Ecological effects of invasive alien insects

Switched after Birth: Performance of the Viburnum Leaf Beetle [Pyrrhalta viburni (Paykull)] after Transfer to a Suboptimal Host Plant

Host plant switching is common among phytophagous insects. Once optimal food sources have been depleted, immature insects may resort to use of suboptimal hosts in order to complete their development. Such host switching may have dramatic consequences for insect fitness. Here we investigate the effects of host switching in larvae of the viburnum leaf beetle, Pyrrhalta viburni, an invasive landscape pest in North America. Specifically, we examine how transfer of 3rd instar larvae from the optimal host Viburnum dentatum to three suboptimal hosts (V. lentago, V. carlesii, and V sieboldii) affects larval development and survivorship to the adult stage. Larval survivorship, pupal weight, and adult weight were overall lower for P. viburni larvae that switched hosts, independently of the suboptimal host tested. This decrease in performance corresponds to a decreased feeding rate on suboptimal hosts. Subsequent choice tests showed that 3rd instar larvae become less choosy as they approach pupation, and discriminate less between optimal and suboptimal hosts past a certain weight threshold. In conclusion, P. viburni larvae are able to complete their development on suboptimal hosts, but host switching negatively impacts several fitness correlates. Mixed ornamental gardens containing both optimal and suboptimal Viburnum species may provide to outbreaking P. viburni populations opportunities to survive the depletion of their preferred food sources.

Modelling the impacts of an invasive species across landscapes: a step-wise approach

We estimate the extent of ecological impacts of the invasive Asian paper wasp across different landscapes in New Zealand. We used: (i) a baseline distribution layer (modelled via MaxEnt); (ii) Asian paper wasp nest density (from >460 field plots, related to their preferences for specific land cover categories); and (iii) and their foraging intensity (rates of foraging success, and the time available to forage on a seasonal basis). Using geographic information systems this information is combined and modelled across different landscapes in New Zealand in a step-wise selection process. The highest densities of Asian paper wasps were in herbaceous saline vegetation, followed closely by built-up areas, and then scrub and shrubland. Nest densities of 34 per ha, and occupancy rates of 0.27 were recorded for herbaceous saline vegetation habitats. However, the extent of impacts of the Asian paper wasp remains relatively restricted because of narrow climate tolerances and spatial restriction of preferred habitats. A step-wise process based on geographic information systems and species distribution models, in combination with factors such as distribution, density, and predation, create a useful tool that allows the extent of impacts of invasive species to be assessed across large spatial scales. These models will be useful for conservation managers as they provide easy visual interpretation of results, and can help prioritise where direct conservation action or control of the invader are required.

A unified classification of alien species based on the magnitude of their environmental impacts

We present a method for categorising and comparing alien or invasive species in terms of how damaging they are to the environment, that can be applied across all taxa, scales, and impact metrics.

Species moved by human activities beyond the limits of their native geographic ranges into areas in which they do not naturally occur (termed aliens) can cause a broad range of significant changes to recipient ecosystems; however, their impacts vary greatly across species and the ecosystems into which they are introduced. There is therefore a critical need for a standardised method to evaluate, compare, and eventually predict the magnitudes of these different impacts. Here, we propose a straightforward system for classifying alien species according to the magnitude of their environmental impacts, based on the mechanisms of impact used to code species in the International Union for Conservation of Nature (IUCN) Global Invasive Species Database, which are presented here for the first time. The classification system uses five semi-quantitative scenarios describing impacts under each mechanism to assign species to different levels of impact—ranging from Minimal to Massive—with assignment corresponding to the highest level of deleterious impact associated with any of the mechanisms. The scheme also includes categories for species that are Not Evaluated, have No Alien Population, or are Data Deficient, and a method for assigning uncertainty to all the classifications. We show how this classification system is applicable at different levels of ecological complexity and different spatial and temporal scales, and embraces existing impact metrics. In fact, the scheme is analogous to the already widely adopted and accepted Red List approach to categorising extinction risk, and so could conceivably be readily integrated with existing practices and policies in many regions.

Genetic diversity of a successful colonizer: isolated populations of Metrioptera roeselii regain variation at an unusually rapid rate

Newly founded isolated populations need to overcome detrimental effects of low genetic diversity. The establishment success of a population may therefore depend on various mechanisms such as assortative mating, purging of deleterious alleles, creation of new mutations and/or repeated inflow of new genotypes to reduce the effects of inbreeding and further loss of genetic variation. We compared the level of genetic variation in introduced populations of an insect species (Metrioptera roeselii) far beyond its natural distribution with levels found in their respective founder populations and coupled the data with timing since establishment. This allowed us to analyze if the introduced populations showed signs of temporal changes in genetic variation and have made it possible to evaluate underlying mechanisms. For this, we used neutral genetic markers, seven microsatellite loci and a 676–bp-long sequence of the mtDNA COI gene. All tested indices (allelic richness, unbiased expected heterozygosity, effective size, haplotype diversity, and nucleotide diversity) except inbreeding coefficient had significantly higher values in populations within the founding populations inside the continuous area of the species distribution compared with the introduced populations. A logarithmic model showed a significant correlation of both allelic richness and unbiased expected heterozygosity with age of the isolated populations. Considering the species' inferred colonization history and likely introduction pathways, we suggest that multiple introductions are the main mechanism behind the temporal pattern observed. However, we argue that influences of assortative mating, directional selection, and effects of an exceptional high intrapopulation mutation rate may have impacts. The ability to regain genetic diversity at this level may be one of the main reasons why M. roeselii successfully continue to colonize northern Europe.

Screening of Repellents against Vespid Wasps

Vespid wasps are ecologically beneficial, but they can be a nuisance and dangerous to people due to their tendency to sting. Here, the aim was to screen samples of volatiles (i.e., essential oils and pure chemicals) for their repellency against wasps. The number of wasps (mainly Vespula vulgaris) present in a glass box with attractant and 5 µL sample was compared to the number of wasps in a similar box with attractant only. Both boxes were connected to a large glass container harboring 18–35 wasps. Among 66 tested samples, some essential oils from Lamiaceae and Asteraceae, as well as some pure natural compounds such as the monoterpenes (−)-terpinen-4-ol and isopulegol showed a significant repellency against vespids. Our results corroborate the potential of (mixtures of) volatiles in repelling these insects.

Environmental risk assessment for plant pests: a procedure to evaluate their impacts on ecosystem services

The current methods to assess the environmental impacts of plant pests differ in their approaches and there is a lack of the standardized procedures necessary to provide accurate and consistent results, demonstrating the complexity of developing a commonly accepted scheme for this purpose. By including both the structural and functional components of the environment threatened by invasive alien species (IAS), in particular plant pests, we propose an environmental risk assessment scheme that addresses this complexity. Structural components are investigated by evaluating the impacts of the plant pest on genetic, species and landscape diversity. Functional components are evaluated by estimating how plant pests modify ecosystem services in order to determine the extent to which an IAS changes the functional traits that influence ecosystem services. A scenario study at a defined spatial and temporal resolution is then used to explore how an IAS, as an exogenous driving force, may trigger modifications in the target environment. The method presented here provides a standardized approach to generate comparable and reproducible results for environmental risk assessment as a component of Pest Risk Analysis. The method enables the assessment of overall environmental risk which integrates the impacts on different components of the environment and their probabilities of occurrence. The application of the proposed scheme is illustrated by evaluating the environmental impacts of the invasive citrus long-horn beetle, Anoplophora chinensis.

Consequences of asymmetric competition between resident and invasive defoliators: a novel empirically based modelling approach

Invasive species can have profound effects on a resident community via indirect interactions among community members. While long periodic cycles in population dynamics can make the experimental observation of the indirect effects difficult, modelling the possible effects on an evolutionary time scale may provide the much needed information on the potential threats of the invasive species on the ecosystem. Using empirical data from a recent invasion in northernmost Fennoscandia, we applied adaptive dynamics theory and modelled the long term consequences of the invasion by the winter moth into the resident community. Specifically, we investigated the outcome of the observed short-term asymmetric preferences of generalist predators and specialist parasitoids on the long term population dynamics of the invasive winter moth and resident autumnal moth sharing these natural enemies. Our results indicate that coexistence after the invasion is possible. However, the outcome of the indirect interaction on the population dynamics of the moth species was variable and the dynamics might not be persistent on an evolutionary time scale. In addition, the indirect interactions between the two moth species via shared natural enemies were able to cause asynchrony in the population cycles corresponding to field observations from previous sympatric outbreak areas. Therefore, the invasion may cause drastic changes in the resident community, for example by prolonging outbreak periods of birch-feeding moths, increasing the average population densities of the moths or, alternatively, leading to extinction of the resident moth species or to equilibrium densities of the two, formerly cyclic, herbivores.

Behavioral assays for studies of host plant choice and adaptation in herbivorous insects

The association of insect herbivores with their host plants is influenced by behaviors governing acceptance of those plants for feeding and oviposition. Behavioral changes accompany and may even precede host range expansion. Characterization and quantification of specific behaviors often form the basis of studies on host plant adaptation and chemical ecology. Behavioral assays of insects are usually designed to measure attraction for feeding or oviposition in relation to their host plants or specific chemistry. We review behavioral assays of insect herbivores with host plants or the volatiles they emit, with special consideration given to design, analysis, and interpretation to maximize ecological relevance. A toolkit of robust assays can help address fundamental issues at the intersection of ecology and evolution, such as the underpinnings of plant-insect interactions and the identification of genes involved in host race formation.

Large shift in symbiont assemblage in the invasive red turpentine beetle

Changes in symbiont assemblages can affect the success and impact of invasive species, and may provide knowledge regarding the invasion histories of their vectors. Bark beetle symbioses are ideal systems to study changes in symbiont assemblages resulting from invasions. The red turpentine beetle (Dendroctonus valens) is a bark beetle species that recently invaded China from its native range in North America. It is associated with ophiostomatalean fungi in both locations, although the fungi have previously been well-surveyed only in China. We surveyed the ophiostomatalean fungi associated with D. valens in eastern and western North America, and identified the fungal species using multi-gene phylogenies. From the 307 collected isolates (147 in eastern North America and 160 in western North America), we identified 20 species: 11 in eastern North America and 13 in western North America. Four species were shared between eastern North America and western North America, one species (Ophiostoma floccosum) was shared between western North America and China, and three species (Grosmannia koreana, Leptographium procerum, and Ophiostoma abietinum) were shared between eastern North America and China. Ophiostoma floccosum and O. abietinum have worldwide distributions, and were rarely isolated from D. valens. However, G. koreana and L. procerum are primarily limited to Asia and North America respectively. Leptographium procerum, which is thought to be native to North America, represented >45% of the symbionts of D. valens in eastern North America and China, suggesting D. valens may have been introduced to China from eastern North America. These results are surprising, as previous population genetics studies on D. valens based on the cytochrome oxidase I gene have suggested that the insect was introduced into China from western North America.

Release of genetically engineered insects: a framework to identify potential ecological effects

Genetically engineered (GE) insects have the potential to radically change pest management worldwide. With recent approvals of GE insect releases, there is a need for a synthesized framework to evaluate their potential ecological and evolutionary effects. The effects may occur in two phases: a transitory phase when the focal population changes in density, and a steady state phase when it reaches a new, constant density. We review potential effects of a rapid change in insect density related to population outbreaks, biological control, invasive species, and other GE organisms to identify a comprehensive list of potential ecological and evolutionary effects of GE insect releases. We apply this framework to the Anopheles gambiae mosquito - a malaria vector being engineered to suppress the wild mosquito population - to identify effects that may occur during the transitory and steady state phases after release. Our methodology reveals many potential effects in each phase, perhaps most notably those dealing with immunity in the transitory phase, and with pathogen and vector evolution in the steady state phase. Importantly, this framework identifies knowledge gaps in mosquito ecology. Identifying effects in the transitory and steady state phases allows more rigorous identification of the potential ecological effects of GE insect release.

Environmental consequences of invasive species: greenhouse gas emissions of insecticide use and the role of biological control in reducing emissions

Greenhouse gas emissions associated with pesticide applications against invasive species constitute an environmental cost of species invasions that has remained largely unrecognized. Here we calculate greenhouse gas emissions associated with the invasion of an agricultural pest from Asia to North America. The soybean aphid, Aphis glycines, was first discovered in North America in 2000, and has led to a substantial increase in insecticide use in soybeans. We estimate that the manufacture, transport, and application of insecticides against soybean aphid results in approximately 10.6 kg of carbon dioxide (CO2) equivalent greenhouse gasses being emitted per hectare of soybeans treated. Given the acreage sprayed, this has led to annual emissions of between 6 and 40 million kg of CO2 equivalent greenhouse gasses in the United States since the invasion of soybean aphid, depending on pest population size. Emissions would be higher were it not for the development of a threshold aphid density below which farmers are advised not to spray. Without a threshold, farmers tend to spray preemptively and the threshold allows farmers to take advantage of naturally occurring biological control of the soybean aphid, which can be substantial. We find that adoption of the soybean aphid economic threshold can lead to emission reductions of approximately 300 million kg of CO2 equivalent greenhouse gases per year in the United States. Previous studies have documented that biological control agents such as lady beetles are capable of suppressing aphid densities below this threshold in over half of the soybean acreage in the U.S. Given the acreages involved this suggests that biological control results in annual emission reductions of over 200 million kg of CO2 equivalents. These analyses show how interactions between invasive species and organisms that suppress them can interact to affect greenhouse gas emissions.

Molecular genetics and genomics generate new insights into invertebrate pest invasions

Invertebrate pest invasions and outbreaks are associated with high social, economic, and ecological costs, and their significance will intensify with an increasing pressure on agricultural productivity as a result of human population growth and climate change. New molecular genetic and genomic techniques are available and accessible, but have been grossly underutilized in studies of invertebrate pest invasions, despite that they are useful tools for applied pest management and for understanding fundamental features of pest invasions including pest population demographics and adaptation of pests to novel and/or changing environments. Here, we review current applications of molecular genetics and genomics in the study of invertebrate pest invasions and outbreaks, and we highlight shortcomings from the current body of research. We then discuss recent conceptual and methodological advances in the areas of molecular genetics/genomics and data analysis, and we highlight how these advances will further our understanding of the demographic, ecological, and evolutionary features of invertebrate pest invasions. We are now well equipped to use molecular data to understand invertebrate dispersal and adaptation, and this knowledge has valuable applications in agriculture at a time when these are critically required.

The invasive spider mite Tetranychus evansi (Acari: Tetranychidae) alters community composition and host-plant use of native relatives

The tomato spider mite Tetranychus evansi Baker and Pritchard (Acari: Tetranychidae), is a worldwide pest of solanaceous crops that has recently invaded many parts of the world. In the present study we examined the ecological impact of its arrival in the Mediterranean region. The spider mite and phytoseiid mite assemblages in various crop and non-crop plants in three areas of Valencia (Spain) were studied a few months before and 10 years after the invasion of T. evansi. According to rarefaction analyses, the invasion of T. evansi did not affect neither the total number of species in the mite community examined (spider mite and phytoseiid species) nor the number of species when the two communities were examined separately. However, after the invasion, the absolute and relative abundance of the native Tetranychus species was significantly reduced. Before the invasion, T. urticae and T. turkestani were the most abundant spider mites, accounting for 62.9 and 22.8 % of the specimens. After the invasion, T. evansi became the most abundant species, representing 60 % of the total spider mites recorded, whereas the abundance of T. urticae was significantly reduced (23 %). This reduction took place principally on non-crop plants, where native species were replaced by the invader. Null model analyses provided evidence for competition structuring the spider mite community on non-crop plants after the invasion of T. evansi. Resistance to acaricides, the absence of efficient native natural enemies, manipulation of the plant defenses and the web type produced by T. evansi are discussed as possible causes for the competitive displacement.

Use of ecological niche models to predict the distribution of invasive species: a scientometric analysis

We conducted a scientometric analysis to determine the main trends and gaps of studies on the use of ecological niche models (ENMs) to predict the distribution of invasive species. We used the database of the Thomson Institute for Scientific Information (ISI). We found 190 papers published between 1991 and 2010 in 82 journals. The number of papers was low in the 1990s, but began to increase after 2003. One-third of the papers were published by researchers from the United States of America, and consequently, the USA was also the most studied region. The majority of studies were carried out in terrestrial environments, while only a few investigated aquatic systems, probably because important aquatic predictor variables are scarce or unavailable for most regions in the world. Species-occurrence records were mainly composed of presence-only records, and almost 70% of the studies were carried out with plants and insects. Twenty-three different distribution modelling methods were used. The Genetic Algorithm for Rule-set Production (GARP) was used most often. Our scientometric analysis showed a growing interest in the use of ENMs to predict the distribution of invasive species, especially in the last decade, which is probably related to the increase in species introductions worldwide. Among some important gaps that need to be filled, the relatively small number of studies conducted in developing countries and in aquatic environments deserves careful attention.

Widespread occurrence of chemical residues in beehive matrices from apiaries located in different landscapes of Western France

BACKGROUND

The honey bee, Apis mellifera, is frequently used as a sentinel to monitor environmental pollution. In parallel, general weakening and unprecedented colony losses have been reported in Europe and the USA, and many factors are suspected to play a central role in these problems, including infection by pathogens, nutritional stress and pesticide poisoning. Honey bee, honey and pollen samples collected from eighteen apiaries of western France from four different landscape contexts during four different periods in 2008 and in 2009 were analyzed to evaluate the presence of pesticides and veterinary drug residues.

METHODOLOGY/FINDINGS

A multi-residue analysis of 80 compounds was performed using a modified QuEChERS method, followed by GC-ToF and LC-MS/MS. The analysis revealed that 95.7%, 72.3% and 58.6% of the honey, honey bee and pollen samples, respectively, were contaminated by at least one compound. The frequency of detection was higher in the honey samples (n = 28) than in the pollen (n = 23) or honey bee (n = 20) samples, but the highest concentrations were found in pollen. Although most compounds were rarely found, some of the contaminants reached high concentrations that might lead to adverse effects on bee health. The three most frequent residues were the widely used fungicide carbendazim and two acaricides, amitraz and coumaphos, that are used by beekeepers to control Varroa destructor. Apiaries in rural-cultivated landscapes were more contaminated than those in other landscape contexts, but the differences were not significant. The contamination of the different matrices was shown to be higher in early spring than in all other periods.

CONCLUSIONS/SIGNIFICANCE

Honey bees, honeys and pollens are appropriate sentinels for monitoring pesticide and veterinary drug environmental pollution. This study revealed the widespread occurrence of multiple residues in beehive matrices and suggests a potential issue with the effects of these residues alone or in combination on honey bee health.

Propagule pressure and climate contribute to the displacement of Linepithema humile by Pachycondyla chinensis

Identifying mechanisms governing the establishment and spread of invasive species is a fundamental challenge in invasion biology. Because species invasions are frequently observed only after the species presents an environmental threat, research identifying the contributing agents to dispersal and subsequent spread are confined to retrograde observations. Here, we use a combination of seasonal surveys and experimental approaches to test the relative importance of behavioral and abiotic factors in determining the local co-occurrence of two invasive ant species, the established Argentine ant (Linepithema humile Mayr) and the newly invasive Asian needle ant (Pachycondyla chinensis Emery). We show that the broader climatic envelope of P. chinensis enables it to establish earlier in the year than L. humile. We also demonstrate that increased P. chinensis propagule pressure during periods of L. humile scarcity contributes to successful P. chinensis early season establishment. Furthermore, we show that, although L. humile is the numerically superior and behaviorally dominant species at baits, P. chinensis is currently displacing L. humile across the invaded landscape. By identifying the features promoting the displacement of one invasive ant by another we can better understand both early determinants in the invasion process and factors limiting colony expansion and survival.

Morphological and color differences between island and mainland populations in the Mexican red rump tarantula, Brachypelma vagans

The introduction of species into new ecosystems, especially in small and isolated regions such as islands, offers an excellent opportunity to answer questions of the evolutionary processes occurring in natural conditions on a scale that could never be achieved in laboratory conditions. In this study, we examined the Mexican red rump tarantula Brachypelma vagans Ausserer (Mygalomorphae: Theraphosidae), a species that was introduced to Cozumel Island, Mexico, 40 years ago. This introduction provides an exceptional model to study effects such as morphological variation between island populations and those on the mainland in open habitats facing the island. Intraspecific variation related to the color polymorphism was compared. The aim of this study was to determine the phenotypic differences between continental populations of B. vagans and the introduced population on Cozumel Island. Phenotypic difference was evaluated using two approaches: 1) comparison of the morphometric measurements of adult and juvenile individuals at the local scale and between continental and island populations, and 2) comparison of individual color polymorphism between mainland and island populations. Two locations were sampled within the continental part of the Yucatan peninsula and two on the island of Cozumel. The number of samples analyzed at each site was 30 individuals. The morphometric results showed significant differences between continental and island populations, with bigger individuals on the island. In addition, three new variations of the typical color pattern of B. vagans recorded so far were observed. This study opens the door to further investigations to elucidate the origin of the phenotypic variation of the isolated individuals on Cozumel Island. Also, the widest range of color morphs found for a tarantula species is reported.

Canopy and knowledge gaps when invasive alien insects remove foundation species

The armored scale Aulacaspis yasumatsui invaded the northern range of the cycad Cycas micronesica in 2003, and epidemic tree mortality ensued due to a lack of natural enemies of the insect. We quantified cycad demographic responses to the invasion, but the ecological responses to the selective removal of this foundation species have not been addressed. We use this case to highlight information gaps in our understanding of how alien invasive phytophagous insects force cascading adverse ecosystem changes. The mechanistic role of unique canopy gaps, oceanic island examples and threatened foundation species with distinctive traits are three issues that deserve research efforts in a quest to understand this facet of ecosystem change occurring across multiple settings globally.

Alien insects in Italy: comparing patterns from the regional to European level

The introduction of species outside their native range contributes to the loss of biodiversity, alters the structure and functioning of ecosystems, and damages economy and human health. Insects are one of the taxa with the highest frequency of introduction due to their high diversity, biological properties, and close association with human activities. Here, the allodiversity of Italian entomofauna was analyzed, with a focus on Tuscany (Central Italy). A list of alien insects in Tuscany is included. The status of the alien entomofauna in Italy was updated. The number of alien insects amounts to 122 in Tuscany and 923 in Italy. An introduction rate of 98 species per decade was estimated in Italy. In Tuscany, alien insects belong to 10 orders, mostly Coleoptera (38%), Hemiptera (Sternorrhyncha and Auchenorrhyncha) (23%), and Hymenoptera (13%). They have been most often introduced through vegetable items (ornamental plants or crops). Most species come from the Nearctic region (26%) and are both phytophagous (63%) and amphigonic (80%). Differences and similarities in introduction patterns and in insect abundances across orders among regional, national, and European scales, also considering worldwide abundances, are discussed. Finally, a paucity of information regarding the negative impacts of many species, except for economic pests, phytosanitary threats, and vectors of disease, is underlined. A deeper understanding of the alien insects' ecological impact might help designate policies aimed at preventing further introductions and control the invasive populations of already established species.

Biological invasions: a field synopsis, systematic review, and database of the literature

Species introductions of anthropogenic origins are a major aspect of rapid ecological change globally. Research on biological invasions has generated a large literature on many different aspects of this phenomenon. Here, we describe and categorize some aspects of this literature, to better understand what has been studied and what we know, mapping well-studied areas and important gaps. To do so, we employ the techniques of systematic reviewing widely adopted in other scientific disciplines, to further the use of approaches in reviewing the literature that are as scientific, repeatable, and transparent as those employed in a primary study. We identified 2398 relevant studies in a field synopsis of the biological invasions literature. A majority of these studies (58%) were concerned with hypotheses for causes of biological invasions, while studies on impacts of invasions were the next most common (32% of the publications). We examined 1537 papers in greater detail in a systematic review. Superior competitive abilities of invaders, environmental disturbance, and invaded community species richness were the most common hypotheses examined. Most studies examined only a single hypothesis. Almost half of the papers were field observational studies. Studies of terrestrial invasions dominate the literature, with most of these concerning plant invasions. The focus of the literature overall is uneven, with important gaps in areas of theoretical and practical importance.

Gaps in border controls are related to quarantine alien insect invasions in Europe

Alien insects are increasingly being dispersed around the world through international trade, causing a multitude of negative environmental impacts and billions of dollars in economic losses annually. Border controls form the last line of defense against invasions, whereby inspectors aim to intercept and stop consignments that are contaminated with harmful alien insects. In Europe, member states depend on one another to prevent insect introductions by operating a first point of entry rule – controlling goods only when they initially enter the continent. However, ensuring consistency between border control points is difficult because there exists no optimal inspection strategy. For the first time, we developed a method to quantify the volume of agricultural trade that should be inspected for quarantine insects at border control points in Europe, based on global agricultural trade of over 100 million distinct origin-commodity-species-destination pathways. This metric was then used to evaluate the performance of existing border controls, as measured by border interception results in Europe between 2003 and 2007. Alarmingly, we found significant gaps between the trade pathways that should be inspected and actual number of interceptions. Moreover, many of the most likely introduction pathways yielded none or very few insect interceptions, because regular interceptions are only made on only a narrow range of pathways. European countries with gaps in border controls have been invaded by higher numbers of quarantine alien insect species, indicating the importance of proper inspections to prevent insect invasions. Equipped with an optimal inspection strategy based on the underlying risks of trade, authorities globally will be able to implement more effective and consistent border controls.

Is the expansion of the pine processionary moth, due to global warming, impacting the endangered Spanish moon moth through an induced change in food quality?

Recent climate change is known to affect the distribution of a number of insect species, resulting in a modification of their range boundaries. In newly colonized areas, novel interactions become apparent between expanding and endemic species sharing the same host. The pine processionary moth is a highly damaging pine defoliator, extending its range northwards and upwards in response to winter warming. Its expansion in the Alps has resulted in an invasion into the range of the Spanish moon moth, a red listed species developing on Scots pine. Pine processionary moth larvae develop during winter, preceding those of the moon moth, which hatch in late spring. Using pine trees planted in a clonal design, we experimentally tested the effect of previous winter defoliation by pine processionary moth larvae upon the survival and development of moon moth larvae. Feeding on foliage of heavily defoliated trees (>50%) resulted in a significant increase in the development time of moon moth larvae and a decrease in relative growth rate compared to feeding on foliage of undefoliated trees. Dry weight of pupae also decreased when larvae were fed with foliage of defoliated trees, and might, therefore, affect imago performances. However, lower defoliation degrees did not result in significant differences in larval performances compared to the control. Because a high degree of defoliation by pine processionary moth is to be expected during the colonization phase, its arrival in subalpine pine stands might affect the populations of the endangered moon moth.

Spatial genetic structure of the mountain pine beetle (Dendroctonus ponderosae) outbreak in western Canada: historical patterns and contemporary dispersal

Environmental change has a wide range of ecological consequences, including species extinction and range expansion. Many studies have shown that insect species respond rapidly to climatic change. A mountain pine beetle epidemic of record size in North America has led to unprecedented mortality of lodgepole pine, and a significant range expansion to the northeast of its historic range. Our goal was to determine the spatial genetic variation found among outbreak population from which genetic structure, and dispersal patterns may be inferred. Beetles from 49 sampling locations throughout the outbreak area in western Canada were analysed at 13 microsatellite loci. We found significant north-south population structure as evidenced by: (i) Bayesian-based analyses, (ii) north-south genetic relationships and diversity gradients; and (iii) a lack of isolation-by-distance in the northernmost cluster. The north-south structure is proposed to have arisen from the processes of postglacial colonization as well as recent climate-driven changes in population dynamics. Our data support the hypothesis of multiple sources of origin for the outbreak and point to the need for population specific information to improve our understanding and management of outbreaks. The recent range expansion across the Rocky Mountains into the jack/lodgepole hybrid and pure jack pine zones of northern Alberta is consistent with a northern British Columbia origin. We detected no loss of genetic variability in these populations, indicating that the evolutionary potential of mountain pine beetle to adapt has not been reduced by founder events. This study illustrates a rapid range-wide response to the removal of climatic constraints, and the potential for range expansion of a regional population.

Molecular and morphological characterisation of Pseudococcidae surveyed on crops and ornamental plants in Spain

Mealybugs (Hemiptera: Pseudococcidae) are common invasive pests in Europe, causing major problems on crops and ornamental plants. However, very few data are available concerning the mealybug fauna of southern Europe. This lack of data and the difficulty of identifying mealybugs morphologically by traditional techniques currently limit the perspectives for efficient specific pest management. The aim of this study was to provide multi-criterion characterization of mealybugs surveyed in eastern Spain in order to facilitate their routine identification through DNA sequencing or the use of derived species-specific molecular tools. We characterised 33 mealybug populations infesting crops and ornamental plants in eastern Spain, using a combination of molecular and morphological techniques, including the sequencing of the universal barcode DNA region cytochrome c oxidase subunit I (COI). This characterisation has led to the identification of ten species and provides sequence data for three previously unsequenced species, contributing to the phylogenetic knowledge of the family Pseudococcidae. In addition, the intraspecific variations found in the populations of five mealybug species provide insight into their invasion history.

Behavioral plasticity mediates asymmetric competition between invasive wasps and native ants

One of the most successful invasive species is the common wasp, Vespula vulgaris. We recently reported how foragers of this species have adopted previously unknown interference behavior when competing for food with native ants. Picking their opponents up in their mandibles, flying backward and dropping them some distance away from the disputed resource, wasps were shown to efficiently deal with a yet aggressive competitor and to modulate this behavior according to circumstances. Here we further discuss the nature and functioning of this unusual strategy. We first highlight the questions this interaction raises regarding the competitive advantages offered by asymmetries in body size and flight ability. Then, we argue that this study system illustrates the important role of behavioral plasticity in biological invasions; not only in the success of invaders but also in the ability of native species to coexist with these invaders.