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Release: Immediate

UI researcher finds wide buffer zones needed to ensure tropical forest diversity

IOWA CITY, Iowa -- Tropical parks and forest preserves may require buffer zones extending more than eight miles beyond their boundaries in order to ensure the survival of their rich diversity of plant and animal life, according to research findings published by a University of Iowa biologist in the Wednesday, Feb. 11 issue of the British journal Nature.

John D. Nason, associate professor in the UI department of biological sciences, bases his conclusion on his study of the pollination patterns of several species of fig trees in the vicinity of Barro Colorado Island, Panama. Figs were chosen for the study because their populations bear fruit year round and are key to the survival of many animal species. Nason says that although their importance in the New World tropics and in Asia is well recognized, the question of how large biological reserves must be to preserve fig populations had never been adequately answered.

Nason found that fig trees, which are pollinated by species-specific wasps, are routinely pollinated at distances of about 3.5 to 8.5 miles between host trees. Because of such wide pollen movement, breeding groups of fig trees can exist over areas as large as 225 square miles, an order of magnitude larger than for any other plant species. Moreover, he found his results likely can be applied to the roughly 350 species of fig trees that share similar pollination systems.

Nason says that fig populations in South Africa and in the Krakatau Islands are currently being studied to test his results, and the need for further information seems clear.

"Information guiding the establishment of reserve areas sufficient for the long-term preservation of fig populations is of vital importance to the management of tropical biodiversity, particularly as large areas of continuous tropical forest become increasingly fragmented by human activities," Nason says. "The results of fig research stress the importance of preserving fig trees, even at low densities and great distances, in surrounding forested areas."

Nason's co-authors are: E. Allen Herre of the Smithsonian Tropical Research Institute, Balboa, Ancon, Republic of Panama; and J.L Hamrick, departments of botany and genetics, University of Georgia, Athens, Georgia.