WP2: Effects of pesticides on life history and burrowing activity variation
Rationale: Estimating individual variation in life-history traits is an essential step for calibrating plausible eco-evolutionary models in our final WP. Here we will estimate the repeatability of life-history traits and burrowing behaviors. Because individual differences occur partially due to additive genetic differences among individuals, the repeatability of each trait can serve as the upper-bound for heritability for the modelling approach in WP4. Regressing a fitness proxy against phenotypes allows to compare the intensity and shape of selection under different exposure conditions.
Approach: We will select four pesticide mixture doses ranging from no effect on any of the considered traits to strong effects on all or most traits according to the results of WP1. We will expose a cohort of earthworms over the majority of their life-cycle and track their phenotypes individually in each exposure conditions. We will measure individual cocoon production and track cocoon hatching success to estimate the lifetime reproductive success of individuals. These data will serve to calibrate a hierarchical bioenergetic model accounting for individual variation in life-history and behavior and in ecotoxicological parameters (scaled damage and No Effect Concentration). Next, we will estimate selection gradients by regressing lifetime reproductive success as a fitness proxy against growth, reproduction and burrowing activity data. This WP will allow to estimate the strength and shape of selection acting on individual phenotypes, a key step necessary to predict the evolutionary outcomes of pesticide exposure.
