When opposites don't attract.The quirks of two kinds of European corn borers borer, name applied to various animals that are injurious because of their ability to penetrate plant or animal tissues. Among insects, some borers are beetles, e.g., the flatheaded apple-tree borer, a serious pest of many shade and fruit trees; the roundheaded apple-tree borer; and the bronze birch, locust, elm, shot-hole, and poplar borers. Other boring insects are moths that are harmful in the larval stage, e.g. are giving researchers another way to study how a single species might split in two. The classic scenario for forming a new species starts when a geographic barrier, such as a mountain range, emerges and divides a single species. In recent decades, though, biologists have found populations that seem to be splitting even though they could in theory mingle geographically. For instance, two races within a corn borer corn borer or European corn borer European corn borer: see corn borer., common name for the larva of a moth of the family Pyralidae, introduced from S Europe into the Boston area in 1917. The corn borer, Ostrinia nubilalis, has steadily spread southward into the Gulf States and northward and westward across the continent to the Rocky Mts. It also still occurs in most of Europe and parts of Asia. The full-grown larva is about 1 in. (2. species in France live side by side but generally attack different host plants, says Thibaut Malausa of Paul Sabatier University-Toulouse III in France. One race feeds and lays eggs mostly on corn, while the other prefers hops or mugwort 1. any of several plants of the genus Artemisia, particularly A. vulgaris. 2. a preparation of A. vulgaris, used internally for gastrointestinal complaints and as a tonic; also used in homeopathy and traditional Chinese medicine. . The researchers used genetic markers and chemical indicators to measure the tendency of individuals to pick mates like themselves. Called assortative assortative /as·sor·ta·tive/ (ah-sor´tah-tiv) characterized by or pertaining to selection on the basis of likeness or kind. mating, this is a critical factor in maintaining genetic differences among geographically mingled races. At four study sites, mate-seeking borers found a partner within their own race about 95 percent of the time. The researchers note that each race relies on its own pheromone pheromone /pher·o·mone/ (fer´ah-mon) a substance secreted to the outside of the body and perceived (as by smell) by other individuals of the same species, releasing specific behavior in the percipient. pher·o·mone (f to attract mates, but no one yet knows how these pheromone differences arose. The researchers report their findings in the April 8 Science.--S.M. |
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