Sunday, November 02, 1997
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Death by Slow DegreesDateline: 10/29/97 Because of grave international concerns over rainforest destruction and loss of other shrinking habitats, many countries have begun putting land aside in nature preserves. The Endangered Species Act in the US, for example, has prompted the preservation of such places as Antioch Dunes National Wildlife Refuge and Lake Wales Ridge State Forest. In spite of the many noble attempts to save endangered plant species so far, no one is certain it is adequate. Often the land that is put aside is only a small fraction of a much larger ecosystem. Nowhere is this concern more acute in the botanical world than in the poorly understood relationships between plant and their pollinators. What may appear to be adequate protection for a particular endangered plant, may be inadequate to assure survival of an associated pollinator. Unfortunately, it appears that for many plants, loss of a specialized pollinator may represent a slow death warrant for the plant as well. Bittersweet Agreements From an evolutionary standpoint extreme specialization between a plant species and a specific, dedicated pollinator is a mixed blessing. Extreme specialization does assure that high rates of pollen exchange among individuals in the population can occur. Many orchids of Central and South America are pollinated by euglossine bees. Some euglossine bees are generalists, but others can be adapted to a single species of orchid. The bees act as pollinators because they are rewarded with special scents produced by the flowers. The bees collect these scents and modify them to produce their own sex attractants. The most specialized orchids allow the bee to enter the flower in just a single orientation that causes pollinia (pollen sacs in orchids) to stick to a specific part of the bee's body. When the bee enters another flower of the same species, the orientation of the bee causes the pollinia to be removed and the pollen to contact the s
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