Reaction Norms of Arabidopsis. I.

REACTION NORMS OF Arabidopsis. I. PLASTICITY OF CHARACTERS AND CORRELATIONS ACROSS WATER, NUTRIENT AND LIGHT GRADIENTS

Massimo Pigliucci*, Jeannette Whitton, Carl D. Schlichting

Department of Ecology and Evolutionary Biology
University of Connecticut
Storrs
CT 06269
USA

* Author for correspondence. Current address: Ecology and Evolutionary Biology, Box G-W, Brown University, Providence, RI 02912 (pigliucc@brownvm.brown.edu)

Journal of Evolutionary Biology, in press

The univariate and multivariate study of variation for phenotypic plasticity (i.e., the ability of a genotype to produce different phenotypes in response to distinct environments) is central to providing a clear understanding of hypotheses about the genetic control and evolution of reaction norms in natural populations. Arabidopsis thaliana is an ideal organism for the study of Genotype x Environment interactions (i.e., genetic variation for plasticity), because of the ease with which it can be grown in large numbers and due to the amount of information already available on its genetics, physiology and developmental biology. In this paper, we report on the plasticity, genetic variation and GxE interactions of four populations of A. thaliana in response to three environmental gradients (water, light and nutrients), each characterized by four levels of the controlled parameter. We measured nine traits and obtained their reaction norms. Path analysis was used to study the plasticity of character correlations. We found a tendency for A. thaliana reaction norms to be linear (either flat, i.e.,no plasticity, or with a significant slope), in accordance with previous studies. We detected substantial amounts of genetic variation for plasticity in the light and nutrient gradients, but not in the water gradient. Dramatic restructuring of character correlations was induced by changes in environmental conditions, although some paths tended to be stable irrespective of the environment, thereby suggesting some degree of canalization.

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