Regards méthodologiques sur l’échantillonnage des coléoptères saproxyliques au moyen des pièges-vitres

Saproxylic beetles are species-rich, mostly small and cryptic, and difficult to sample. Different methods are traditionally used to collect saproxylic beetles. These are (i) direct active collection techniques, (ii) rearing techniques and (iii) mass trapping methods. Window-flight trapping is currently the most frequently used technique for catching flying active saproxylic beetles. Thanks to the combination of different trap principles, window-fl ight trap devices may differ by a large number of intrinsic parameters. This paper offers further insight into the infl uence of 3 trap factors on the catches of dead wood associated beetles, by comparing (i) cross-vanes or single-plane WFT (shape effect), (ii) black or transparent CWFT (silhouette effect), (iii) low or high CWFT (height effect). Six ecological data sets from French upland or lowland, deciduous or coniferous forests, with paired freely hanging window traps on each plot, were compiled in this study and analysed with a methodological point of view to compare the efficiency of sampling methods. Trap shape had a signifi cant and strong effect on the abundance and species richness of saproxylic beetles. The single-plane traps caught a higher number of individuals and species. Nevertheless, given time/cost constraints, cross-vanes traps are recommended. Our study shows that black and transparent cross-vanes traps yielded similar saproxylic samples in terms of abundance, richness and overall composition. Our results confirm the vertical differentiation of saproxylic beetle assemblage. They suggest that low cross-vanes window traps yield more species-rich and individual-rich samples than canopy traps. Except Melyrids, no abundant species showed a strong association with top traps. Further optimisation analyses based on larger datasets are required to make sampling methods more reliableLes coléoptères saproxyliques constituent un groupe riche en espèces, souvent petites et cryptiques, et difficiles à échantillonner. Différentes méthodes sont traditionnellement utilisées pour les collecter: les techniques (i) de collecte active, (ii) d'élevage et (iii) de piégeage. Le piège-vitre est actuellement la méthode la plus fréquemment utilisée pour la capture des coléoptères saproxyliques aériens mobiles. Grâce à la combinaison de différents principes, les pièges-vitres comportent de multiples modèles. Cette étude concerne l'influence de 3 facteurs sur les captures de coléoptères saproxyliques, en comparant (i) des pièges plans bidirectionnels ou multidirectionnels en croix (effet de forme), (ii) des pièges transparents ou noirs (effet silhouette), (iii) des pièges suspendus à faible hauteur ou dans la canopée. Six jeux de données écologiques de plaine ou d'altitude, de forêts françaises feuillues ou résineuses, et comportant deux pièges différents appariés parplacette, ont été compilés et analysés pour comparer l'efficacité respective des méthodes. La forme du piège a un fort effet significatif sur l'abondance et la richesse spécifique, à l'avantage des pièges plans. Néanmoins, en raison de contraintes pratiques ou financières, les pièges-croix sont recommandés. Les pièges noirs ou transparents fournissent des échantillons comparables en termes d'abondance, de richesse et de composition. Nos résultats confirment la différenciation verticale des assemblages de coléoptères saproxyliques, les pièges bas capturant davantage d'individus et d'espèces que les pièges de la canopée. A l'exception des Melyridae, aucune espèce n'est associée aux strates hautes. Des analyses complémentaires fondées sur de plus amples jeux de données sont requises pour optimiser les méthodes d'échantillonnage

Bark beetles and pinhole borers recently or newly introduced to France (Coleoptera: Curculionidae, Scolytinae and Platypodinae)

We present an annotated list of 11 Scolytinae and Platypodinae species newly or recently introduced to France. Four species are recorded for the first time as interceptions: Euplatypus hintzi (Schaufuss), Euplatypus parallelus (Fabricius), Xyleborus affinis Eichhoff and Xyleborus ferrugineus (Fabricius). Two are possibly naturalised: Xyleborus bispinatus Eichhoff and Cryphalus dilutus Eichhoff, while Cyclorhipidion distinguendum (Eggers) and Xyloterinus politus (Say) are confirmed as species newly established in Europe. Moreover, an unidentified species of Amasa Lea, collected previously in Spain, is recorded for the first time in France: Amasa sp. near truncata (Erichson). We point out that literature references to Amasa truncata as an invasive species in New Zealand and South America are incorrect, as the photographs of these non-native populations do not match the holotype of A. truncata. For each species we have updated its global distribution, detailed all French records, and summarized biology, ecology, host trees and potential risks as pests

A test for assessment of saproxylic beetle biodiversity using subsets of monitoring species

In European forests, large scale biodiversity monitoring networks need to be implemented - networks which include components such as taxonomical groups that are at risk and that depend directly on forest stand structure. In this context, monitoring the species-rich group of saproxylic beetles is challenging. In the absence of sufficient resources to comprehensively survey a particular group, surrogates of species richness can be meaningful tools in biodiversity evaluations. In search of restricted subsets of species to use as surrogates of saproxylic beetle richness, we led a case study in Western Europe. Beetle data were compiled from 67 biodiversity surveys and ecological studies carried out from 1999 to 2010 with standardized trapping methods in France and Belgium. This large-scale dataset contains 642 forest plots, 1521 traps and 856 species. Twenty-two simplified species subsets were identified as potential surrogates, as well as the number of genera, a higher taxonomic level, taking into account, for each surrogate, the effort required for species identification, the practical monitoring experience necessary, the species conservation potential or the frequency of species occurrence. The performance of each surrogate was analyzed based on the following parameters: overall surrogacy (correlation between subset richness and total species richness), surrogacy vs. identification cost balance, surrogacy variation over a wide range of ecological conditions (forest type, altitude, latitude and bio-geographical area) and consistency with spatial scale. Ecological representativeness and ability to monitor rare species were supplementary criteria used to assess surrogate performance. The subsets consisting of the identifiable (or only easy-to-identify species) could easily be applied in practice and appear to be the best performing subsets, from a global point of view. The number of genera showed good prediction at the trap level and its surrogacy did not vary across wide environmental gradients. However, the subset of easy-to-identify species and the genus number were highly sensitive to spatial scale, which limits their use in large-scale studies. The number of rare species or the species richness of single beetle families (even the best single-family subset, the Cerambycidae) were very weak surrogates for total species richness. Conversely, the German list of monitoring species had high surrogacy, low identification costs and was not strongly influenced by the main geographical parameters, even with our French and Belgian data. In European-wide monitoring networks, such internationally validated subsets could be very useful with regard to the timing and cost-efficiency of field inventories

Responses of the hyper‐diverse community of canopy‐dwelling Hymenoptera to oak decline

The data that support the findings of this study are openly available in Recherche Data Gouv at https://entrepot.recherche.data.gouv.fr/dataset.xhtml?persistentId=doi:10.57745/H8CBG1. Representative specimens of Braconidae, Ichneumonidae, Halictidae, Andrenidae, Crabronidae and Pemphredonidae are housed at the Orléans Museum for Biodiversity and Environment (MOBE, Orléans, France).International audience1. Forest decline and dieback are growing phenomena worldwide, resulting in severe, large-scale degradation of the canopy. This can profoundly alter the provision of trophic resources and microhabitats for canopy-dwelling arthropods.2. In 2019, we assessed the effect of oak decline on the community of canopy-dwelling Hymenoptera. We selected 21 oak stands and 42 plots, located in three forests in France, presenting contrasting levels of decline. Insects were sampled at the canopy level with green multi-funnel and flight-interception traps.3. We collected a particularly diverse community of 19,289 insect individuals belonging to 918 taxa, 10 larval trophic guilds and 7 nesting guilds.4. Oak decline had no effect on the abundance or richness of the overall community but significantly reshaped the community assemblages. Decline had contrasting effects depending on the taxa and guilds considered. Specialist parasitoids were more abundant at intermediate levels of decline severity while generalists were negatively affected. Taxa depending on ground-related resources and microhabitats were promoted. Saproxylic taxa were more abundant while xylophagous insects were negatively impacted.5. Reduced leaf area index promoted several guilds and the diversity of the overall community. While an increasing tree mortality rate enhanced the abundance and diversity of deadwood resources, it had negative impacts on several Hymenoptera guilds. Our results suggest that micro-environmental changes at the ground level due to canopy decline have major cascading effects on the communities of canopy-dwelling Hymenoptera.6. Our study highlights the relevance of studying Hymenoptera communities to investigate the outcomes of disturbances on forest biodiversity