The plasticity of phenotypic integration in response to light and water availability in the pepper grass, Lepidium bonariense

Organisms that live in a heterogeneous environment face a number of important challenges. On one hand, they require the flexibility to respond to environmental conditions and change their phenotype accordingly. On the other, they are required to be robust in their overall body plan to ensure an integrated, functional organism. Here, we examine the relationship between phenotypic plasticity and integration in the common peppergrass, Lepidium bonariense, by examining the multivariate response of a series of functional traits to a combination of light and water treatments. Lepidium bonariense displayed considerable variation in phenotype in response to water and light availability with the extraction of the first two principal components retaining 85% of the total variation in our data set. Principal component 1 (PC1) largely reflects the negative genetic correlation between specific leaf area and overall plant size, whereas PC2 was typical of a shade-avoidance syndrome displayed by many species of vascular plants. Both PC1 and PC2 exhibited considerable variation among genotypes in phenotypic plasticity in response to the combined effect of light and water availability. Despite complex plasticity in this species, we demonstrate that variation in light and water availability did not significantly influence patterns of functional trait integration, with the genetic variance-covariance matrix remaining stable across environments.