[The following is an exact transcript of this podcast.]
Some peppers have a mild, fresh flavor. But others burn your lips and leave a lingering, numbing kick. If you enjoy that tingling thrill, you might want to say thanks. But not to the peppers themselves—to bugs. Peppers are tasty so they’ll be eaten and have their seeds dispersed. But the snacker has to be the right creature—which the peppers need to be birds. Some insects also like to munch peppers, and they may puncture the skin. The wound leaves an opening for a microbial fungus. The fungus wriggles inside and snacks on the seeds, destroying them.
Researchers from the U.S. and Bolivia tested whether a pepper’s heat offers it protection. They published August 11th in the Proceedings of the National Academy of Sciences. First, they collected chilies from seven populations of the same pepper species over a thousand-mile area. Then they counted insect-induced scars and tested pepper heat. In regions with lots of insects, and a greater risk of death by microbe, plants tended to be much hotter. And the hot chemicals, called capsaicinonids, slow microbial growth. Birds can’t sense capsaicin. So the hot peppers kill bugs, and still attract birds. And many humans, too.