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1.The invasive yellow-legged hornet was first discovered in Europe, in south-western France, in 2004. It has since spread very rapidly and has caused significant mortality among honey bees and native entomofauna. It also poses a risk to humans because its sting provokes allergic reactions. The objectives of this study were the following: (i) to disentangle the roles played by human-mediated dispersal and self-mediated dispersal in the species’ rapid range expansion and (ii) to estimate the intensity of control measures in France and determine what needs to be done to slow the hornet's spread and dramatically reduce its population densities. 2.A mathematical model was developed to describe the hornet's potential spread. This model included parameters describing the population growth rate, carrying capacity, self-mediated dispersal, human-mediated dispersal and the efficacy of control measures (i.e. the destruction of detected nests). Model parameters were estimated using 2004–2009 occurrence data for France and the model was then validated using 2013 occurrence data. Several scenarios were tested: human-mediated dispersal was present or absent and control intensity varied. Then, the species’ spread in coming years was simulated (from 2013 to 2020). 3.Despite some uncertainty on the value of the parameters, this model is relatively robust. Human-mediated dispersal may not be necessarily responsible for the hornet's rapid range expansion; the species could spread rapidly on its own. It is likely that, to date, an average of 30–40% of detected nests have been destroyed each year. 4.Increasing the percentage of destroyed nests from 30 to 60% could reduce the species’ spread by 17% and its nest density by 29%. If 95% of nests are destroyed, the species’ spread and nest density could decline by 43% and 53%, respectively. 5.Synthesis and applications. The mathematical model developed in this study shows that human-mediated dispersal of the invasive yellow-legged hornet may not be the only factor explaining the hornet's rapid range expansion and that controlling this invasive pest is still possible. Therefore, there is an urgent need to reduce self-mediated dispersal and to intensify and improve control measures to diminish the species’ impact and prevent its further spread. Control measures could combine the mechanical removal and destruction of individuals or infested materials with biological control techniques.

The proliferation of DNA data is revolutionizing all fields of systematic research. DNA barcode sequences, now available for millions of specimens and several hundred thousand species, are increasingly used in algorithmic species delimitations. This is complicated by occasional incongruences between species and gene genealogies, as indicated by situations where conspecific individuals do not form a monophyletic cluster in a gene tree. In two previous reviews, non-monophyly has been reported as being common in mitochondrial DNA gene trees. We developed a novel web service “Monophylizer” to detect non-monophyly in phylogenetic trees and used it to ascertain the incidence of species non-monophyly in COI (a.k.a. cox1) barcode sequence data from 4977 species and 41,583 specimens of European Lepidoptera, the largest data set of DNA barcodes analyzed from this regard. Particular attention was paid to accurate species identification to ensure data integrity. We investigated the effects of tree-building method, sampling effort, and other methodological issues, all of which can influence estimates of non-monophyly. We found a 12% incidence of non-monophyly, a value significantly lower than that observed in previous studies. Neighbor joining (NJ) and maximum likelihood (ML) methods yielded almost equal numbers of non-monophyletic species, but 24.1% of these cases of non-monophyly were only found by one of these methods. Non-monophyletic species tend to show either low genetic distances to their nearest neighbors or exceptionally high levels of intraspecific variability. Cases of polyphyly in COI trees arising as a result of deep intraspecific divergence are negligible, as the detected cases reflected misidentifications or methodological errors. Taking into consideration variation in sampling effort, we estimate that the true incidence of non-monophyly is ∼23%, but with operational factors still being included. Within the operational factors, we separately assessed the frequency of taxonomic limitations (presence of overlooked cryptic and oversplit species) and identification uncertainties. We observed that operational factors are potentially present in more than half (58.6%) of the detected cases of non-monophyly. Furthermore, we observed that in about 20% of non-monophyletic species and entangled species, the lineages involved are either allopatric or parapatric—conditions where species delimitation is inherently subjective and particularly dependent on the species concept that has been adopted. These observations suggest that species-level non-monophyly in COI gene trees is less common than previously supposed, with many cases reflecting misidentifications, the subjectivity of species delimitation or other operational factors.

Pine wilt disease (PWD), caused by pine wood nematode (PWN), poses a tremendous threat to global pine forests because it can result in rapid and widespread infestations within months, leading to large-scale tree mortality. Therefore, the implementation of preventive measures relies on early detection of PWD. Unmanned aerial vehicle (UAV)-based hyperspectral images (HSI) can detect tree-level changes and are thus an effective tool for forest change detection. However, previous studies mainly used single-date UAV-based HSI data, which could not monitor the temporal changes of disease distribution and determine the optimal detection period. To achieve these purposes, multi-temporal data is required. In this study, Pinus koraiensis stands were surveyed in the field from May to October during an outbreak of PWD. Concurrently, multi-temporal UAV-based red, green, and blue bands (RGB) and HSI data were also obtained. During the survey, 59 trees were confirmed to be infested with PWD, and 59 non-infested trees were used as control. Spectral features of each tree crown, such as spectral reflectance, first and second-order spectral derivatives, and vegetation indices (VIs), were analyzed to identify those useful for early monitoring of PWD. The Random Forest (RF) classification algorithm was used to examine the separability between the two groups of trees (control and infested trees). The results showed that: (1) the responses of the tree crown spectral features to PWD infestation could be detected before symptoms were noticeable in RGB data and field surveys; (2) the spectral derivatives were the most discriminable variables, followed by spectral reflectance and VIs; (3) based on the HSI data from July to October, the two groups of trees were successfully separated using the RF classifier, with an overall classification accuracy of 0.75–0.95. Our results illustrate the potential of UAV-based HSI for PWD early monitoring.

The advent of simple and affordable tools for molecular identification of novel insect invaders and assessment of population diversity has changed the face of invasion biology in recent years. The widespread application of these tools has brought with it an emerging understanding that patterns in biogeography, introduction history and subsequent movement and spread of many invasive alien insects are far more complex than previously thought. We reviewed the literature and found that for a number of invasive insects, there is strong and growing evidence that multiple introductions, complex global movement, and population admixture in the invaded range are commonplace. Additionally, historical paradigms related to species and strain identities and origins of common invaders are in many cases being challenged. This has major consequences for our understanding of basic biology and ecology of invasive insects and impacts quarantine, management and biocontrol programs. In addition, we found that founder effects rarely limit fitness in invasive insects and may benefit populations (by purging harmful alleles or increasing additive genetic variance). Also, while phenotypic plasticity appears important post-establishment, genetic diversity in invasive insects is often higher than expected and increases over time via multiple introductions. Further, connectivity among disjunct regions of global invasive ranges is generally far higher than expected and is often asymmetric, with some populations contributing disproportionately to global spread. We argue that the role of connectivity in driving the ecology and evolution of introduced species with multiple invasive ranges has been historically underestimated and that such species are often best understood in a global context.

Globalization is triggering an increase in the establishment of alien insects in Europe, with several species having substantial ecological and economic impacts. We investigated long-term changes in rates of species spread following establishment. We used the total area of countries invaded by 1171 insect species for which the date of first record in Europe is known, to estimate their current range radius (calculated as [invaded area](0.5)/pi). We estimated initial rates of radial spread and compared them among different groups of insects for all years (1800-2014) and for a subset of more recent decades (1950-2014). Accidentally introduced species spread faster than intentionally introduced species. Considering the whole period 1800-2014, spread patterns also differ between feeding guilds, with decreasing spread rates over residence time in herbivores but not in detritivores or parasitic species. These decreases for herbivorous species appeared mainly in those associated with herbaceous plants and crops rather than woody plants. Initial spread rate was significantly greater for species detected after 1990, roughly 3-4 times higher than for species that arrived earlier. We hypothesize that the political changes in Europe following the collapse of the Iron Curtain in 1989, and the further dismantling of customs checkpoints within an enlarged European Union (EU) have facilitated the faster spread of alien insect species. Also, the number of species first recorded in the Eastern Bloc of the politically-divided Europe before 1989 was lower than for the rest of Europe. A detailed analysis of six recent invaders indicated a dominant role of long-distance translocations related to human activities, especially with the plant trade, in determining rates of spread.

The invasive yellow-legged hornet, Vespa velutina nigrithorax Lepeletier, 1836 (Hymenoptera: Vespidae), is native to Southeast Asia. It was first detected in France (in the southwest) in 2005. It has since expanded throughout Europe and has caused significant harm to honeybee populations. We must better characterize the hornet's flight capacity to understand the species' success and develop improved control strategies. Here, we carried out a study in which we quantified the flight capacities of V. velutina workers using computerized flight mills. We observed that workers were able to spend around 40% of the daily 7-hour flight tests flying. On average, they flew 10km to 30km during each flight test, although there was a large amount of variation. Workers sampled in early summer had lower flight capacities than workers sampled later in the season. Flight capacity decreased as workers aged. However, in the field, workers probably often die before this decrease becomes significant. During each flight test, workers performed several continuous flight phases of variable length that were separated by rest phases. Based on the length of those continuous flight phases and certain key assumptions, we estimated that V. velutina colony foraging radius is at least 700 m (half that in early summer); however, some workers are able to forage much farther. While these laboratory findings remain to be confirmed by field studies, our results can nonetheless help inform V. velutina biology and control efforts.

Background: The geometrid moths of Europe are one of the best investigated insect groups in traditional taxonomy making them an ideal model group to test the accuracy of the Barcode Index Number (BIN) system of BOLD (Barcode of Life Datasystems), a method that supports automated, rapid species delineation and identification. Methodology/Principal Findings: This study provides a DNA barcode library for 219 of the 249 European geometrid moth species (88%) in five selected subfamilies. The data set includes COI sequences for 2130 specimens. Most species (93%) were found to possess diagnostic barcode sequences at the European level while only three species pairs (3%) were genetically indistinguishable in areas of sympatry. As a consequence, 97% of the European species we examined were unequivocally discriminated by barcodes within their natural areas of distribution. We found a 1:1 correspondence between BINs and traditionally recognized species for 67% of these species. Another 17% of the species (15 pairs, three triads) shared BINs, while specimens from the remaining species (18%) were divided among two or more BINs. Five of these species are mixtures, both sharing and splitting BINs. For 82% of the species with two or more BINs, the genetic splits involved allopatric populations, many of which have previously been hypothesized to represent distinct species or subspecies. Conclusions/Significance: This study confirms the effectiveness of DNA barcoding as a tool for species identification and illustrates the potential of the BIN system to characterize formal genetic units independently of an existing classification. This suggests the system can be used to efficiently assess the biodiversity of large, poorly known assemblages of organisms. For the moths examined in this study, cases of discordance between traditionally recognized species and BINs arose from several causes including overlooked species, synonymy, and cases where DNA barcodes revealed regional variation of uncertain taxonomic significance.

A literature survey identified 403 primary research publications that investigated the ecological effects of invasive alien insects and/or the mechanisms underlying these effects. The majority of these studies were published in the last 8 years and nearly two-thirds were carried out in North America.These publications concerned 72 invasive insect species, of which two ant species, Solenopsis invicta and Linepithema humile, accounted for 18% and 14% of the studies, respectively.Most publications investigated effects on native biodiversity at population or community level. Genetic effects and, to a lesser extent, effects on ecosystem services and processes were rarely explored. We review the effects caused by different insect invaders according to: their ecosystem roles, i.e. herbivores, predators, parasites,parasitoids and pollinators; the level of biological organisation at which they occur; and the direct and indirect mechanisms underlying these effects. The best documented effects occur in invasive ants,Eurasian forest herbivores invasive in North America,and honeybees. Impacts may occur through simple trophic interactions such as herbivory, predation or parasitism. Alien species may also affect native species and communities through more complex mechanisms such as competition for resources,disease transmission, apparent competition, or pollination disruption, among others. Finally, some invasive insects, particularly forest herbivores and ants, are known to affect ecosystem processes through cascading effects. We identify biases and gaps in our knowledge of ecological effects of invasive insects and suggest further opportunities for research.

Climate warming is inducing dramatic changes in species distribution. While many studies report the poleward range expansion of some species, some others report the range retraction and extinction risk of other species. Here we explore how climate warming affects the southern edge in North Africa of the pine processionary moth, Thaumetopoea pityocampa, which is a model insect currently expanding northwards and toward higher elevation in Europe. This Mediterranean forest insect was found in southern Tunisia until 2003. Field surveys were conducted to map the current southern edge of the species in Tunisia. Pheromone traps were installed on a north-south gradient, a translocation experiment of egg masses was conducted on this gradient, and local temperature change was analyzed. We thus proved that the pine processionary moth has disappeared from southern Tunisia, and that no more adult males were actually flying there. We also found a decrease of egg hatching and of the proportion of individuals able to reach larval stages along this gradient, while daily minimal and maximal temperatures globally increased. Furthermore, we showed that daily maximal and minimal temperatures as well as indices of extremely high temperatures have substantially increased during the study period (1980–2019). This study reveals the retraction of the pine processionary moth from southern Tunisia due to higher mortality rates that could be attributed to a significant local warming. The role of other factors (mainly the response of host trees and natural enemies to climate change) may amplify this direct effect and should be further explored.

The international seed trade is considered relatively safe from a phytosanitary point of view and is therefore less regulated than trade in other plants for planting. However, the pests carried by traded seeds are not well known. We assessed insects and fungi in 58 traded seed lots of 11 gymnosperm and angiosperm tree species from North America, Europe, and Asia. Insects were detected by X-raying and molecular methods. The fungal community was characterized using high-throughput sequencing (HTS) and by growing fungi on non-selective agar. About 30% of the seed lots contained insect larvae. Gymnosperms contained mostly hymenopteran (Megastigmus spp.) and dipteran (Cecidomyiidae) larvae, while angiosperms contained lepidopteran (Cydia latiferreana) and coleopteran (Curculio spp.) larvae. HTS indicated the presence of fungi in all seed lots and fungi grew on non-selective agar from 96% of the seed lots. Fungal abundance and diversity were much higher than insect diversity and abundance, especially in angiosperm seeds. Almost 50% of all fungal exact sequence variants (ESVs) found in angiosperms were potential pathogens, in comparison with around 30% of potentially pathogenic ESVs found in gymnosperms. The results of this study indicate that seeds may pose a greater risk of pest introduction than previously believed or accounted for. A rapid risk assessment suggests that only a small number of species identified in this study is of phytosanitary concern. However, more research is needed to enable better risk assessment, especially to increase knowledge about the potential for transmission of fungi to seedlings and the host range and impact of identified species.