Cambridge, Mass. - November 15, 2011 - Columbine flowers are recognizable by the long, trailing nectar spurs that extend from the bases of their petals, tempting the taste buds of their insect pollinators.
New research at Harvard and the University of California, Santa Barbara (UCSB) helps to explain how columbines have achieved a rapid radiation of approximately 70 species, with flowers apparently tailored to the length of their pollinators' tongues.
Bees, for example, enjoy the short spurs of Aquilegia vulgaris, whereas hawkmoths favor A. longissima, whose spurs can grow to up to 16 centimeters.
According to results published today in the Proceedings of the Royal Society B, the dramatic diversity in the length of the columbines' spurs is the result of one simple change during development: the extent of cell elongation.
"The evolutionary importance of interactions between flowers and pollinators has been recognized for centuries," says co-lead author Sharon Gerbode, a postdoctoral fellow at the Harvard School of Engineering and Applied Sciences (SEAS).
"Charles Darwin, observing orchids, recognized that the extraordinarily long nectar spur on the Angraecum must have evolved in concert with the equally long tongue of the moth that pollinated it, but the exact mechanism for this kind of adaptation has been a matter of speculation."
For more than 60 years, biologists have assumed that the length of columbine spurs was achieved primarily by cell proliferation. The new research reveals that proliferation plays almost no role at all in creating the vast diversity of Aquilegia species currently seen.
In fact, 99 percent of the variation in spur length can be attributed to changes in cell shapespecifically, changing round cells into long ones.
The researchers made more than 13,000 measurements to count the number of cells along the spur, as well as the area and degree of elongation of e
|Contact: Caroline Perry|