John K Kelly1, Liza M Holeski, H S Arathi. 1. Department of Ecology and Evolutionary Biology, University of Kansas, 1200 Sunnyside Avenue, Lawrence, KS 66045-7534, USA.
Abstract
QUESTION: Does water loss during drought stress represent an important physiological constraint on the evolution of flower size? ORGANISM: A genetically diverse population of Mimulus guttatus (yellow monkeyflower) originally sampled from an alpine meadow in Oregon, USA. METHODS: We grew plants of three different genotypic classes (small, medium, and large flowered) under both well-watered and drought-stress conditions and measured water use efficiency using stable carbon isotopes. RESULTS: There was no difference in water use efficiency among flower size genotypes under well-watered conditions, but the water use efficiency of small-flowered plants was substantially lower than that of medium or large genotypes under drought stress. Whether this paradoxical result is a direct effect of flower size or an indirect (i.e. pleiotropic) effect, the presence of a genetic correlation between floral and physiological traits indicates that selection of one does impact the other.
QUESTION: Does water loss during drought stress represent an important physiological constraint on the evolution of flower size? ORGANISM: A genetically diverse population of Mimulus guttatus (yellow monkeyflower) originally sampled from an alpine meadow in Oregon, USA. METHODS: We grew plants of three different genotypic classes (small, medium, and large flowered) under both well-watered and drought-stress conditions and measured water use efficiency using stable carbon isotopes. RESULTS: There was no difference in water use efficiency among flower size genotypes under well-watered conditions, but the water use efficiency of small-flowered plants was substantially lower than that of medium or large genotypes under drought stress. Whether this paradoxical result is a direct effect of flower size or an indirect (i.e. pleiotropic) effect, the presence of a genetic correlation between floral and physiological traits indicates that selection of one does impact the other.