Figure 2.

Shifts in root traits in response to belowground enemy release. In (A), the alien genotype should change its root traits to increase resource uptake in the alien range soil, compared to native range soil (red, solid line). Without evolution, native genotypes would be expected to respond in a similar manner (black). If enemy release resulted in evolution of root traits reflecting high‐resource uptake, then root traits of the alien genotype will not respond to the native range soil (red, dashed line). In (B) the fitness consequences are that, for ecological shifts in root traits, fitness should be higher for alien (and theoretically for native) genotypes in the alien range soil. If root traits evolved in response to soil‐enemy release, the root traits of alien genotypes should be better adapted to and therefore have higher fitness in alien range soils than in natives, but in the enemy‐bearing soil of the native range, alien genotypes would be maladapted (red dashed line) compared to native genotypes. Ethical considerations may prevent a fully reciprocal design, with native range genotypes in alien range soils omitted (*). However, disentangling ecological and evolutionary responses of root traits to belowground enemy release should still be feasible using the remaining genotype–soil combinations.