Will climate change affect insect pheromonal communication?

Abstract

Understanding how climate change will affect species interactions is a challenge for all branches of ecology. We have only limited understanding of how increasing temperature and atmospheric CO 2 and O 3 levels will affect pheromonemediated communication among insects. Based on the existing literature, we suggest that the entire process of pheromonal communication, from production to behavioural response, is likely to be impacted by increases in temperature and modifications to atmospheric CO 2 and O 3 levels. We argue that insect species relying on long-range chemical signals will be most impacted, because these signals will likely suffer from longer exposure to oxidative gases during dispersal. We provide future directions for research programmes investigating the consequences of climate change on insect pheromonal communication. IntroductionSince the 19 th century, the atmospheric concentration of greenhouse gases, particularly carbon dioxide (CO 2 ), have drastically increased causing changes to environmental parameters at a global scale, including temperature [1]. Recent studies now highlight the impact of such modifications on the whole dynamics of life [2]. Through cascade effects, entire ecosystems are being disturbed, impacting the population dynamics of inhabiting species and altering the ways that they interact with one another. This phenomenon has been well documented for insect-plant interactions mediated by plant secondary metabolites [3,4 ]. [12]. Although these insects can perceive a wide range of pheromone components, the activation of neurons in their macroglomerular complexes, and the elicitation of relevant behavioural responses, is combinatorial: it will happen only when the right combination and ratio of components is perceived at the same time [6].Developmental temperature has a strong influence on adult life history, morphology, and physiology. Furthermore, in some species, pheromone production and availability is dependent on larval, pupation, and/or adult developmental conditions [8,13,14], hence the effect of abiotic parameters on all the insect life stages is important. In the male beewolf, Philanthus triangulum, an increase of 5 8C in the larval rearing temperature led adult males to produce more pheromonal secretions [13]. Moreover, warmer rearing conditions led to higher relative amounts of compounds with high molecular weight. As a consequence, a shift in temperature could weaken intraspecific relationships of these insect species by reducing the efficiency (i.e. specificity, activity, timing of production, etc.) of their chemical communication.Increasing atmospheric CO 2 concentrations [1] could also affect the biosynthesis of insect pheromones. Changes in CO 2 concentrations affect plant biochemistry, including the synthesis of secondary metabolites [4 ]. Since some phytophagous insect species produce their pheromone components based on precursors taken from their host plant, we hypothesise that phytophagous insects could be among the most vulnerable to changes in atmospheric ...

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