Reaction norms of Arabidopsis. IV. Relationships between plasticity and fitness

Abstract

The study of the association between fitness and reaction norms is of primary importance given the hypothesized role for phenotypic plasticity in shaping evolutionary patterns: in microevolution, as one mechanism for maintaining genetic variation, and in macroevolution, as a means of generating phenotypic novelties. In a glasshouse experiment, we investigated variation in reaction norms to nutrient availability in populations of Arabidopsis thaliana, and the relationship between this variation and reproductive fitness. We found evidence for acrosstreatment directional selection on the means for leaf number, flowering time, plant height, branching and growth rate; across-treatment stabilizing selection was detected for growth rate; and across-treatment disruptive selection was significant for leaf number. We also uncovered selection on the plasticity of some traits: directional for the plasticity of branching, and stabilizing for the plasticity of both branching and growth rate. When the two environments were considered separately, directional selection for height was detected under low nutrients; under high nutrients, we found evidence for directional selection on leaf number and height, and for disruptive selection on flowering time. The genetic correlation between a trait's expression in one environment and its expression in the alternate environment was positive and highly significant only for flowering time and growth rate. A principal components analysis revealed possible constraints on future selection responses, because of correlations among character means and among character plasticities.

The effect of water availability on plastic responses and biomass allocation in early growth traits of Pinus radiata D. Don

“…For the plasticity analysis the position of each population in the space defined by its mean phenotype under the water stress treatment (on the x-axis) and under the well-watered treatment (on the y-axis) was represented graphically following Pigliucci and Schlichting (1996). This way, each family is represented by a single point and, if the two axes are in the same scale, the main diagonal represents the line of null phenotypic change, that corresponds to a flat reaction norm and the tangent (slope) of the angle α, formed between the line connecting each point to the origin and the x-axis can be interpreted as an index quantifying phenotypic change.…”

Divergence among species and populations of Mediterranean pines in biomass allocation of seedlings grown under two watering regimes

“…Besides plotting standard reaction norms, we represented graphically the position of each population in the space defined by its mean phenotype under the water stress treatment (on the x-axis) and under the non-stress treatment (on the y-axis) following Pigliucci and Schlichting [31]. This way, each population is represented by a single point and, if the two axes are in the same scale, the main diagonal represents the line of null phenotypic change, that corresponds to a flat reaction norm and the tangent (slope) of the angle α, formed between the line connecting each point to the origin and the x-axis can be interpreted as an index quantifying phenotypic change.…”

Expansive Phenotypic Landscape of Botrytis cinerea Shows Differential Contribution of Genetic Diversity and Plasticity

“…For example, Arabidopsis thaliana senses changes in nutrient stress and light intensity and, then, utilizes regulatory machinery to alter their phenotype in response. This process is largely driven by environmental inputs rather than natural genetic difference among individuals (Pigliucci and Byrd 1998;Pigliucci and Kolodynska 2001;Pigliucci and Schlichting 1996). In addition, the soil fungus and facultative epiphyte Aureobasidium pullulans demonstrates a variety of genetically independent morphological traits in response to differences in nutrient source and temperature (Slepecky and Starmer 2009).…”