Projet ADRIEN - Arbres Dispersés et Rôle dans les Invasions d'Espèces Nuisibles

En lien avec le flyer : http://prodinra.inra.fr/record/370006Le programme ADRIEN avait pour objectif de mieux comprendre le rôle des arbres hors forêts dans la distribution des bio-agresseurs invasifs des milieux forestiers. L'échelle d'étude était la région Centre qui dispose de différents types de paysage. Le programme d'étude a permis de mieux comprendre comment les différentes essences d'arbres se répartissent sur le territoire en fonction du contexte paysager, et a montré comment la répartition des différents sujets sur le territoire influençait la dispersion des bioagresseurs. Les 3 organismes modèles retenues pour l'étude étaient : la chenille processionnaire du pin, la rouille foliaire à Melampsora larici-populina des peupliers et mélèzes et le puceron lanigère du peuplier. Le projet s'est articulé autour de 2 types de tâches : "Inventaire des arbres hôtes" et "Distribution et flux des espèces associées". Les principales conclusions de ce projet sont : Une forte contribution du patrimoine arboré privé dans les continuités écologiques en ville (et à l'interface milieu urbain / milieu rural). Une très faible variabilité génétique des peupliers d’ornement dans nos paysages ruraux et urbains, avec la prédominance du peuplier d’Italie et de ses descendants. Un rôle majeur des arbres ornementaux dans la forte perméabilité de la Beauce à la dispersion de la processionnaire du pin. Les populations de puceron lanigère du peuplier en Centre-Val de Loire sont issues de l’émergence récente de populations locales, et non de la dispersion d’une population méridionale. Le milieu urbain met bien en présence les deux hôtes de la rouille du peuplier à Melampsora larici-populina en dehors de leur aire commune naturelle et le champignon est en mesure d’y boucler son cycle biologique

Chemical and genetic evidences that multiple hornet colonies attack honeybee colonies

International audienceThe yellow-legged hornet, Vespa velutina nigrithorax, is an invasive species that is causing numerous ecological and economic problems, particularly for beekeepers, whose apiaries are seriously affected by hornet predation. The effects may be intensified if hornet workers from different colonies are preying upon bees from the same apiary. Therefore, to determine whether such could occur, we sampled hornets found within identifiable colonies versus in front of bee hives. We employed two complementary methodological approaches: the analysis of chemical markers (i.e., cuticular hydrocarbons) and genetic markers (i.e., microsatellites). Although there was chemical variation among hornets, we determined that at least two chemically homogeneous hornet groups could be found within each apiary studied (using Kmeans clustering). Furthermore, when hornet chemical dissimilarity was quantified at three different levels (within apiaries, within hornet colonies, and between hornet colonies), we discovered that the within-apiary dissimilarity was intermediate relative to within-colony and between-colony dissimilarity, suggesting that the hornets within a given apiary represented a mixture of individuals from more than one colony. Based on the genetic markers, hornet genetic diversity was low at the population level, as expected for this introduced species. That said, the genetic results mirrored the chemical results: genetic dissimilarity was larger between colonies and smaller within colonies. However, the hornets within a given apiary displayed an intermediate dissimilarity value. Consequently, both our chemical and genetic findings suggested that apiaries could be attacked by hornets from more than one colony

Les pucerons face aux changements globaux

International audienceGlobal warming is one of the principal challenges facing insects worldwide. It affects individual species and interactions between species directly through effects on their physiology and indirectly through effects on their habitat. Aphids are particularly sensitive to temperature changes due to certain specific biological features of this group. Effects on individuals have repercussions for aphid diversity and population dynamics. At a pan-European scale, the EXAMINE observation network has provided evidence for an increase in the number of aphid species present over the last 30 years and for earlier spring flights. We review these results and provide a review of the principal effects of global warming on aphid communities.Le réchauffement climatique compte parmi les principaux changements globaux auxquels les insectes doivent faire face. Il affecte la biologie et l’écologie des espèces, en agissant directement sur la physiologie des organismes, ou indirectement à travers des modifications de leur habitat. De par leurs spécificités biologiques, les pucerons sont particulièrement sensibles à ces changements. Les effets individuels ont, à l’échelle régionale, des répercussions sur la biodiversité des pucerons, le fonctionnement de leurs populations et plus globalement encore sur les interactions entre les pucerons, leurs plantes-hôtes et leurs ennemis naturels. À l’échelle européenne, le réseau d’observation EXAMINE a permis de mettre en évidence au cours des 30 dernières années un enrichissement du nombre des espèces présentes et une précocité de plus en plus grande des populations lors de leurs migrations printanières. L’exposé de ces résultats est complété par une revue bibliographique des principaux effets des changements globaux sur les communautés aphidiennes

Caractérisation du comportement alimentaire du puceron lanigère du peuplier par la technique d’électropénétrographie

International audienc

Caractérisation du comportement alimentaire du puceron lanigère du peuplier par la technique d’électropénétrographie

International audienc

Exceptional plant penetration and feeding upon cortical parenchyma cells by the woolly poplar aphid.

International audienceForty percent of aphids live wholly or partly on trees, most species being associated with leaves or petioles. Species able to exploit woody parts have either specific adaptations, such as extra long stylets that allow them to reach the phloem, or the ability to induce galls. The woolly poplar aphid, Phloeomyzus passerinii (Signoret) (Hemiptera: Aphididae), colonizes the trunks and base of the lower branches of mature poplars and causes cortical necrosis leading to the death of trees where infestation is heavy. Very little is known about the mode of feeding of P. passerinii. This study looked at the feeding behavior of P. passerinii on stem-cuttings of Populus x canadensis Moench using: (i) histological analyses of the feeding site and stylet pathway and (ii) electrical penetration graphs (EPG, DC) based on parthenogenetic apterous females on woody tissues. The histological and EPG results showed that stylets of P. passerinii penetrated into the plant tissues following a straight unbranched extracellular and intracellular pathway to reach the cortical parenchyma. Compared to EPGs for phloem sap feeding aphids, there were differences in the waveforms A and C whereas a new waveform Icp was described. Based on histological analyses and previous descriptions of EPG waveforms, correlations with the stylet tip position and aphid activities within bark tissues are discussed. A pathway and a sustained intracellular phase were distinguished, both occurring in the cortical parenchyma cells. The bark aphid feeding mode is discussed in relation to the damage caused and in terms of changes in the aphid's diet

An American termite in Paris: temporal colony dynamics

International audienceTermites of the genus Reticulitermes are widespread invaders, particularly in urban habitats. Their cryptic and subterranean lifestyle makes them difficult to detect, and we know little about their colony dynamics over time. In this study we examined the persistence of Reticulitermes flavipes (Kollar) colonies in the city of Paris over a period of 15 years. The aim was (1) to define the boundaries of colonies sampled within the same four areas over two sampling periods, (2) to determine whether the colonies identified during the first sampling period persisted to the second sampling period, and (3) to compare the results obtained when colonies were delineated using a standard population genetic approach versus a Bayesian clustering method that combined both spatial and genetic information. Herein, colony delineations were inferred from genetic differences at nine microsatellite loci and one mitochondrial locus. Four of the 18 identified colonies did not show significant differences in their genotype distributions between the two sampling periods. While allelic richness was low, making it hard to reliably distinguish colony family type, most colonies appeared to retain the same breeding structure over time. These large and expansive colonies showed an important ability to fuse (39% were mixed-family colonies), contained hundreds of reproductives and displayed evidence of isolation-by-distance, suggesting budding dispersal. These traits, which favor colony persistence over time, present a challenge for pest control efforts, which apply treatment locally. The other colonies showed significant differences, but we cannot exclude the possibility that their genotype distributions simply changed over time

Wooly poplar aphid - progress made by research

Since 1995, wooly poplar aphids have been responsible for considerable damage to French poplar groves. The damage has spread from the southwest towards the north and the east and has now reached Burgundy and Picardy. The forest entomology team at the University of Orleans has been conducting research since 2008 to elucidate the life history of the insect responsible (a poorly known indigenous species), understand the reasons for the damage and its spread, the very large differences in cultivar susceptibility, determine how cultivar, climate change and level of aggressiveness of the aphid populations affect the spread of damage and its spatial heterogeneity, and finally to offer control methods for the pest. This article provides and overview of current research resultsDepuis 1995, le puceron lanigère du Peuplier est responsable de dégâts considérables dans les peupleraies françaises. Depuis le sud-ouest de notre pays, les dommages se sont étendus vers le nord et l’est et atteignent maintenant la Bourgogne et la Picardie. L’équipe entomologie forestière de l’université d’Orléans développe depuis 2008 des travaux de recherche pour élucider la biologie de l’insecte en cause (une espèce indigène très mal connue), comprendre l’origine des dégâts et les raisons de leur extension, connaître les raisons des variations très importantes de sensibilité des cultivars, définir le rôle de ces dernières, celui des modifications climatiques ainsi que celui des niveaux d’agressivité des populations de puceron dans l’extension des dégâts et leur hétérogénéité spatiale, et tenter de proposer in fine des méthodes de contrôle des populations du ravageur. Le présent article fait le point sur les résultats actuels de ces recherche

Invasion Dynamics of A Termite, Reticulitermes flavipes, at Different Spatial Scales in France

Termites are social insects that can also be major pests. A well-known problem species is the subterranean termite, Reticulitermes flavipes. It is invasive in France and is thought to have arrived from Louisiana during the 18th century. While the putative source of French populations has been identified, little is known about how the termite spread following its establishment. Here, we examined expansion patterns at different spatial scales in urban areas to clarify how R. flavipes spread in France. Based on our analyses of phylogeography and population genetics, results suggest a scenario of successive introductions into the Charente-Maritime region, on the Atlantic Coast. Two major expansion fronts formed: one that spread toward the northeast and the other toward the southeast. At the regional scale, different spatial and genetic distribution patterns were observed: there was heterogeneity in Île-de-France and aggregation in Centre-Val de Loire. At the local scale, we found that our three focal urban sites each formed a single large colony that contained several secondary reproductives. Our findings represent a second step in efforts to reconstruct termite’s invasion dynamics. They also highlight the role that may have been played by the French railway network in transporting termites over long distances