Multigenerational impacts of insecticides on behaviour, life history and fitness in a wild insect

Insects are the most diverse group of animals on Earth, and play vital roles in maintaining ecosystems. As pollinators, nutrient recyclers, natural pest controllers, and ecosystem engineers, they are essential to the health of the environment. However, recent reports highlight significant declines in insect populations, threatening the essential services they provide. The reasons behind these declines are complex, but effects of agricultural pesticides on non-target species have been identified as a potentially major contributor. Research shows that pesticides have sublethal effects on various traits in insects, such as foraging, movement, learning, and lifespan. In response to these findings, the European Union has banned several pesticides. However, our understanding of how these chemicals and their successors affect non-target insects in their natural environments is still limited. Most of what we know comes from lab-based studies, where controlled conditions provide enormous power to detect effects, but fail to capture how insects interact with their environment. This lack of real-world context is a concern because many critical factors, like the presence of predators or changing environmental conditions, aren't accounted for. To address this deficit, we aim to study the effects of pesticide exposure in nature using a unique experimental field system: "WildCrickets". By studying insects in their natural habitat, we can observe how pesticides impact individual fitness through longevity and reproductive success, as well as the traits that contribute to fitness including behavioural and life-history traits. Furthermore, by following successive generations, we can determine whether pesticides only affect exposed individuals or whether impacts can be passed on to offspring. A key focus of our project is how pesticides affect predator avoidance. In labs, predators are absent, but in the wild, being eaten is a major risk factor for most insects. Pesticides may impair insects’ ability to evade predators, which could have a significant effect on their fitness. Similarly, mating behaviours may be disrupted by chemicals affecting reproduction. Another area of focus is how pesticides affect the ability of insects to control their body temperature. For crickets and many other temperate insects, this is particularly important, as they rely on moving between sun and shade to optimise their body temperature. In addition to understanding immediate sublethal effects in their environmental context, another key question is the long-term impact of pesticide exposure on population evolution. For example, if pesticides affect traits related to sexual selection, such as a male’s ability to compete for mates, this may impact the rate at which a population can adapt to changes in its environment. Our research has both ecological and practical implications. By studying the effects of pesticides in the wild, we will address key knowledge gaps and contribute to more accurate environmental risk assessments for pesticides. European authorities have already acknowledged that current pesticide risk assessment methods are outdated. Our findings will help improve these frameworks by identifying where key risks lie. Ultimately, our goal is to use fundamental research in evolutionary ecology to support the development of more sustainable agricultural practices that minimize harm to insect populations.