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BOB HIRSHON (host):
A male-free zone. I’m Bob Hirshon and this is Science Update.
In Nairobi, Kenya, two colorful subspecies of the African Queen butterfly interbreed, producing hybrid offspring of a slightly different color. But none of those babies are male, according to University of Exeter entomologist Richard ffrench-Constant.
RICHARD FFRENCH-CONSTANT (University of Exeter, Cornwall):
Whenever rare male migrants go in to this hybrid zone they do mate endlessly, because obviously they’re vastly outnumbered by the females, but they never produce any males.
Ffrench-Constant says a primitive microbe called spiroplasma selectively kills the males and is passed from mothers to their offspring. His team reports in the Proceedings of the Royal Society B that a single gene controls the color of the butterflies and their susceptibility to the male killer. The researchers think the microbe may be separating the two subspecies and driving their evolution into two non-interbreeding species. I’m Bob Hirshon, for AAAS, the science society.
Story by Susanne Bard