Ecosystem feedbacks contribute to geographic variation in plant-soil eco-evolutionary dynamics across a fertility gradient

Plant species that occur in different soil nutrient environments often vary in plant functional traits that affect soil nutrient cycling, creating positive feedbacks that reinforce nutrient availability. Variation in such nutrient feedbacks could affect plant fitness, but few studies have explored the eco-evolutionary dynamics of within-species nutrient feedbacks, and the role that soil communities may play in mediating plant evolutionary responses. We investigated whether a widespread Populus species regulates soil fertility, resulting in positive nutrient feedbacks that influence population divergence. Here, we combined field observations, a reciprocal transplant experiment, and soil community sequencing to test how nutrient feedbacks might facilitate plant adaptation to soil environments.