Climate Change Modulates Multitrophic Interactions Between Maize, A Root Herbivore, and Its Enemies

How climate change will modify belowground tritrophic interactions is poorly understood, despite their importance for agricultural productivity. Here, we manipulated the three major abiotic factors associated with climate change (atmospheric CO2, temperature, and soil moisture) and investigated their individual and joint effects on the interaction between maize, the banded cucumber beetle (Diabrotica balteata), and the entomopathogenic nematode (EPN) Heterorhabditis bacteriophora. Changes in individual abiotic parameters had a strong influence on plant biomass, leaf wilting, sugar concentrations, protein levels, and benzoxazinoid contents. Yet, when combined to simulate a predicted climate scenario (Representative Concentration Pathway 8.5, RCP 8.5), their effects mostly counter-balanced each other. Only the sharp negative impact of drought on leaf wilting was not fully compensated. In both current and predicted scenarios, root damage resulted in increased leaf wilting, reduced root biomass, and reconfigured the plant sugar metabolism. Single climatic variables modulated the herbivore performance and survival in an additive manner, although slight interactions were also observed. Increased temperature and CO2 levels both enhanced the performance of the insect, but elevated temperature also decreased its survival. Elevated temperatures and CO2 further directly impeded the EPN infectivity potential, while lower moisture levels improved it through plant- and/or herbivore-mediated changes. In the RCP 8.5 scenario, temperature and CO2 showed interactive effects on EPN infectivity, which was overall decreased by 40%. We conclude that root pest problems may worsen with climate change due to increased herbivore performance and reduced top-down control by biological control agents

Chemical host-seeking cues of entomopathogenic nematodes

Entomopathogenic nematodes (EPNs) are obligate parasites that infect a broad range of insect species. Host-seeking is a crucial step for EPN infection success and survival. Yet, the identity and ecological functions of chemicals involved in host-seeking by EPNs remain overlooked. In this review, we report known CO2, plant-derived and insect-derived cues shaping EPN host-seeking and recognition. Despite species-specific response to environmental cues, we highlight a hierarchical integration of chemicals by EPNs. We further emphasize the impact of EPN selection pressure, age, and experience on their responsiveness to infochemicals. Finally, we feature that EPN chemical ecology can translate into powerful sustainable strategies to control insect herbivores in agriculture

Social network position is a major predictor of ant behavior, microbiota composition, and brain gene expression

The physiology and behavior of social organisms correlate with their social environments. However, because social environments are typically confounded by age and physical environments (i.e., spatial location and associated abiotic factors), these correlations are usually difficult to interpret. For example, associations between an individual’s social environment and its gene expression patterns may result from both factors being driven by age or behavior. Simultaneous measurement of pertinent variables and quantification of the correlations between these variables can indicate whether relationships are direct (and possibly causal) or indirect. Here, we combine demographic and automated behavioral tracking with a multiomic approach to dissect the correlation structure among the social and physical environment, age, behavior, brain gene expression, and microbiota composition in the carpenter ant Camponotus fellah . Variations in physiology and behavior were most strongly correlated with the social environment. Moreover, seemingly strong correlations between brain gene expression and microbiota composition, physical environment, age, and behavior became weak when controlling for the social environment. Consistent with this, a machine learning analysis revealed that from brain gene expression data, an individual’s social environment can be more accurately predicted than any other behavioral metric. These results indicate that social environment is a key regulator of behavior and physiology.La physiologie et le comportement des organismes sociaux sont liés à leurs environnements sociaux. Cependant, les environnements sociaux sont généralement confondus par l'âge et les environnements physiques (c'est-à-dire, la localisation spatiale et les facteurs abiotiques associés), rendant ces corrélations souvent difficiles à interpréter. Par exemple, les associations entre l'environnement social d'un individu et ses patrons d'expression génique peuvent résulter à la fois de l'âge ou du comportement. La mesure simultanée des variables pertinentes et la quantification des corrélations entre ces variables peuvent indiquer si les relations sont directes (et potentiellement causales) ou indirectes. Ici, nous combinons le suivi démographique et comportemental automatisé avec une approche multiomique pour disséquer la structure de corrélation parmi l'environnement social et physique, l'âge, le comportement, l'expression génique cérébrale et la composition de la microbiote chez la fourmi charpentière Camponotus fellah. Les variations dans la physiologie et le comportement étaient les plus fortement corrélées avec l'environnement social. De plus, des corrélations apparemment fortes entre l'expression génique cérébrale et la composition de la microbiote, l'environnement physique, l'âge et le comportement sont devenues faibles lorsque l'on contrôlait pour l'environnement social. En accord avec cela, une analyse d'apprentissage automatique a révélé que, à partir des données d'expression génique cérébrale, l'environnement social d'un individu peut être prédit de manière plus précise que toute autre mesure comportementale. Ces résultats indiquent que l'environnement social est un régulateur clé du comportement et de la physiologie

Targeted treatment of injured nestmates with antimicrobial compounds in an ant society

Abstract Infected wounds pose a major mortality risk in animals. Injuries are common in the ant Megaponera analis, which raids pugnacious prey. Here we show that M. analis can determine when wounds are infected and treat them accordingly. By applying a variety of antimicrobial compounds and proteins secreted from the metapleural gland to infected wounds, workers reduce the mortality of infected individuals by 90%. Chemical analyses showed that wound infection is associated with specific changes in the cuticular hydrocarbon profile, thereby likely allowing nestmates to diagnose the infection state of injured individuals and apply the appropriate antimicrobial treatment. This study demonstrates that M. analis ant societies use antimicrobial compounds produced in the metapleural glands to treat infected wounds and reduce nestmate mortality