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Identification of two genes causing reinforcement in the Texas wildflower Phlox drummondii


Species formation generates biological diversity and occurs when traits evolve that prevent gene flow between populations. Discerning the number and distribution of genes underlying these traits and, in a few cases, identifying the genes involved, has greatly enhanced our understanding over the past 15 years of species formation (reviewed by Noor and Feder1 and Wolf et al.2). However, this work has almost exclusively focused on traits that restrict gene flow between populations that have evolved as a by-product of genetic divergence between geographically isolated populations. By contrast, little is known about the characteristics of genes associated with reinforcement, the process by which natural selection directly favours restricted gene flow during the formation of species. Here we identify changes in two genes that appear to cause a flower colour change in Phlox drummondii, which previous work has shown contributes to reinforcement. Both changes involve cis-regulatory mutations to genes in the anthocyanin biosynthetic pathway (ABP). Because one change is recessive whereas the other is dominant, hybrid offspring produce an intermediate flower colour that is visited less by pollinators, and is presumably maladaptive. Thus genetic change selected to increase prezygotic isolation also appears to result in increased postzygotic isolation.

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Figure 1: Flower colour phenotypes in F 2 individuals.
Figure 2: Results of expression experiments on the hue locus ( F3′5′h).
Figure 3: Results of expression experiments of the intensity locus ( R2R3-Myb).

Accession codes

Primary accessions


Data deposits

The DNA sequences reported here are deposited in GenBank under accession numbers HQ127319–HQ127344 and HQ323688–HQ323691.


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We thank D. Des Marais, J. Tung, S. Johnsen and T. Juenger for technical advice, D. Levin for assistance in locating natural populations, and M. Noor for comments on the manuscript. This work was supported by a National Science Foundation grant to M.D.R. and a National Science Foundation Doctoral Dissertation Research Improvement Grant to R.H. R.H. was supported in part by the National Science Foundation Graduate Research Fellowship Program.

Author information




R.H. and M.D.R. designed the project; R.H. performed the experiments and the analyses; R.H. and M.D.R. wrote the paper.

Corresponding authors

Correspondence to Robin Hopkins or Mark D. Rausher.

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The authors declare no competing financial interests.

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Hopkins, R., Rausher, M. Identification of two genes causing reinforcement in the Texas wildflower Phlox drummondii. Nature 469, 411–414 (2011).

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