|MadSci Network: Botany|
Sweet gum (Liquidambar styraciflua) seeds have wings, as you indicated, so are mainly dispersed by wind. Ninety-six percent of the seeds usually fall within 61 meters of the tree with the record for dispersal at 183 meters. The sweetgum fruit is a multiple fruit consisting of many capsules. A possible "advantage" of that is that many seeds are produced in one structure. Multiple fruits are produced when fruits produced by many separate flowers grow together. Multiple fruits also occur in pineapple, mulberry, figs and Osage orange. The sweet gum fruits stay on the tree most of the winter so they may act primarily as "launching platforms" for the seeds. It is perhaps analagous to the cone of some pine trees, which also have winged seeds dispersed mainly by wind. I agree that it seems unlikely that the sweetgum fruit is adapted for clinging to fur. Who advocates that theory? There are some (Barlow and Martin 2002, Barlow 2001) who believe that several native American trees have adaptations to large herbivorous mammals that are now extinct. However, I don't believe sweet gum was one of their examples. They usually mention the fruit of honey locust, Kentucky coffee tree and Osage orange. References Sweetgum (Liquidambar styraciflua) U.S. Department of Agriculture, Forest Service. 1965. Silvics of forest trees of the United States. H. A. Fowells, comp. U.S. Department of Agriculture, Agriculture Handbook 271. Washington, DC. Unusual Fruits Called Capsules Multiple Fruits Barlow, Connie and Paul Martin, 2002. The Ghosts of Evolution: Nonsensical Fruit, Missing Partners, and Other Ecological Anachronisms. Basic Books Barlow, C. 2001. Ghost Stories From the Ice Age - methods of seed dispersal that date back to Ice Age Natural History. (Sept.)
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