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Identifying the invasion routes of non-native species is crucial to understanding invasions and customizing management strategies. The box tree moth, Cydalima perspectalis, is native to Asia and was recently accidentally introduced into Europe as a result of the ornamental plant trade. Over the last 15 years, it has spread across the continent and has reached the Caucasus and Iran. It is threatening Buxus trees in both urban areas and forests. To investigate the species’ invasion routes, native and invasive box tree moth populations were sampled, and moth’s genetic diversity and structure were compared using microsatellite markers. Our approximate Bayesian computation analyses strongly suggest that invasion pathways were complex. Primary introductions originating from eastern China probably occurred independently twice in Germany and once in the Netherlands. There were also possibly bridgehead effects, where at least three invasive populations may have served as sources for other invasive populations within Europe, with indication of admixture between the two primary invasive populations. The bridgehead populations were likely those in the countries that play a major role in the ornamental plant trade in Europe, notably Germany, the Netherlands, and Italy. All these invasion processes likely facilitated its fast expansion across Europe and illustrate the role played by the ornamental plant trade not only in the moth’s introduction from China but also in the species’ spread across Europe, leading to an invasion with a complex pattern.

Pesticide resistance development is an example of rapid contemporary evolution that poses immense challenges for agriculture. It typically evolves due to the strong directional selection that pesticide treatments exert on herbivorous arthropods. However, recent research suggests that some species are more prone to evolve pesticide resistance than others due to their evolutionary history and standing genetic variation. Generalist species might develop pesticide resistance especially rapidly due to pre-adaptation to handle a wide array of plant allelochemicals. Moreover, research has shown that adaptation to novel host plants could lead to increased pesticide resistance. Exploring such cross-resistance between host plant range evolution and pesticide resistance development from an ecological perspective is needed to understand its causes and consequences better. Much research has, however, been devoted to the molecular mechanisms underlying pesticide resistance while both the ecological contexts that could facilitate resistance evolution and the ecological consequences of cross-resistance have been under-studied. Here, we take an eco-evolutionary approach and discuss circumstances that may facilitate cross-resistance in arthropods and the consequences cross-resistance may have for plant-arthropod interactions in both target and non-target species and species interactions. Furthermore, we suggest future research avenues and practical implications of an increased ecological understanding of pesticide resistance evolution.

International audience; Simple SummaryThe box tree moth, Cydalima perspectalis, is an Asian pest whose rapid invasion in Europe causes considerable economic and ecological impacts. Larvae enter a winter diapause induced by photoperiod in both native and invaded ranges, but factors that trigger the return to an active phase are still unknown. Yet, identifying them is crucial to understanding how diapause end synchronizes with the end of the winter stress encountered in Europe. We tested whether activity resumption is regulated by thermal and/or photoperiodic thresholds, two factors often involved in diapause termination, by exposing diapausing caterpillars from an invaded area to crossed treatments at the laboratory. The evolution of diapause rate was monitored over time and compared to that of nearby field sites invaded. A strong positive effect of increasing temperature was found on the rate and dynamics of diapause termination, whereas no compelling effect of photoperiod appeared. Resuming development directly when main stressors fade, not in response to indirect photoperiodic cues that could be mismatched outside native areas, likely contributes to the good match observed between diapause and the new climates encountered in the invaded range. This finding can improve phenological modelling of the overwintering generation and help better mitigate its damage.AbstractThe association between indirect environmental cues that modulate insect diapause and the actual stressors is by no means granted when a species encounters new environments. The box tree moth, Cydalima perspectalis, is an Asian pest whose rapid invasion in Europe causes considerable economic and ecological impacts. Larvae enter a winter diapause induced by the photoperiod in both native and invaded ranges, but factors that trigger the return to an active phase are still unknown. Yet, identifying them is crucial to understand how diapause end synchronizes with the end of the winter stress encountered in Europe. To test whether activity resumption is regulated by thermal and/or photoperiodic thresholds, or additive effects between these factors often involved in diapause termination, diapausing caterpillars from an invaded area were exposed to crossed treatments at the laboratory. The evolution of diapause rate was monitored over time and compared to that of nearby field sites invaded. A strong positive effect of increasing temperature was found on the rate and dynamics of diapause termination, whereas no compelling effect of photoperiod appeared. Resuming development directly when main stressors fade, not in response to indirect photoperiodic cues that could be mismatched outside native areas, likely contributes to the good match observed between diapause and the new climates that this pest encountered in the invaded range.

Article en open access; International audience; In this study, we report the development of a set of 15 polymorphic microsatellite markers for the box tree moth, Cydalima perspectalis (Walker), a highly invasive insect in Europe causing significant damage to natural and ornamental Buxus trees. The markers were characterized for four distant populations in both its native (China, two populations) and invasive ranges (Czech Republic and Turkey, one population each). The number of alleles ranged from 2 to 12. No marker significantly deviated from the Hardy-Weinberg equilibrium for all the populations sampled. These microsatellite markers are promising tools for further studies on the invasive pathways and dispersal pattern of the box tree moth in Europe.

The box tree moth, Cydalima perspectalis, is an invasive insect that has rapidly colonised Europe, damaging to natural and ornamental box trees. In its native habitat in China, the number of generations per year is variable, but the number of generations observed in European climates remained unclear. This is a key issue for understanding the rapid increase in population size and range, and for optimising control. We developed a temperature- and photoperiod-driven model to simulate the life cycle of this insect and development rates for each life stage. The model was calibrated on published data and validated with observations obtained in France and Switzerland. Model stability analysis showed that minimal temperature for larval development to be the most important parameter to estimate. Diapause parameters had little effect. We then explored the effects of temperature increases of 1 and 2 °C. The number of generations ranged from two to four at the various study sites. Climate warming will accelerate the insect life cycle, making it possible for the occurrence of one more generation per year. The key finding of this study was the complexity of population dynamics for this species. Some generations overlapped, making it difficult to identify the adult flight period clearly for each generation. Furthermore, various stages were potentially able to overwinter, not just diapausing larvae. Climate warming may also enhance this phenomenon in the future. Further explorations of the complex dynamics of this species are required, notably it remains unclear how successfully the various life stages survive winter temperatures. Further model refinements are also required to obtain more accurate estimates of box tree moth phenology. However, this is the first phenology model for box tree moth to be published, and our findings provide useful information for improving control of this pest.

International audience; Many recently established non-native insect species appear to be spreading across Europe significantly faster than before. The box tree moth (Cydalima perspectalis), a native to Asia, is illustrative of this trend. First recorded in 2007 in Germany, the moth has then colonized in less than 10 years more than 30 countries in Europe and Asia Minor, causing significant damage to wild and ornamental Buxus trees. It has been hypothesized that the trade of ornamental box trees between China and Europe was responsible for the moth introduction while plant trade among European countries may have caused its rapid spread. To clarify the pest invasion history, we analyzed the genetic diversity and structure of its populations in the native and invaded ranges, using a 1495-bp fragment of the mitochondrial cytochrome oxidase I and II genes. Moth genetic diversity in Asia compared to the one observed in the invaded Europe and Asia Minor suggested that the invasive populations probably originated from eastern China. Furthermore, the high genetic diversity coupled with the spatial genetic structure in the invaded range suggested the occurrence of several introduction events, probably directly from China. Moreover, the spatial genetic structure in Europe and Asia Minor may also reflect secondary invasions within invaded range because of ornamental plant trade among European countries.

International audience; Background and Purpose: Box tree moth (Cydalima perspectalis: Lepidoptera, Crambidae) is an invasive species rapidly spreading through Europe and making considerable damage to native and planted European box plants (Buxus sp.). It has up to three generations per year and has no natural enemies in Europe which helps it to spread rapidly and to become highly invasive in its new range. The aim of this paper is to show i) spatial distribution, ii) number of generations; iii) food choice, and iv) genetic distribution of box tree moth in Croatia. Materials and Methods: Occurrence data of box tree moth were obtained by field observation and data obtained from the general public. The number of generations of box tree moth was studied by direct observation of life stages on plants. Food choice test was conducted on Buxus sempervirens, Ilex aquifolium, Euonymus japonicus and Ligustrum vulgare used as food plants. Haplotype diversity and distribution of box tree moth was done for 5 localities in Croatia and their comparison to the haplotypes from China, Korea and 10 European countries. Results: Box tree moth has rapidly spread over the whole territory of Croatia in 4 years and it has three generations per year. The larvae showed a clear preference for B. sempervirens leaves and the total consumption was 0.5 g/dry weight of box leaves/larva. Three haplotypes were observed and haplotype HT4 was found in 4 out of 5 sampling sites in Croatia. The haplotypes observed in Croatia were present in China, which indicates Chinese origin of Croatian populations. Conclusions: Suitable European climate, widely available host plants and lack of natural enemies have enabled box tree moth to become highly invasive, to quickly disperse in its new environment and to make devastating damages to ornamental European box plants and hedges.