Another Chapter in the History of the European Invasion by the Western Conifer Seed Bug, Leptoglossus occidentalis: The Iberian Peninsula

The Western conifer seed bug, Leptoglossus occidentalis, is native to North America and has already been considered a significant pest in several European countries since its first observation in Italy in 1999. In Spain and Portugal, it was recorded for the first time in 2003 and 2010, respectively, and its impact on Stone Pine (Pinus pinea) is of major concern. Before developing control measures for this insect pest, it is paramount to clarify its spatiotemporal dynamics of invasion. Therefore, in this study, we aimed to (a) characterise the genetic structure and diversity and (b) invasion pathways of L. occidentalis populations in the Iberian Peninsula. To do so, specimens of L. occidentalis were collected at fourteen sites widely distributed within the Iberian Peninsula. We used mtDNA sequences of Cytochrome b and eleven microsatellite markers to characterise the genetic diversity and the population structure in the Iberian Peninsula. Our genetic results combined with the observational dates strongly support a stratified expansion of L. occidentalis invasion in the Iberian Peninsula proceeding from multiple introductions, including at least one in Barcelona, one in Valencia, and one in the west coast or in the Southeastern region.Ana Farinha received support from Fundação para a Ciência e a Tecnologia I.P. (FCT-MCES) through a PhD scholarship (PD/BD/52403/2013). Manuela Branco is supported by the Forest Research Centre (CEF) (UIDB/00239/2020) and the Laboratory for Sustainable Land Use and Ecosystem Services—TERRA (LA/P/0092/2020) funded by FCT, Portugal. European Project H2020 “Adaptive breeding for productive, sustainable and resilient forests under climate change” (B4EST; grant agreement No. 773383). Cost action FP1203: European Non-Wood Forest Products Network (NWFPs), European Cooperation in Science and Technology (COST)

Etudes entreprises sur Cryptococcus fagi Baersp. en Haute-Normandie

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Study of the mechanism of resistance to Bacillus thuringiensis Cry3A toxin in a natural population of the leaf beetle, Chrysomela tremulae (Coleoptera: Chrysomelidae)

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Genetics of resistance to transgenic Bacillus thuringiensis poplars in the poplar leaf beetle, Chrysomela tremulae F. (Coleoptera: Chrysomelidae)

International audienceThe area under genetically engineered plants producing Bacillus thuringiensis (Bt) toxins is steadily increasing. This increase has magnified the risk of alleles conferring resistance to these toxins being selected in natural populations of target insect pests. The speed at which this selection is likely to occur depends on the genetic characteristics of Bt resistance. We selected a strain of the beetle Chrysomela tremulae Fabricius on a transgenic Bt poplar clone Populus tremula L. x Populus tremuloides Michx producing high levels of B.thuringiensis Cry3Aa toxin. This strain was derived from an isofemale line that generated some F-2 offspring that actively fed on this Bt poplar clone. The resistance ratio of the strain was >6,400. Susceptibility had decreased to such an extent that the mortality of beetles of the strain fed Bt poplar leaves was similar to that of beetles fed nontransgenic poplar leaves. Genetic crosses between susceptible, resistant, and F1 hybrids showed that resistance to the Cry3Aa toxin was almost completely recessive (D-LC = 0.07) and conferred by a single autosomal gene. The concentration of Cry3Aa produced in the transgenic Bt poplar used in this study was 6.34 times higher than the LC99 of the F1 hybrids, accounting for the complete recessivity (D-ML = 0) of survival on Bt poplar leaves. Overall, the genetic characteristics of the resistance of C. tremulae to the Cry3Aa toxin are consistent with the assumptions underlying the high-dose refuge strategy, which aims to decrease the selection of Bt resistance alleles in natural target pest populations

Quand les marqueurs génétiques contredisent les hypothèses historiques : l'origine chypriote inattendue du chalcidien des graines invasif Megastigmus schimitscheki

National audienceData and results presented in the present paper come from the original article: Auger-Rozenberg M.-A., Boivin T., Magnoux E., Courtin C., Roques A., Kerdelhué C., 2012. Inferences on population history of a seed chalcid wasp: invasion success despite a severe founder effect from an unexpected source population. Molecular Ecology, 21 (24), 6086-6103. Most invasive species established in Europe originate from either Asia or North America, but little is currently known about the potential of the Anatolian Peninsula (Asia Minor) and/or the Near East to constitute invasion sources. Mediterranean forests are generally fragile ecosystems that can be threatened by invasive organisms coming from different regions of the Mediterranean Basin, but for which historical data are difficult to gather and the phylogeographic patterns are still poorly understood for most terrestrial organisms. In this study, we characterized the genetic structure of Megastigmus schimitscheki, an invasive seed-feeding insect species originating from the Near East, and elucidated its invasion route in South-eastern France in the mid uggested that the invasive populations originated from Turkey. To disentangle the evolutionary history of this introduction, we gathered samples from the main native regions (Taurus Mountains in Turkey, Lebanon and Cyprus) and from the invaded range, that we genotyped using five microsatellite markers and for which we sequenced the mitochondrial Cytochrome Oxidase I gene. We proposed a detailed phylogeographic pattern for the Near East populations, and we unambiguously showed that the French invasive populations originated from Cyprus, thereby contradicting the historical data. Interestingly, we could show that the introduced populations were founded from an extremely restricted number of individuals.A l’heure actuelle, la majorité des espèces d’insectes invasifs présents en Europe, proviennent soit d’Asie soit d’Amérique du Nord. On connait peu de choses sur les risques d’invasion en provenance d’Asie Mineure et du Proche-Orient. Les écosystèmes forestiers méditerranéens peuvent être la cible d’invasions originaires de tout le Bassin Méditerranéen mais peu de données historiques sont accessibles, et il n’existe pas beaucoup d’études phylogéographiques sur les organismes terrestres présents dans ces régions. Dans notre étude, nous avons analysé la structure génétique du chalcidien des graines de cèdres, Megastigmus schimitscheki, dans sa zone d’origine (Turquie, Liban et Chypre) et dans le sud-est de la France où il a été accidentellement introduit dans les années 90, et nous avons cherché à inférer les routes d’invasions. Pour cela, nous avons séquençé un fragment d’ADN mitochondrial et génotypé des populations des différentes zones à l’aide de cinq marqueurs microsatellites. Comme la plupart des cèdres plantés en France sont issus de graines importées de Turquie, l’hypothèse la plus plausible était que ce ravageur ait été importé en France avec des lots de graines turques. Les résultats obtenus nous ont permis de déterminer la structuration de l’insecte dans son aire native et de montrer sans ambigüité que les populations envahissantes proviennent de Chypre, ce qui contredit les données historiques. Cette invasion a de plus eu lieu à partir d’un nombre très réduit d’insectes fondateurs

Incongruent evolutionary histories of two parasitoids in the Mediterranean Basin: influence of host specialization and ecological characteristics

International audienceAim The pine processionary moth (PPM) is a species complex containing two congeneric taxa, namely Thaumetopoea pityocampa and Thaumetopoea wilkinsoni, with a circum-Mediterranean distribution and a strong geographical structure. We developed comparative phylogeographies for two of the main natural enemies of the PPM, the egg parasitoids Baryscapus servadeii and Ooencyrtus pityocampae, to determine to what extent their Quaternary histories were parallel and mirrored that of their host. Location Pine and cedar forests around the Mediterranean Basin. Methods Egg masses of the PPM were sampled from its whole range and parasitoids allowed to emerge in the laboratory. We sequenced one mitochondrial fragment from 303 individuals of B. servadeii and 239 of O. pityocampae, and the nuclear ITS2 for a subset of the samples. The distribution of genetic diversity, network of alleles and AMOVAs were analysed to decipher the phylogeographical structures, and PPM and host plant effects. Results Results differed drastically between the two parasitoid species. We found 87 haplotypes and five ITS alleles for B. servadeii, which showed a strong phylogeographical structure over its distribution range. We identified four divergent clades, one of them further forming four haplogroups. Refugial areas were similar to those of the host. AMOVA showed that over 40% of the variance could be explained by the insect host structure. In contrast, O. pityocampae showed 16 closely related haplotypes, one corresponding to 60% of the individuals. PPM structure explained only 15% of the variance. The effects of the pine host were limited in both parasitoid species. Main conclusions Baryscapus servadeii probably survived Quaternary climatic oscillations in long-term refugia where the PPM host was also continuously present. Although not strictly parallel, its history showed high degrees of similarity with that of the host. Conversely, results suggest that O. pityocampae had different climatic requirements and experienced severe bottleneck(s) during the Quaternary. Yet, it efficiently recolonized its main host range, probably helped by its parthenogenetic reproduction and possibly also by local host shifts

Contrasted genetic patterns in two egg-parasitoids associated with the complex species of the processionary moth Thaumetopoea pityocampa/wilkinsoni around the Mediterranean basin

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Inferences on population history of a seed chalcid wasp: invasion success despite a severe founder effect from an unexpected source population.

International audienceMost invasive species established in Europe originate from either Asia or North America, but little is currently known about the potential of the Anatolian Peninsula (Asia Minor) and/or the Near East to constitute invasion sources. Mediterranean forests are generally fragile ecosystems that can be threatened by invasive organisms coming from different regions of the Mediterranean Basin, but for which historical data are difficult to gather and the phylogeographic patterns are still poorly understood for most terrestrial organisms. In this study, we characterized the genetic structure of Megastigmus schimitscheki, an invasive seed-feeding insect species originating from the Near East, and elucidated its invasion route in South-eastern France in the mid 1990s. To disentangle the evolutionary history of this introduction, we gathered samples from the main native regions (Taurus Mountains in Turkey, Lebanon and Cyprus) and from the invaded region that we genotyped using five microsatellite markers and for which we sequenced the mitochondrial Cytochrome Oxidase I gene. We applied a set of population genetic statistics and methods, including approximate Bayesian computation. We proposed a detailed phylogeographic pattern for the Near East populations, and we unambiguously showed that the French invasive populations originated from Cyprus, although the available historical data strongly suggested that Turkey could be the most plausible source area. Interestingly, we could show that the introduced populations were founded from an extremely restricted number of individuals that realized a host switch from Cedrus brevifolia to C. atlantica. Evolutionary hypotheses are discussed to account for this unlikely scenario

When genetic markers contradict historical hypotheses: an unexpected Cypriot origin for the invasive seed chalcid Megastigmus schimitscheki.

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Traçage des routes d’invasion d’un insecte ravageur polyphage : le cas du capricorne asiatique Anoplophora glabripennis

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