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International audience; Edge contrast, is one of the main determinants of edge effects. This study examines the response of plant and pollinatordiversity (bees and butterflies) to forest edge contrast, i.e. the difference between forests and adjacent open habitats withdifferent disturbance regimes. We also investigated a potential cascading effect from plants to pollinators and whether edgestructure and landscape composition mediate the relationship between edge contrast and beta diversity of pollinators. Wesampled 51 low-contrast edges where forests were adjacent to habitats showing low levels of disturbance (i.e. grey dunes,mowed fire-breaks, orchards, grasslands) and 29 high-contrast edges where forests were adjacent to more intensively disturbedhabitats (i.e. tilled firebreaks, oilseed rape) in three regions of France. We showed that plant diversities were higher in edges thanin adjacent open habitat, whatever the edge contrast. However, plant beta diversity did not differ significantly between low andhigh-contrast edges. While we observed higher pollinator diversities in adjacent habitats than in low-contrast edges, there wereno significant differences in pollinator beta diversity depending on edge contrast. We did not observe a cascading effect from plants to pollinators. Plant and bee beta diversities were mainly explained by local factors (edge structure and flower cover)while butterfly beta diversity was explained by surrounding landscape characteristics (proportion of land cover in grassland).

Specialization is an important attribute of a biological control agent. The maritime pine bast scale,Matsucoccus feytaudiDucasse (Hemiptera Matsucoccidae), is an invasive species in Southeast France and the North of Italy.Iberorhyzobius rondensisEizaguirre (Coleoptera: Coccinellidae), is a recently described ladybird species. Both adults and larvae are predaceous, feeding on egg masses ofM. feytaudi, and are strongly attracted toM. feytaudi’s sex pheromone. To evaluate the potential ofI. rondensisas a biocontrol agent of the scale, we studied its niche breadth and prey range with emphasis on pine forests and hemipterans as tested prey. In this study,I. rondensiswas found to achieve complete development only when fed onM. feytaudiegg masses (92.9% survival) and an artificial prey: eggs ofEphestia kuehniellaZeller (27.6% survival). From the 2nd instar onwards, complete development could be achieved using other prey species, although larvae had significantly higher mortality and slower development. In choice tests,M. feytaudiwas the preferred prey. Surveys of the ladybird populations in the Iberian Peninsula revealed that it was found exclusively onPinus pinasterAiton, the sole host ofM. feytaudi. The unusual specialization ofI. rondensis, among other predaceous ladybirds, makes it an appropriate candidate for classical biological control ofM. feytaudi.

International audience; Bark beetles are notorious pests of natural and planted forests causing extensive damage. These insects depend on dead or weakened trees but can switch to healthy trees during an outbreak as mass-attacks allow the beetle to overwhelm tree defences. Climatic events like windstorms are known to favour bark beetle outbreaks because they create a large number of breeding sites, i.e., weakened trees and for this reason, windthrown timber is generally preventively harvested and removed. In December 1999, the southwest of France was struck by a devastating windstorm that felled more that 27 million m3of timber. This event offered the opportunity to study large-scale spatial pattern of trees attacked by the bark beetle Ips sexdentatus and its relationship with the spatial location of pine logs that were temporally stored in piles along stand edges during the post-storm process of fallen tree removal. The study was undertaken in a pure maritime pine forest of 1300 ha in 2001 and 2002. We developed a landscape approach based on a GIS and a complete inventory of attacked trees. During this study more than 70% of the investigated stands had at least one tree attacked by I. sexdentatus. Spatial aggregation prevailed in stands with n≥15 attacked trees. Patches of attacked trees were identified using a kernel estimation procedure coupled with randomization tests. Attacked trees formed patches of 500–700 m2 on average which displayed a clumped spatial distribution. Log piles stemming from the sanitation removals were mainly distributed along the large access roads and showed an aggregated spatial pattern as well. The spatial relationship between patches of attacked trees and log pile storage areas was analyzed by means of the Ripley’s statistic that revealed a strong association at the scale of the studied forest. Our results indicated that bark beetle attacks were facilitated in the vicinity of areas where pine logs were stored. The spatial extent of this relationship was >1000 m. Similar results were obtained in 2001 and 2002 despite differences in the number and spatial distribution of attacked trees. The presence of a strong “facilitation effect” suggests that log piles should be removed quickly in order to prevent outbreaks of bark beetles.

International audience; Several pine bast scales (Hemiptera: Matsucoccidae) are important pests of pine trees in the Northern Hemisphere. Some species are invasive and cause significant economic and environmental impacts. Such is the case with Matsucoccus feytaudi Ducasse, an invasive pest of maritime pine forests in Southeastern France, Italy, and Corsica. The ladybird Iberorhyzobius rondensis (Eizaguirre) is a recently described species that is endemic to the Iberian Peninsula and is a potential candidate for the biological control of M. feytaudi. However, little is known of the biology of I. rondensis. As part of the risk assessment study for a classical biological control program, the phenology and reproductive mechanisms of the beetle were analyzed. I. rondensis is univoltine and is seasonally synchronized with the phenology of the prey M. feytaudi, which is also univoltine. An obligatory reproductive diapause of 5–6 mo and the need to feed on the eggs of the prey to begin oviposition emerged as the two primary mechanisms that assure life cycle synchronization of the ladybird with its prey. Female fecundity was also higher when the ladybirds were fed M. feytaudi eggs. Life cycle synchronization with M. feytaudi and reproduction triggered by consumption of prey eggs indicate that I. rondensis is a promising biological control agent of the pine bast scale.

Energy allocation strategies have been widely documented in insects and were formalized in the context of the reproduction process by the terms ‘capital breeder’ and ‘income breeder’. We propose here the extension of this framework to dispersal ability, with the concepts of ‘capital disperser’ and ‘income disperser’, and explore the trade-off in resource allocation between dispersal and reproduction. We hypothesized that flight capacity was sex-dependent, due to a trade-off in energy allocation between dispersal and egg production in females. We usedMonochamus galloprovincialisas model organism, a long-lived beetle which is the European vector of the pine wood nematode. We estimated the flight capacity with a flight mill and used the number of mature eggs as a proxy for the investment in reproduction. We used the ratio between dry weights of the thorax and the abdomen to investigate the trade-off. The probability of flying increased with the adult weight at emergence, but was not dependent on insect age or sex. Flight distance increased with age in individuals but did not differ between sexes. It was also positively associated with energy allocation to thorax reserves, which increased with age. In females, the abdomen weight and the number of eggs also increase with age with no negative effect on flight capacity, indicating a lack of trade-off. This long-lived beetle has a complex strategy of energy allocation, being a ‘capital disperser’ in terms of flight ability, an ‘income disperser’ in terms of flight performance and an ‘income breeder’ in terms of egg production.

Non-host volatiles (NHV) were tested on antennae of Ips sexdentatus with coupled gas chromatographic-electroantennographic detection (GC-EAD). Significant antennal responses were found to aggregation pheromone components, ipsdienol and amitinol, an attraction inhibitor, verbenone, and non-host bark volatiles extracted from Betula pendula, including trans-conophthorin (tC) and alcohols. The tC, a blend of three green leaf alcohols (C6-alcohols), and a blend of two bark alcohols (C8-alcohols) were tested in combination for their ability to disrupt the attraction of the stenographer bark beetle to pheromone-baited traps, unbaited and pheromone-baited maritime pine logs. The strongest disruptive effect resulted from the addition of the tC combined with the blends of NHV alcohols at high release rate, achieving an 83% reduction in trap catches, 89% reduction of attacks on unbaited pine logs, and 60% on baited logs. It is proposed that the two types of NHV have an additive effect, tC playing a major role in pheromone disruption while the alcohols would interrupt host specific signals. The results suggest that I. sexdentatus uses both bark and green leaf volatiles from non-host tree species in the host selection process. These NHV are promising disruptants, which could be used to prevent stenographer bark beetle attacks on log piles or standing trees in forest. A mixture of conifers and broad-leaved species would also disturb olfactory guided host selection supporting the assumption that more diverse forests are less prone to pest insect outbreaks.

During the last decades, an increasing number of predators were found to use specific prey pheromones as chemical cues. Beyond its ecological relevance, this knowledge has practical applications on insect conservation and pest control. In this study, we present first evidence that two species of the family Dasytidae (Coleoptera)Aplocnemus brevisRosenhauer andA. raymondiSainte-Claire Deville use the sex pheromone of the pine bast scaleMatsucoccus feytaudiDucasse (Hemiptera: Matsucoccidae) as kairomone to locate this prey. The feeding habits and biology ofAplocnemusspecies are practically unknown. In the laboratory, the adults ofAplocnemussp. acceptedM. feytaudiegg masses as food source as well as other diets. Females represented more than 90% ofAplocnemussp. attracted to the pheromone lures. We believe that females use this olfactory cue to locate suitable places for oviposition and that larvae are the predators ofMatsucoccus. This study further demonstrates that the response to the kairomone elicited short prey searching times, about 23% of the individuals appeared less than 12 min after lure exposure, being consistent with the hypothesis of prey specialization. Habitat and geographical distribution predict an ancestral association ofA. breviswithM. feytaudiand ofA. raymondiwithM. pini. Nevertheless, a recent prey shift ofA. raymondito the invasiveM. feytaudiin Corsica is in progress.

International audience; Little attention has been given to the relevance of habitat complementation concept to the population dynamics of insect herbivores. Late instar larvae of the pine processionary moth (PPM) Thaumetopoea pityocampa move in late winter from pine stands, their feeding habitat, to neighbouring habitats where they pupate until next summer. They search for sunny exposed soil which they can find in open areas. We investigated the effect of both forest cover and soil origin, with three matching types (pine stand, broadleaved stand and open area) on the survival of PPM pupae. The microclimatic soil variables which significantly differentiated cover types and soil origins were the maximum temperature and the mean relative humidity in spring, soon after pupation has occurred. A significant effect of the cover type, but not of the soil origin, was detected on the proportion of dead, emerged or diapausing pupae. Open areas were more suitable for pupae survival than forest covers (pine or broadleaved stands), due to warmer and more humid soil conditions. In this study, we provide one of the first examples of habitat complementation for an insect herbivore, as PPM population can benefit from the combination of pine habitats for the feeding of larvae with open habitats for pupation. The presence of broadleaved stands next to pine stands might also represent an ecological trap for PPM pupae, as broadleaved habitats may turn to be less suitable for pupae survival in spring when the apparition of leaves creates cooler conditions.

International audience; The conservation of biodiversity has gained prominence in ecological research for the last decades. Conservation actions require a measure of biodiversity such as species richness, but its assessment is very difficult, even for small areas and therefore the search for surrogates (i.e. indicators) of biodiversity has emerged as an active research topic. We investigated the relationships between butterfly species richness and landscape structure and composition in two pine plantation sites in Southwest France. We assessed the correlation between butterfly species richness and a set of 15 landscape metrics computed for 18 land-uses at 10 different spatial scales. Spatial scales were accounted for by computing landscape metrics for circular buffers with radius ranging from 100 to 1000 m. The joint use of the Partial Least Squares Regression (PLSR) and a stepwise regression procedure revealed strong correlations between butterfly species richness and various landscape metrics in both study sites. The selected landscape metrics differed from one site to another and mostly involved measures of landscape fragmentation. We found a very strong effect of the spatial scale of investigation upon the perception of the landscape–butterfly richness relationship. Our main conclusions are that (i) certain landscape attributes can potentially serve as indicators for butterfly species richness at the landscape scale; (ii) future indicators of biodiversity based on landscape features should consider various spatial scales.