Soil biodiversity is an important reservoir of ecosystem services and is threatened by the wide-scale use of pesticides. Evolution plays a central role in how populations persist because ecological change and evolutionary processes interact in eco-evolutionary feedbacks. These feedbacks can decrease extinction risk by allowing rapid adaptation to environmental stressors but depend on the population density and its genetic makeup. Despite evidence that soil fauna can adapt to pesticide exposure, key questions on the speed at which adaptation occurs and the costs for ecosystem functions remain unanswered. EEWORM will investigate eco-evolutionary dynamics in populations of the earthworm Aporrectodea caliginosa, a major soil engineer in agricultural systems, exposed to a pesticide mixture representative of French agricultural soils. In WP1, I will calibrate a toxicokinetic-toxicodynamic model allowing to predict the outcome of a mixture of epoxiconazole and imidacloprid - two dominant pesticides in agricultural soils - on earthworm growth, reproduction and activity and on organic carbon mineralization. In WP2, I will measure individual differences in growth reproduction and burrowing activity by following a cohort of earthworms over their lifecycle. Individuals will be split in four dose combinations ranging from low to strong effect on all traits based on the data from WP1. This will allow to adjust the TKTD model to account for individual differences in life-history traits and in sensitivity to pesticide mixture. Using lifetime reproductive success as a proxy for fitness will allow to estimate the shape and intensity of selection for all dose combinations. WP3 will test whether tolerance to pesticide exposure may also occur through transgenerational plasticity by splitting offspring from the F0 population from WP2 into exposed and control group. This WP will test different scenarios by which transgenerational plasticity may occur, either by preventing offspring from recovering from parental exposure or leading to habituation or sensitization to pesticide stress. The combined data from WP2 and 3 will therefore allow to contrast the relative influence of selection induced by pesticide exposure and transgenerational plasticity on the expression of life-history and behavioral traits. In WP4, I will use the gathered data to build an individual based model. This model will allow to predict the outcomes of pesticide exposure under field-realistic scenarios on earthworm population dynamics and derive its consequences on carbon mineralization. By combining novel experimental procedures to estimate the evolutionary impacts of pesticides on individual differences in life-history and behavior with advanced modelling approaches, EEWORM will answer a pressing environmental issue: How fast can a key soil engineer adapt to pesticide mixtures and at what cost for soil functions? This project is a unique opportunity for me to lead novel research in evolutionary ecotoxicology as a newly-recruited scientist at INRAE.