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

Abstract

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.

Morphological, physiological and anatomical traits of plant functional types in temperate grasslands along a large-scale aridity gradient in northeastern China

“…and Medicago sativa L.). These species are representative of the region’s PFTs15, and the five PFTs are the typical plant function types in local vegetation.…”

“…In the long-term, plants develop these strategies through a variety of adaptive traits involving minimization of water loss and maximization of water uptake. Water loss is minimized by changing stomatal traits11, increasing leaf mass per area (LMA), thickening leaf blades12, and enhancing proline and soluble sugar contents in leaf cells to maintain water balance and cell turgor under water scarcity13141516. Meanwhile, water uptake is maximized by increasing investment in vessel number and size in stems and enlarging vessel diameter in leaves1718.…”

A simple procedure for the comparison of covariance matrices

“…The more easily estimated matrix of phenotypic variances and covariances P can be used as a surrogate for G , especially in the case of high heritability morphological characters [1-4]. Comparisons between covariance matrices are carried out in the study of a wide array of evolutionary problems, such as the stability of G in the presence of selection and drift [5-7], the role of genetic constraints on determining evolutionary trajectories in adaptive radiations [8], the response of genetic architecture to environmental heterogeneity [9], the evolution of phenotypic integration [4,10], multi-character phenotypic plasticity [11] and sexual dimorphism [12,13]. …”

Unifying individual differences in personality, predictability, and plasticity: a practical guide

“…Positive correlations might be common, due to shared mechanisms in the maintenance of plasticity. Plasticity that shows phenotypic integration, or modularity, has been of enduring interest to plant scientists (Gianoli & Palacio-Lopez, 2009;Mallitt et al, 2010;Pigliucci, 2002;Schlichting, 1989). Alternatively, a negative correlation in the magnitude of plasticity could reflect trade-offs due to associated costs (DeWitt et al, 1998), while the absence of a correlation suggests the traits have been selected…”