Chemical mediation and niche partitioning in non-pollinating fig-wasp communities

1. The parasitic chalcidoid wasps associated with the species-specific and obligatory pollination mutualisms between Ficus spp. and their agaonid wasp pollinators provide a good model to study the functional organization of communities. 2. However, communities of non-pollinating fig wasps (NPFWs) remain little characterized, and their functioning and evolutionary dynamics are still poorly understood. 3. We studied the communities of NPFWs associated with the monoecious F. racemosa and the dioecious F. hispida. Associated with these two fig species are a total of seven wasp species belonging to three genera. These species present contrasts in life history traits and in timing of oviposition. The species studied are thus broadly representative of the communities of NPFWs associated specifically with fig-pollinator mutualisms. 4. In our study systems, there is temporal segregation of oviposition time among members of NPFW communities.5.We tested the role of volatile chemicals in the attraction of NPFWs associated with these two fig species, and tried to determine if chemical mediation can explain the organization of the communities. 6. We conducted odour choice tests using a Y-tube olfactometer. All the NPFWs studied were shown to use volatile chemicals produced by the fig to locate their host. Furthermore, the signals used by each species depended on the phenological stage of the fig they exploit. 7. Results demonstrated that the pattern of oviposition results from the utilization of volatile signals produced by figs that vary in their composition at different stages of fig development. Thus, chemical mediation allows resource partitioning in the NPFW communities associated with fig-pollinator mutualisms, and suggests hypotheses to explain coexistence in other parasite communities

Effets de l’ozone sur les interactions entre plantes et pollinisateurs: Détermination des valeurs seuils d’exposition à l’ozone pour la résilience de la communication chimique plantes-insectes

National audienceLes activités humaines représentent une réelle menace pour la pollinisation et le fonctionnement des écosystèmes qu’elle représente. De nombreux travaux ont montré qu’une exposition à l’ozone pouvait avoir des effets nocifs sur les populations humaines et sur la physiologie des plantes. L’objectif du projet ExpOz est de comparer l’effet de plusieurs niveaux d’exposition à l’ozone sur la communication chimique plantes-pollinisateurs. Deux types d’interactions seront étudiées : 1.L’interaction très spécifique entre le figuier cultivé (Ficus carica) et sa guêpe pollinisatrice (Blastophaga psenes) / 2.L’interaction généraliste entre la lavande (Lavandula angustifolia) et l’abeille domestique (Apis mellifera)

Médiation chimique et structuration des communautés d'hyménoptères parasites du mutualisme figuier / pollinisateur

MONTPELLIER-BU Sciences (341722106) / SudocSudocFranceF

Ozone Induces Distress Behaviors in Fig Wasps with a Reduced Chance of Recovery

International audienceAmong anthropogenic environmental risks, air pollution has the potential to impact animal and plant physiology, as well as their interactions and the long-term survival of populations, which could threaten the functioning of ecosystems. What is especially alarming is that the concentration of tropospheric ozone (O3) has dramatically increased since pre-industrial times. However, the direct effects of O3 on the behavior of pollinators themselves have not been investigated so far even though insect behavior is key to their ecological interactions, which underpin the stability of ecological networks responsible for species biodiversity in ecosystems. In this study, we aim to determine the potential effects of O3 episodes at different field-realistic concentrations (0, 40, 80, 120, and 200 ppb for 60 min) on the behavior of the fig wasp Blastophaga psenes by monitoring exposed individuals hourly for 5 h after exposure. We found that ozone episodes induced major changes in insect behavior, which were already significant at 80 ppb with individuals displaying abnormal motility. The tracking over time clearly showed that exposed individuals might only have a reduced chance of recovery, with a decreasing proportion of active fig wasps despite the cessation of an O3 episode. These findings illustrate that O3 episodes can affect pollinator behavior, which may have detrimental implications for pollination systems. It is, therefore, of importance to assess the effects of O3 on insect behavior in order to predict how it could modify ecological interactions and species biodiversity in ecosystems

Ecologie chimique : une science intégrative et expérimentale

National audienc

Chemical Ecology: An Integrative and Experimental Science

International audienc

Un réseau trophique complexe : le cas des figuiers

International audienc

Specificity of pollinators between syntopic species of the genus Ceropegia (Apocynaceae) sharing the same pollination syndrome

International audienceObjective Flowers in the genus Ceropegia L. (Apocynaceae) do not reward pollinators: pollination is based on deceit. Inside the flower, pollen grains are grouped within five pollinia, limiting transfer opportunities. In case of syntopy with species sharing the same pollination syndrome, the risk of losing its pollinia inside another species should induce a selection pressure on pollinator specificity. Method We collected data on basic pollination aspects of four Ceropegia species occurring syntopically in Thailand, analysed floral scent by gas chromatography linked to mass spectrometry (GC/MS), and determined compounds responsible for pollinator attraction in bioassays. Results All pollinators found in the flowers were Diptera from Milichiidae and Chloropidae families, known as kleptoparasites. The floral scents and the scent of a true bug found on site-supposed to be the model mimicked by the flowers-belonged to the same family. This suggests a kleptomyiophilous syndrome: the flower attracts Diptera feeding on the hemolymph of insects captured by arthropod predators. The four plant species showed clearly distinct pollinator communities and floral scents, yet the pollinator attraction with synthetic odors was less specific. Conclusion The pollinator specificity in a syntopic context was confirmed, and implied, at least in part, the floral scents

Acute ozone exposure impairs detection of floral odor, learning, and memory of honey bees, through olfactory generalization

International audienc

An overlooked syndrome of deceptive pollination: Mimicry of food sources for attracting females of anautogenous flies

International audienceTraditionally recognized pollination syndromes are o en too broadly defi ned to represent the diversity of plantpollinator interactions, particularly in plants that deceptively attract insects by mimicking resources they seek. Within such interactions, we document a distinct but previously ill-defi ned deceptive pollination strategy in which plants exploit the protein-seeking behavior of females of anautogenous Diptera by olfactorily mimicking their insect prey. We show that this strategy characterizes at least 97 plant species from seven families, pollinated by females of three dipteran families, Ceratopogonidae, Chloropidae and Milichiidae. Comparison of fl oral odours based on compound identity and structural similarity revealed fl oral traits that characterize a hitherto undescribed pollination syndrome. Interestingly, related plants of three of these families emit a diff erent set of fl oral volatiles to attract fl ies of other families in brood-site mimicry pollination systems. Our fi ndings open new avenues, from both methodological and conceptual perspectives, for understanding the evolution of specialized pollination systems