Losing one’s touch: Evolution of the touch-sensitive stigma in the Mimulus guttatus species complex

Jannice Friedman, Katherine S. Hart, Meghan C. Den Bakker

Research output: Contribution to journalArticlepeer-review

10 Scopus citations


PREMISE OF THE STUDY: The stigmas of several species are touch sensitive and respond to pressure by closing. Previous research suggests that stigma closure could prevent self pollination within a flower during a pollinator’s visit or enhance male function by increasing pollen export. Both factors could be favored in outcrossers, and neither would be beneficial in selfers. METHODS: We investigated variation in stigma-closing and the duration of closure in annual and perennial populations of the variable species Mimulus guttatus and whether four closely related selfing species (M. cupriphilus, M. laciniatus, M. nasutus, and M. pardalis) have lost their touch sensitivity. We grew plants in a controlled environment and performed experiments with and without the addition of pollen to the stigma. KEY RESULTS: In M. guttatus, the speed of stigma-closing was rapid and unaffected by the deposition of pollen. Populations varied significantly in closing speed, which may reflect their geographic location. For annual populations only, anther–stigma separation significantly affected closing speed. Also, stigmas that closed quickly stayed closed longer, and stigmas that received pollen remained closed longer. Finally, in the selfing species, stigma-closing was more variable; some populations have entirely lost the ability to respond to touch. CONCLUSIONS: We discuss our results in the context of traits that promote outcrossing and traits that are under selection during the evolution of selfing. This is the first characterization of variation in touch responses across multiple populations within a species and the first to demonstrate the loss of touch sensitivity in selfing lineages.

Original languageEnglish (US)
Pages (from-to)335-341
Number of pages7
JournalAmerican Journal of Botany
Issue number2
StatePublished - Feb 2017


  • Herkogamy
  • Mating system
  • Mimulus
  • Outcrossing
  • Phrymaceae
  • Pollination
  • Selfing
  • Touch-sensitive stigma

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Genetics
  • Plant Science


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