In this article, we study inbreeding depression in Venturia canescens (Hymenoptera: Ichneumonidae), a parasitoid wasp with sl-CSD. We used a crossing design to manipulate relatedness according to three levels: within-family, between-family and between-population. For each level, several fitness components were measured on parents and female offspring. We found a 20% reduction in egg load at emergence for inbred crosses. Inbred crosses also yielded a higher proportion of males, as expected in a species with sl-CSD. Mating probability, presence of daughters among offspring, body size, symmetry and longevity were unaffected by inbreeding.

International audience

International audience

International audience; Propagule pressure, i.e. the number of individuals introduced, is thought to be a major predictor of the establishment success of introduced populations in the field. Its influence in laboratory experimental systems has however been questioned. In fact, other factors involved in long-term population persistence, like habitat size, were usually found to explain most of the dynamics of experimental populations. To better understand the respective influence of short- and long-term factors and their potential interaction on extinction dynamics in experimental systems, we investigated the influence of propagule pressure, habitat size and genetic background on the early dynamics of laboratory-based populations of a hymenopteran parasitoid. The amount of demographic variance differed between establishment and persistence phase and was influenced by habitat size and genetic background (geographic strain), but independent of propagule pressure. In contrast, the probability of extinction within five generations depended on the genetic background and on the interaction between propagule pressure and habitat size. Vulnerability to extinction in small size habitats was increased when populations were founded with a small number of individuals, but this effect was delayed until the third to fifth generations. These results indicate that demographic stochasticity is influential during population establishment, but is not affected by the genetic variability of propagules. On the other hand, extinction might be influenced by a genetic Allee effect triggered by the combination of low propagule pressure and genetic drift. Finally, we documented consistent differences between genetic backgrounds in both deterministic and stochastic population dynamics patterns, with major consequences on extinction risk and ultimately population establishment.