Genetic divergence causes parallel evolution of flower color in Chilean Mimulus.

Deciphering the genetic architecture of phenotypic change provides a framework for understanding how evolution proceeds at a genetic level, and paves the way for work at the molecular level. A series of intra- and interspecific crosses were used to investigate the genetic control of recently evolved floral pigmentation phenotypes in a group of closely related Mimulus species from central Chile. An intraspecific polymorphism was found to be controlled by a single Mendelian locus. Differences between species, by contrast, were composed of multiple independent patterning elements, including both Mendelian and polygenic traits. The most striking phenotypic novelty in this group, anthocyanin pigmentation in the petal lobes, has evolved three times independently. The results illustrate how genetically simple modular elements can interact with polygenic or quantitative traits to create complex new phenotypes. The repeated evolution of petal lobe anthocyanins suggests that natural selection may have played a role in the evolution of red coloration in the Chilean Mimulus, and shows that red coloration has been achieved via different genetic pathways in these closely related species.