Phenotypic plasticity is broadly adaptive across an elevation gradient in the Cutleaf Monkeyflower

Phenotypic plasticity is a key mechanism by which organisms can cope with environmental heterogeneity, but its evolutionary consequences depend on how plastic responses align with the broader adaptive landscape.We tested whether plasticity in leaf shape alongside other traits is associated with differential fitness across an elevational gradient in Mimulus laciniatus, an annual wildflower endemic to montane California. Using a reciprocal transplant experiment and recombinant inbred lines (RILs) previously phenotyped for plasticity in controlled conditions, we measured variation in survival and fecundity in native low- and high-elevation habitats.Based on previous work, we expected to find selection against leaf shape plasticity at low-elevation and selection for leaf shape plasticity in the high-elevation direction (increased leaf lobing under long-day conditions) at high-elevation. Interestingly, we found that RIL genotypes exhibiting high-elevation plasticity had the greatest survival to seed production at high-elevations, but that low-elevation plasticity (increased leaf lobing under short-day conditions) was associated with greater fecundity in both elevations. RILs with high-elevation plasticity also outperformed non-plastic genotypes at high-elevation.This pattern suggests that plasticity is broadly beneficial across a species' geographic range even if local variation in the direction of plasticity is not always adaptive.