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Genetic Linkage

Bed Bug Orgies and Evolution

Seeking evidence for evolution? Look at bed bugs.

For the past century, the 5-millimeter-long, triangular headed, reddish residents of urban hotel bedrooms have mutated themselves into resistance to any insecticide we can throw at them. Cimex lectularius was nearly vanquished mid-century, when resistance to the chrysanthemum extract pyrethrin led them to resurge to spectacular new numbers. And now that they’re doing so well, their genomes haven’t changed much. Why should they? In genetics, if it ain’t broke, changes won’t persist.

The genetic uniformity that threatens to doom the cheetah and ups the odds of relatives inheriting rare genetic diseases favors the well-adapted bed bugs.

Because bed bugs are so genetically alike, researchers need only peek at a few places in the resilient little beasts’ genomes to deduce how they easily invade mattress seams, box spring crevices, and headboard cracks. Doing so showed that although bed bug populations differ in different regions, probably because we schlep them around in our briefcases and clothing, those within an infested apartment are remarkably alike.

The scenario is clear: a few bed bugs find themselves in a warm, cozy hotel room, and have an orgy. Parent mates with child, sibling with sibling, any bug with any other bug. In some cities, checking bedbugregistry.com is as vital to travelers as checking in for a flight.

Coby Schal and Ed Vargo, entomologists at North Carolina State University, reported results of experiments to track and color-code variants of key genes among bed bugs in hotel rooms and in homes, from Maine to Florida, at the annual meeting of the American Society of Tropical Medicine and Hygiene December 6 in Philadelphia. Their lovely charts clearly reveal spread from floor to floor. Because the selected-for genome keeps the bed bugs so healthy, even in the face of our sprays, they not only persist, but spread. Ditto cockroaches.

That’s evolution – when things work, it slows.
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