Jan 20, 2012 - Claremont, Calif. -

Sharon Gerbode

Hawkmoth pollinator visiting an Aquilegia [Columbine] flower. (Credit: S. A. Hodges)

An interdisciplinary paper co-authored by Sharon Gerbode, Harvey Mudd College’s newest assistant professor of physics, was recently published in a prominent British biological research journal.

“Evolution of spur-length diversity in Aquilegia petals is achieved solely through cell-shape anisotropy,” appeared November 15 in the online issue of Proceedings of the Royal Society B. The paper outlines research about the evolution of the Columbine flower, which Gerbode performed while a postdoctoral fellow at the Harvard School of Engineering and Applied Sciences.

Her team discovered that the rapid radiation of about 70 Columbine species—each with spurs specifically suited for its pollinator—could be traced to a single change during development: the extent of cell elongation.

By counting the number of cells along the spurs and measuring the degree of elongation of each cell, they determined that 99 percent of the variation in flower spur length could be attributed to cell shape changes—from round to elongated.

“Often compared with Darwin's finches, [Columbine] petal spurs are long, tubular pockets that are matched to the size and shape of specialized pollinator tongues or beaks,” Gerbode said. “For the past six decades it has been assumed that these elongated petals form via continued cell divisions localized at the tip of the spur. Our paper dispels this widely accepted myth and uncovers the true mechanism for the dramatic diversity in petal spur shape.”

The research findings are expected to direct future genetic investigations of floral organs in association with pollinators, she said.

View the paper here.

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