A herb found in northern Arizona grows better after being eaten by deer
when Ken Paige of the University of Illinois, Urbana, usa , reported a decade ago that scarlet gilia, a delicate red-flowered herb found in the mountains of northern Arizona, produced more seeds when deer nibbled at them, there were few takers. Ecologists were skeptical and were not ready to accept that reproduction of a plant could benefit from being eaten by herbivores.
After studying seeds and pollen production in gilia, Paige now claims that browsing by herbivores enhances the overall reproductive functioning of the plant. His findings are based on experiments in which he trimmed gilia plants with scissors as a substitution for browsing. Paige observedthat the plants regrew to produce more than twice as many flowers and pollen grains per plant than the uncut ones ( New Scientist , Vol 155, No 2096).
To cross-check his finding, Paige pollinated cut and uncut plants with a humming bird and hawkmoth -- natural pollinators of gilia -- by keeping them in the same cage. At the end of the growing season, he sprouted the seeds and used dna identification technique to determine the paternity of 28 offspring plants. The cut plants were responsible for 19 out of 28, the proportion that would come from extra pollen count.
Paige says that this unusual behaviour of the plant suits the conditions in which it exists. The gilia is subjected to intense grazing every summer by migrating herds of deer and elk that move through the mid-elevation habitat of the plant, to higher terrain.
The plants have developed a system of growing a single shoot early in spring and then growing profusely after the herbivores have moved on. This "deer detector" method, as Paige calls it, helps the plants to produce their maximum amount of flowers, seeds, and pollen grains.
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