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.