The spotted-wing drosophila, Drosophila suzukii, is one of the most damaging invasive fruit pests in the world. It infests a wide range of wild and crop host plants, impacting natural habitats and causing significant economic losses. Leptopilina japonica, a predominant larval parasitoid of D. suzukii in the native areas of the fly, is now spontaneously expanding into non-native areas of its fly host. This study documents the presence and genetic structure of L. japonica collected from various wild and cultivated fruits across 11 sites in France in 2023. Leptopilina japonica emerged from 15% of fruit samples and was strongly positively associated with D. suzukii, showing parasitism rates of up to 38.5%, notably in Lonicera fruits. Despite this, D. suzukii remained dominant, indicating a limited current biocontrol effect, while native parasitoids were nearly absent from samples. Molecular analyses using COI markers revealed 10 distinct haplotypes of the L. j. japonica subspecies in France that clustered into three groups, suggesting multiple introductions and/or migration routes into France from Asia, North America and neighbouring European countries. The lack of nuclear diversity measured from ITS2 markers suggests that the colonization is recent and that the populations experienced a bottleneck process. Nevertheless, a more extensive sampling combined with the use of additional genetic markers would be needed to better understand the origin and spread of L. japonica and its consequences on the equilibrium of Drosophila communities.

Animal movement and behavior are critical to understanding ecological and evolutionary processes. Recent years have witnessed an increase in methodological and technological innovations in video-tracking solutions for phenotyping animal behavior. Although these advances enable the collection of high-resolution data describing the movement of multiple individuals, analyzing and interpreting them remains challenging due to their complexity, heterogeneity, and noisiness. Here, we introduce MoveR, an R package for importing, filtering, visualizing, and analyzing data from common video-tracking solutions. MoveR includes flexible tools for polishing data, removing tracking artifacts, subsetting and plotting individual paths, and computing different movement and behavior metrics.

In theory, the introduction of individuals infected with an incompatible strain of Wolbachia pipientis into a recipient host population should result in the symbiont invasion and reproductive failures caused by cytoplasmic incompatibility (CI). Modelling studies combining Wolbachia invasion and host population dynamics show that these two processes could interact to cause a transient population decline and, in some conditions, extinction. However, these effects could be sensitive to density dependence, with the Allee effect increasing the probability of extinction, and competition reducing the demographic impact of CI. We tested these predictions with laboratory experiments in the fruit fly Drosophila suzukii and the transinfected Wolbachia strain wTei. Surprisingly, the introduction of wTei into D. suzukii populations at carrying capacity did not result in the expected wTei invasion and transient population decline. In parallel, we found no Allee effect but strong negative density dependence. From these results, we propose that competition interacts in an antagonistic way with Wolbachia-induced cytoplasmic incompatibility on insect population dynamics. If future models and data support this hypothesis, pest management strategies using Wolbachia-induced CI should target populations with negligible competition but a potential Allee effect, for instance at the beginning of the reproductive season.

The obscure mealybug, Pseudococcus viburni, is a serious agricultural pest worldwide. The biological control in commercial fields of P. viburni relies on predators and parasitoids, in particular the generalist coccidophagous ladybird Cryptolaemus montrouzieri and the specific parasitoid Acerophagus flavidulus. However, these two natural enemies can establish an intraguild predation interaction, reducing the efficiency of biological control. Cryptolaemus montrouzieri may negatively impact the population dynamics of A. flavidulus if it feeds indifferently on healthy and parasitized mealybugs. With the aim of improving the biological control of P. viburni, in this work, we studied the feeding behavior of C. montrouzieri in the absence or presence of A. flavidulus larvae of different age within mealybugs, in laboratory conditions. Subsequently, with the data obtained, we mathematically modeled the dynamics of P. viburni to study the impact on P. viburni control of different field implementation schedules for the release of ladybird and parasitoid populations. The ladybird fed on parasitized P. viburni but reduced its consumption when they were infested by parasitoids aged of 4 days or more. Modeling results suggest that these feeding preferences of predators may have a positive impact on pest control, that releasing predators and parasitoids together is in general more effective than releasing them independently, and that releasing highly effective predators alone could be the best choice. Modeling results also provide information on different release schedules.

The introduction of the biological control agent Torymus sinensis Kamijo (Hymenoptera, Chalcidoidea, Torymidae) to control the populations of the chestnut gall wasp Dryocosmus kuriphilus Yasumatsu (Hymenoptera, Cynipidae) is considered one of the successful programs in biological control. The species was involved in interspecific hybridisation in Japan and the specimens imported into Europe were derived from this hybrid lineage, showing signs of introgression. The discovery of mitochondrial haplotypes or possible Enolase haplotypes from T. beneficus or of specimens with shorter ovipositor does not necessarily imply that T. beneficus is present in Europe, only that the European specimens are of hybrid origin. Of the native European Torymus species associated with D. kuriphilus , the molecular and morphometric results indicate Torymus notatus (Walker) as the closest species to T. sinensis . The two are part of the same species-group ( cyaneus group), are nested together in the multivariate ratio analysis and are the closest genetically based on all three nuclear markers: Enolase (1.5% divergence), Wingless (2%) and ITS2 (13%). However, on the mitochondrial marker COI the closest species is Torymus rubi (Schrank) at 9.9% divergence. As such, T. notatus is the most likely candidate for accidental interspecific hybridisation if this is to happen in Europe. We provide an illustrated identification key for the European species of Torymus associated with D. kuriphilus , an important but lacking tool for biological control programs.

Native to China, the chestnut gall wasps Dryocosmus kuriphilus Yasumatsu (Hymenoptera, Cynipidae) has invaded several countries on three continents in about half a century. To reduce the negative impact on the chestnut industry, the hymenopteran parasitoid Torymus sinensis Kamijo (Hymenoptera, Torymidae) was firstly translocated from China to Japan and then from Japan to other countries. From an agronomic point of view, this classical biological control programme is perceived as a great success story even if in Japan it was overshadowed by evidence of hybridisation with the indigenous species Torymus beneficus Yasumatsu & Kamijo. Based on numerous specimens collected in France and Italy but also in Asia, as well as on published data, we detected molecular and phenotypic signatures of a possible hybridisation. Our results evidenced for the first time that the European stock of T. sinensis has some rare molecular signatures of historical hybridisation that took place in Japan (0.66% of the mitochondrial haplotypes). Our morphometric study also shows that European and Japanese T. sinensis are morphologically intermediate between the two species that hybridised. The identity of the early‐ and late‐season strains of T. beneficus is discussed. Torymus beneficus late‐season strain (TbL) is considered to be the same as T. sinensis and only the early‐season strain (TbE) is the true T. beneficus . Torymus beneficus is morphologically very close to T. sinensis , and the interspecific distance of COI , though large, is comparable with the larger intraspecific variability found in other Chalcidoidea species. Though the two could be regarded as subspecies, for the stability of nomenclature it is better to continue treating them as distinct species.

Temperature is a main driver of the ecology and evolution of ectotherms. In particular, the ability to move at sub-lethal low temperatures can be described through three thermal tolerance indices-critical thermal minimum (CTmin), chill coma temperature (CCT), and activity recovery (AR). Although these indices have proven relevant for inter-specific comparisons, little is known about their intraspecific variability as well as possible genetic correlations between them. We thus investigated these two topics (intraspecific variability and genetic correlations between thermal tolerance indices) using the minute wasp, Trichogramma cacoeciae. Strains from T. cacoeciae were sampled across three geographic regions in France-two bioclimatic zones along a sharp altitudinal cline in a Mediterranean context (meso-Mediterranean at low elevations and supra-Mediterranean at higher elevations) and a more northwestern area characterized by continental or mountainous climates. Our results evidenced a significant effect of both the longitude and the severity of the cold during winter months on CCT. Results were however counter-intuitive since the strains from the two bioclimatic zones characterized by more severe winters (northwestern area and supra-Mediterranean) exhibited opposite patterns. In addition, a strong positive correlation was observed between CCT and CTmin. Neither strain differentiation nor the covariations between traits seem to be linked with the molecular diversity observed on the part of the mitochondrial marker COI.

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.

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.