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.
Description
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