REDUCED PETAL SIZE AND COLOR ASSOCIATED WITH TRANSITIONS FROM OUTCROSSING TO SELFING IN CAMISSONIOPSIS CHEIRANTHIFOLIA (ONAGRACEAE)

Floral traits used to attract and reward pollinators should become vestigial during the evolution of self-fertilization from outcrossing due to the reduced fitness benefits of investing in pollinator attraction. However, few traits have been studied, and covariation with outcrossing is rarely evaluated using genetic estimates of the mating system. We examined covariation between petal size and color and genetic estimates of outcrossing among populations of the yellow-flowered, bee-pollinated Camissoniopsis cheiranthifolia that exhibit striking variation in the mating system. We measured brightness, chroma, and hue, using a spectrophotometer, and petal size, using image analysis for flowers sampled in the field from 25 populations across the species' geographic range. Petals were brighter with higher chroma and lower hue (less red) in large-flowered populations than in small-flowered populations. Petal size, brightness, and chroma also correlated positively with the proportion of seeds outcrossed estimated from marker-gene analysis for a subsample of 11 populations. Parallel changes in petal size and color in selfing populations from two climatically different regions plus the maintenance of differences in flower size and color between large-and small-flowered populations when grown in a common glasshouse environment suggests genetic differentiation in these traits associated with mating system evolution.