Plasticity of traits and correlations in two populations of Convolvulus arvensis (Convolvulaceae) differing in environmental heterogeneity

Ecological theory predicts that a generalist strategy should be more favored in changing environments than in stable environments. I tested whether phenotypic plasticity is greater in plants from a temporally heterogeneous habitat than in plants from a more homogeneous habitat. In addition, I evaluated whether the environmental heterogeneity of the original habitat influences the relationship between environmental stress and phenotypic integration, i.e., the degree of correlation among phenotypic traits. The perennial weed Convolvulus arvensis L. was used as a model species. Plants were collected in agrestal (oat field) and ruderal (wasteland) populations located in the same area of central Chile. In situ measurements during the growing season determined that the agrestal habitat was heterogeneous and the ruderal habitat homogeneous for soil moisture, but both habitats were heterogeneous for light intensity. Phenotypic plasticity to light and moisture was evaluated in a common garden, with two light levels (100% and 20% full sunlight) and two moisture treatments (control and low watering). Although the magnitude of phenotypic plasticity to light was very similar in plants coming from the agrestal and ruderal habitats, plastic response to moisture was greater in plants from the agrestal habitat. These results agree with the determination of habitat temporal heterogeneity for light and moisture availability, and hence support the tenet of predominance of a generalist strategy in changing environments. A positive relationship between environmental stress and phenotypic integration was verified. This relationship was stronger in plants from the ruderal habitat. These results contribute to the elucidation of the ecological significance of phenotypic integration in plants.