Many of an organism's traits are influenced by cues from the organism's environment. These features are known as phenotypically plastic traits and are important in allowing an organism to cope with unpredictable environments. But what are the genetic mechanisms underlying these traits? National Science Foundation-funded researchers studied phenotypically plastic traits in pea aphids and uncovered, for the first time, genes that influence whether aphids produce wingless or winged offspring in response to their environment. Pea aphids are insects that reproduce rapidly and typically give birth to offspring that do not have wings. As many gardeners know, aphids can quickly overwhelm and kill the host plants on which they live and feed. When an environment becomes too crowded with other aphids, the females begin producing offspring that have wings, rather than the typical wingless offspring. The winged offspring can then fly to and colonize new, less-crowded plants. The researchers used techniques from evolutionary genetics and molecular biology to identify genes that determine the degree to which aphids respond to crowding. Surprisingly, the genes they uncovered are from a virus that then became incorporated into the aphid genome. The virus, which is from a group of insect viruses called densoviruses, causes its host to produce offspring with wings. Researchers believe the virus does this in order to facilitate its own dispersal.
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