Linear mixed-effects models to test for local adaptation within regions (Experiment 2).

Analyses were performed by inspecting the effects of the fixed variables geographic distance and region on estimated mean net soil biota effect. Geographic distance denotes the distance between the population of the plant and the soil inoculum. Models were constructed in two ways: A) from the perspective of plant populations growing in increasingly distant soil populations, by including plant population as a random effect, and B) from the perspective of soil populations in which plants from increasingly distant populations were grown, by including soil population as a random effect. P values≤0.01 are marked in bold.