title: Comparative studies of evolutionary responses to light environments in Arabidopsis.
abstract: In this article, we compare the reaction norms to foliage shade (changes in light quality, spatially fine-grained environmental variation) and photoperiod (day length, spatially coarse-grained environmental variation) in several haplotypes of Arabidopsis thaliana from Scandinavia. We found that both across-environment means and phenotypic plasticities evolved continuously and very rapidly within this group. Both character means and trait plasticities were highly integrated, in part as predicted by the adaptive plasticity hypothesis for response to foliage shade (the so-called shade-avoidance syndrome). We found that a significant but small fraction of the variance in across-treatment trait means and plasticities in response to one environmental factor is explained by variation of the same traits in response to the other factor. Genetic relatedness based on chloroplast DNA sequence variation among haplotypes was not associated with variation in across-treatment character means or their plasticities, suggesting that evolution of these characters has occurred on a local geographic scale via reticulation (outcrossing) among maternal lines rather than by the differential survival of selfing lineages.
authors.affiliation: Department of Botany, University of Tennessee, Knoxville, Tennessee 37996-1100, USA. pigliucci@utk.edu
authors.forename: Massimo
authors.initials: M
authors.lastname: Pigliucci
authors.forename: Heidi
authors.initials: H
authors.lastname: Pollard
authors.forename: Mitchell B
authors.initials: MB
authors.lastname: Cruzan
mesh_terms: D000222:Adaptation, Physiological; D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development* / Q000528:radiation effects*; D005075:Biological Evolution; D018742:DNA, Chloroplast / Q000235:genetics; D004777:Environment; D006239:Haplotypes; D008027:Light; D010641:Phenotype; D017440:Photoperiod; D010802:Phylogeny; D012537:Scandinavian and Nordic Countries
chemical_list: D018742:DNA, Chloroplast