Pollinator-Mediated Selection on Flower Color Allele Drives Reinforcement

Abstract

The Constant Pollinator In ecology, reinforcement is the process by which species prevent hybridization and maintain species boundaries, but the underlying genetic mechanisms are unclear. Hopkins and Rausher (p. 1090 , published online 2 February) examined reinforcement between two species of a wild flowering plant called Phlox that show incomplete hybrid sterility. Down-regulation of a flavonoid gene produces red flowers and operates in concert with a color intensity locus to adjust flower color and tone. A distinct geography of flower color has emerged in which it appears that dark coloration causes less hybridization between the species because the butterfly pollinators tend to favor light-blue flower color variants. If pollinators visit flowers with similar phenotypes more frequently than flowers with dissimilar phenotypes, this will decrease gene flow between the unlike flowers.