Mapping species spatial distribution using spatial inference and prediction requires a lot of data. Occurrence data are generally not easily available from the literature and are very time-consuming to collect in the field. For that reason, we designed a survey to explore to which extent large-scale databases such as Google maps and Google street view could be used to derive valid occurrence data. We worked with the Pine Processionary Moth (PPM) Thaumetopoea pityocampa because the larvae of that moth build silk nests that are easily visible. The presence of the species at one location can therefore be inferred from visual records derived from the panoramic views available from Google street view. We designed a standardized procedure allowing evaluating the presence of the PPM on a sampling grid covering the landscape under study. The outputs were compared to field data. We investigated two landscapes using grids of different extent and mesh size. Data derived from Google street view were highly similar to field data in the large-scale analysis based on a square grid with a mesh of 16 km (96% of matching records). Using a 2 km mesh size led to a strong divergence between field and Google-derived data (46% of matching records). We conclude that Google database might provide useful occurrence data for mapping the distribution of species which presence can be visually evaluated such as the PPM. However, the accuracy of the output strongly depends on the spatial scales considered and on the sampling grid used. Other factors such as the coverage of Google street view network with regards to sampling grid size and the spatial distribution of host trees with regards to road network may also be determinant.

Sous les latitudes tempérées, les aires de distribution respectives des espèces d’insectes sont généralement conditionnées par les températures hivernales au travers de seuils minimaux de tolérance pour la survie et le développement. Ainsi, le déplacement des aires de répartition est un des effets les plus notables du réchauffement climatique sur les espèces sensibles au froid. Cependant, les conséquences de la colonisation de nouveaux milieux par les espèces en expansion, notamment sur les interactions interspécifiques restent largement inexplorées. La processionnaire du pin est un ravageur d’origine méditerranéenne, dont l’aire de répartition s’est considérablement étendue vers le nord et en altitude ces deux dernières décennies. Cette expansion est liée à la hausse des températures hivernales qui permet une meilleure survie des colonies se développant durant cette période. Notre étude s’est développée autour de deux axes de recherches : (1) la réponse des ennemis naturels à l’expansion de leur hôte ; (2) l’impact de la colonisation sur une espèce protégée inféodée à la même ressource alimentaire, l’Isabelle de France. Nos résultats ont montré que dans les zones nouvellement colonisées, la processionnaire du pin est libérée de la pression de ses parasitoïdes oophages. Ainsi, au niveau du front d’expansion, une femelle de processionnaire du pin produira plus de descendants que dans le coeur de son aire de répartition. De plus, la défoliation par la processionnaire du pin a un effet négatif sur le développement des chenilles d’Isabelle de France. Nos résultats contribuent à comprendre les causes de l’expansion de ce ravageur forestier et ses conséquences sur les espèces autochtones des zones nouvellement colonisées.

Although climate change is currently affecting the distribution of many species, insects are particularly impacted because of their high sensitivity to temperature. The pine processionary moth, Thaumetopoea pityocampa, is a forest insect extending its distribution in response to climate warming. Some pioneer colonies were recently detected far beyond the main range, near Paris and in eastern France. This study tracked the origin and pathways of these pioneer colonies through a combined use of genetic markers, measurement of female flight capabilities, and comparative analyses of the natural enemy complexes. This study also aimed to determine the establishment capability beyond the main range, considering the survival rate during two recent cold periods. The larval survival rate was higher in pioneer colonies (which behave like urban heat islands) than in main range. The flight capacity of females would not have allowed them to come from the main range or the nearest established colonies, and molecular tools further showed that individuals from at least three pioneer colonies were not assigned or similar to individuals at the edge of the main range. Egg parasitoids were absent while pupal parasitoids were present in the pioneer colonies suggesting an introduction at the pupal stage. These approaches provided strong evidence that this species has been accidentally moved near Paris and to eastern France, supporting the hypothesis of human-mediated transportation over natural dispersal. This type of dispersal was unexpected because of risks from urticating hairs and the easy detection of the species.

La cartographie de la distribution geographique des especes est importante pour suivre l’evolution des aires de distribution d’especes invasives ou d’especes natives en expansion geographique. Malheureusement, les donnees necessaires sont parfois difficilement accessibles a partir de la litterature et sont couteuses a collecter sur le terrain. Pour cette raison, nous avons concu une etude dans le but d'explorer dans quelle mesure il est possible d’utiliser les bases de donnees telles que Google Street View (GSV) pour obtenir des donnees d’occurrence valides. Nous avons choisi de travailler avec une espece d’insecte, la chenille processionnaire du pin (PP) Thaumetopoea pityocampa car les larves de cette espece se developpent dans le feuillage des arbres hotes et tissent un nid blanc aisement visible. La presence de l'espece dans un site donne peut donc etre facilement renseignee en examinant les vues panoramiques disponibles pour de nombreuses localites dans la base de donnees de Google Street View. Nous avons concu une procedure standardisee permettant d'evaluer la presence de la PP a partir des donnees GSV et nous l’avons mise en oeuvre sur une aire d’etude couvrant 46 848 km2dans la region Centre en France. La distribution de l’espece a egalement ete decrite a l’aide d’echantillonnages realises sur le terrain. Les donnees issues de l’examen des images Google Street View ont ete comparees aux donnees de terrain et se sont revelees de bons estimateurs de la presence de la processionnaire du pin avec une precision (proportion de valeurs correctement estimees) de 92.9% sur notre zone d’etude pour un maillage de 16 km x 16 km. Ces resultats suggerent que l’exploitation des bases de donnees de GSV pourrait permettre de produire des donnees ecologiques interessantes pour les especes dont la presence peut etre estimee visuellement a partir de photographies. Des etudes complementaires sont cependant necessaires pour mieux cerner la gamme d’echelles spatiales auxquelles GSV fournit des donnees d’occurrence fiables.

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

Climate change is currently affecting the distribution of many species and the underlying mechanism is particularly well understood for the pine processionary moth, Thaumetopoea pityocampa (Den. & Schiff.) (Lep., Notodontidae). Increased temperature in winter enhances the larval feeding activity and the colony survival. Therefore, the moth can extent its distribution on new areas at a rate depending on the female flying ability. Although the heated island in Paris vicinity was highly favorable for the species survival, this area was too far from the closest infested area to be colonized. However, some isolated colonies were recently discovered in this region, far beyond the natural expansion range. This study was intended to track the origin and pathways of these geographically isolated populations through a combined use of genetic markers, measurement of female flight capabilities, and comparative analyses of the natural enemy complexes. In addition, the potential rate of survival of the populations in the past was reconstructed. The effects of the recent winter cold waves were compared between isolated moth populations and naturally expanding populations. All these approaches provide strong evidence that the pine processionary moth has been accidentally moved to the Paris vicinity. With climate warming, this insect can potentially survive in new areas, and the Paris vicinity is more favorable for winter survival during cold waves. The flight capabilities of females are far lower than the distance between these isolated colonies and the natural distribution, and populations in these isolated colonies are genetically different from the ones at the edge of the distribution, suggesting a human-mediated transportation. Egg parasitoids are absent from isolated populations whereas larval parasitoids are present, suggesting an introduction at the pupal stage, probably along with the trade of large trees.