L'invasion du capricorne

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L'invasion du capricorne
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Le capricorne asiatique Anoplophora glabripennis est un exemple d’insecte ayant bénéficié du commerce international depuis l’Asie pour envahir une partie de l’Amérique du Nord où il est présent depuis les années 1990, et de l’Europe où sa présence a été détectée au début des années 2000. Cette espèce hautement polyphage se développe dans les arbres urbains et peut causer leur mort, soulignant l’importance du contrôle de sa population. En utilisant une approche pluridisciplinaire sur la base du modèle A. glabripennis, cette thèse vise à apporter de nouveaux éléments pour la compréhension globale des invasions biologiques. Dans un premier temps, j’ai cherché à retracer son cheminement dans le monde. Dans un second temps, j’ai cherché à savoir si certaines de ses caractéristiques biologiques avaient contribué au succès de son invasion. Enfin, j’ai abordé la question de l’impact écologique d’A.glabripennis en me focalisant sur les modifications de la faune de xylophages que sa présence aurait pu entrainer.Les résultats obtenus au cours de cette thèse ont permis de mettre en évidence une invasion complexe incluant plusieurs introductions ainsi qu’un scénario de tête de pont entre l’Amérique du Nord et l’Europe. Il apparait également que certains traits de l’espèce ont contribué à modeler son schéma de distribution. Sa résistance au stress thermique notamment a probablement favorisé son installation sous des climats variés. Par ailleurs, la dispersion naturelle d’A. glabripennis semble très limitée, mais mes résultats indiquent que l’espèce n’est pas restreinte par ses capacités physiologiques pour disperser. Enfin, l’étude préliminaire des faunes envahies ne révèle pas pour le moment d’effet de l’espèce sur les autres Cérambycidés.Au regard des autres cas d’invasion documentés, le cas d’A.glabripennis souligne donc la diversité des caractéristiques des espèces devenant invasives, et confirme la difficulté d’en dresser un portrait type.
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Insect invasions, the establishment and spread of nonnative insects in new regions, can have extensive economic and environmental consequences. Increased global connectivity accelerates rates of introductions, while climate change may decrease the barriers to invader species’ spread. We follow an individual-level insect- and arachnid-centered perspective to assess how the process of invasion is influenced by phenotypic heterogeneity associated with dispersal and stress resistance, and their coupling, across the multiple steps of the invasion process. We also provide an overview and synthesis on the importance of environmental filters during the entire invasion process for the facilitation or inhibition of invasive insect population spread. Finally, we highlight important research gaps and the relevance and applicability of ongoing natural range expansions in the context of climate change to gain essential mechanistic insights into insect invasions. Expected final online publication date for the Annual Review of Entomology Volume 63 is January 7, 2018. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
The establishment of non-native species is commonly described as occurring in three phases: arrival, establishment, and dispersal. Both arrival and dispersal by the Asian longhorned beetle (Anoplophora glabripennis Motschulsky), a xylophagous Cerambycid native to China and the Korean peninsula, has been documented for multiple locations in both North America and Europe, however the transitional phase, establishment, is not well understood for this species due to the need to rapidly remove populations to prevent dispersal and assist eradication, and the evident variation in the behavior of populations. Here we describe the dynamics of an establishment event for the Asian longhorned beetle in a small, isolated population within the regulated quarantine zone near Worcester, Massachusetts, USA. These data were collected during an opportunity afforded by logistical limits on the Cooperative Asian Longhorned Beetle Eradication Program administered by state, federal, and local government partners. Seventy-one infested red maple (Acer rubrum) trees and 456 interspersed un-infested trees were surveyed in an isolated, recently established population within a ~0.29 ha stand in a suburban wetland conservation area in which nearly 90% of the trees were host species, and nearly 80% were Acer rubrum. Tree-ring analyses show that within this establishing population, Asian longhorned beetles initially infested one or two A. rubrum, before moving through the stand to infest additional A. rubrum based not on distance or direction, but on tree size, with infestation biased towards trees with larger trunk diameters. Survey data from the larger landscape suggest this population may have generated long-distance dispersers (~1400 m), and that these dispersal events occurred before the originally infested host trees were fully exploited by the beetle. The distribution and intensity of damage documented in this population suggest dispersal here may have been spatially more rapid and diffuse than in other documented infestations. Dispersal at these larger spatial scales also implies that when beetles move beyond the closed canopy of the stand, the direction of dispersal may be linked to prevailing winds. © 2017, Public Library of Science. All rights reserved. This is an open access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication.
Anoplophora glabripennis, the Asian Longhorned Beetle (ALB), is an invasive species of high economic and ecological relevance given the potential it has to cause tree damage, and sometimes mortality, in the United States. Because this pest is introduced by transport in wood-packing products from Asia, ongoing trade activities pose continuous risk of transport and opportunities for introduction. Therefore, a geographic understanding of the spatial distribution of risk factors associated with ALB invasions is needed. Chief among the multiple risk factors are (a) the potential for infestation based on host tree species presence/absence, and (b) the temperature regime as a determinant of ALB’s growth time to maturity. This study uses an empirical model of ALB’s time to maturity as a function of temperature, along with a model of heat transfer in the wood of the host and spatial data describing host species presence/absence data, to produce a map of risk factors across the conterminous United States to define potential for ALB infestation and relative threat of impact. Results show that the region with greatest risk of ALB infestation is the eastern half of the country, with lower risk across most of the western half due to low abundance of host species, less urban area, and prevalence of cold, high elevations. Risk is high in southeastern states primarily because of temperature, while risk is high in northeastern and northern central states because of high abundance of host species.
Theoretically, species with high population structure are likely to expand their range, because marginal populations are free to adapt to local conditions; however, meta-analyses have found a negative relation between structure and invasiveness. The crab Petrolisthes armatus has a wide native range, which has expanded in the last three decades. We sequenced 1718 bp of mitochondrial DNA from native and recently established populations to determine the population structure of the former and the origin of the latter. There was phylogenetic separation between Atlantic and eastern Pacific populations, and between east and west Atlantic ones. Haplotypes on the coast of Florida and newly established populations in Georgia and South Carolina belong to a different clade from those from Yucatán to Brazil, though a few haplotypes are shared. In the Pacific, populations from Colombia and Ecuador are highly divergent from those from Panamá and the Sea of Cortez. In general, populations were separated hundreds to million years ago with little subsequent gene flow. High genetic diversity in the newly established populations shows that they were founded by many individuals. Range expansion appears to have been limited by low dispersal rather than lack of ability of marginal populations to adapt to extreme conditions.
How ectotherms exploit thermal resources has important implications for their habitat utilization and thermal vulnerability to climate warming. To address this issue, we investigated thermal relations of three sympatric lizard species (Eremias argus, Eremias multiocellata, and Phrynocephalus przewalskii) in the desert steppe of Inner Mongolia, China. We determined the thermoregulatory behavior, body temperature (Tb), operative temperature (Te), selected body temperature (Tsel), and critical thermal maximum (CTmax) of adult lizards. Based on these physiological parameters, we quantified the accuracy and effectiveness of thermoregulation as well as thermal-safety margin for these species. The three species were accurate and effective thermoregulators. The P. przewalskii preferred open habitats, and had a higher Tb than the two Eremias lizards, which preferred shade habitats and shuttled more frequently between the shade and sun. This indicated that the three sympatric lizards have different thermoregulatory behavior and thermal physiology, which might facilitate their coexistence in the desert steppe ecosystem. In addition, the P. przewalskii had higher Tsel and CTmax, and a wider thermal-safety margin than the two Eremias lizards, suggesting that the two Eremias lizards would be more vulnerable to climate warming than P. przewalskii.
Knowing the phylogeographic structure of invasive species is important for understanding the underlying processes of invasion. The micromoth Phyllonorycter issikii, whose larvae damage leaves of lime trees Tilia spp., was only known from East Asia. In the last three decades, it has been recorded in most of Europe, Western Russia and Siberia. We used the mitochondrial cytochrome c oxidase subunit I (COI) gene region to compare the genetic variability of P. issikii populations between these different regions. Additionally, we sequenced two nuclear genes (28S rRNA and Histone 3) and run morphometric analysis of male genitalia to probe for the existence of cryptic species.
The analysis of COI data of 377 insect specimens collected in 16 countries across the Palearctic revealed the presence of two different lineages: P. issikii and a putative new cryptic Phyllonorycter species distributed in the Russian Far East and Japan. In P. issikii, we identified 31 haplotypes among which 23 were detected in the invaded area (Europe) and 10 were found in its putative native range in East Asia (Russian Far East, Japan, South Korea and China), with only two common haplotypes. The high number of haplotypes found in the invaded area suggest a possible scenario of multiple introductions. One haplotype H1 was dominant (119 individuals, 67.2%), not only throughout its expanding range in Europe and Siberia but, intriguingly, also in 96% of individuals originating from Japan. We detected eight unique haplotypes of P. issikii in East Asia. Five of them were exclusively found in the Russian Far East representing 95% of individuals from that area. The putative new cryptic Phyllonorycter species showed differences from P. issikii for the three studied genes. However, both species are morphologically undistinguishable. They occur in sympatry on the same host plants in Japan (Sendai) and the Russian Far East (Primorsky krai) without evidence of admixture.
Interactions between invasive species can be difficult to predict and can result in unanticipated impacts of significance for native fauna. Here we show that introduced European rabbits (Oryctolagus cuniculus) create habitat that enables invasive redback spiders (Latrodectus hasselti Thorell, 1870) to establish and prey upon the nationally endangered, endemic Cromwell chafer beetle (Prodontria lewisii Broun, 1904). We examined the spatial relationship between rabbit holes and redback spider occurrence, recorded all prey caught in redback spider webs over a 4-month period, and tested the role rabbit holes play in providing habitat for redback spiders experimentally, by filling in rabbit holes in areas used by spiders and monitoring subsequent occupation of the areas over four months. Redback spiders predominately resided in old rabbit holes, with the highest densities of spiders coinciding with high densities of rabbit holes. Cromwell chafer beetles were commonly caught in webs. Filling in rabbit holes eliminated the presence of redback spiders at all treated sites and reduced prey capture in those areas. Conservation management to protect Cromwell chafer beetles should focus on eliminating rabbits and their holes from beetle habitat.
Insects have presented human society with some of its greatest development challenges by spreading diseases, consuming crops and damaging infrastructure. Despite the massive human and financial toll of invasive insects, cost estimates of their impacts remain sporadic,
spatially incomplete and of questionable quality. Here we compile a comprehensive database of economic costs of invasive insects. Taking all reported goods and service estimates, invasive insects cost a minimum of US$70.0 billion per year globally, while associated health costs exceed US$6.9 billion per year. Total costs rise as the number of estimate increases, although many of the worst costs have already been estimated (especially those related to human health). A lack of dedicated studies, especially for reproducible goods and service estimates, implies gross underestimation of global costs. Global warming as a consequence of climate change, rising human population densities and intensifying international trade will allow these costly insects to spread into new areas, but substantial savings could be achieved by increasing surveillance, containment and public awareness.
Apparent competition, the negative interaction between species mediated by shared natural enemies, is thought to play an important role in shaping the structure and dynamics of natural communities. However, its importance in driving species invasions, and whether the strength of this indirect interaction varies across the latitudinal range of the invasion, has not been fully explored. We performed replicated field experiments at four sites spanning 900 km along the Atlantic Coast of the United States to assess the presence and strength of apparent competition between sympatric native and invasive lineages of Phragmites australis. Four herbivore guilds were considered: stem-feeders, leaf-miners, leaf-chewers and aphids. We also tested the hypothesis that the strength of this interaction declines with increasing latitude. Within each site, native and invasive plants of P. australis were cross-transplanted between co-occurring native and invasive patches in the same marsh habitat and herbivore damage was evaluated at the end of the growing season. Apparent competition was evident for both lineages and involved all but the leaf-chewer guild. For native plants, total aphids per plant was 296% higher and the incidence of stem-feeding and leaf-mining herbivores was 34% and 221% higher, respectively, when transplanted into invasive than native patches. These data suggest that invasive P. australis has a negative effect on native P. australis via apparent competition. Averaged among herbivore types, the indirect effects of the invasive lineage on the native lineage was 57% higher than the reverse situation, suggesting that apparent competition was asymmetric. We also found that the strength of apparent competition acting against the native lineage was comparable to the benefits to the invasive lineage from enemy release (i.e., proportionately lower mean herbivory of the invasive relative to the native taxa). Finally, we found the first evidence that the strength of apparent competition acting against the native lineage (from stem-feeders only) decreased with increasing latitude. These results suggest that not only could apparent competition be of tantamount importance to enemy release in enhancing the establishment and spread of invasive taxa, but also that these indirect and direct herbivore effects could vary over the invasion range.
Temperature directly affects survival, development and reproduction in insects and thereby it is a key environmental driver for geographic distribution and population dynamics. This study aims at testing the survival of Drosophila melanogaster under constant low temperatures (CLTs) (2, 3, 4, and 5°C) vs. fluctuating thermal regimes (FTRs). In the latter, the cold stress period was interrupted daily by 2 h pulses at 20°C. Since acclimation enhances cold tolerance, we tested whether benefits of acclimation can combine with those of FTRs. Since D. melanogaster overwinters as non-reproductive adults, we tested if actively reproducing adults are more susceptible to cold stress than virgin females that have a much reduced reproductive activity. The results show that short interruptions of cold stress enhanced survival of adult flies.Survival was time- and temperature-dependent. Prior acclimation to low temperature allowed flies to better cope with cold stress under CLTs. On the other hand, acclimated flies did not profit from the benefits of FTRs and even showed lower survival under FTRs, probably because flies deacclimated during the periodic warm intervals. Gravid females were overall less cold tolerant than virgin females, and both survived better under FTRs. Cold survival at pupal stage was much lower than at adult stage, and no clear benefit of FTR was observed in this life stage. Our study highlights critical variables to take into account when designing experiments of prolonged exposure to low temperature in insects.
Wood-feeding insects encounter challenging diets containing low protein quantities, recalcitrant carbohydrate sources, and plant defensive compounds. The Asian longhorned beetle (Anoplophora glabripennis) is a wood-feeding insect that attacks and kills a diversity of hardwood tree species. We compared gene expression of midguts collected from larvae feeding in a preferred tree, sugar maple, to those consuming a nutrient-rich artificial diet, to identify genes putatively involved in host plant utilization. Anoplophora glabripennis larvae exhibited differential expression of ~3600 genes in response to different diets. Genes with predicted capacity for plant and microbial carbohydrate usage, detoxification, nutrient recycling, and immune-related genes relevant for facilitating interactions with microbial symbionts were upregulated in wood-feeding larvae compared to larvae feeding in artificial diet. Upregulation of genes involved in protein degradation and synthesis was also observed, suggesting that proteins incur more rapid turnover in insects consuming wood. Additionally, wood-feeding individuals exhibited elevated expression of several mitochondrial cytochrome C oxidase genes, suggesting increased aerobic respiration compared to diet-fed larvae. These results indicate that A. glabripennis modulates digestive and basal gene expression when larvae are feeding in a nutrient-poor, yet suitable host plant compared to a tractable and nutrient-rich diet that is free of plant defensive compounds.
The number of insect species transported to non-native regions is increasing, and, once established, these invasiv
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