Ecology is full of surprises. And often those surprises have to do with microbes. I’ll write more about microbes in the coming months. I was lucky this week to be able to write about chili peppers and the strange ecology that allowed them to evolve spiciness.
Short version: Josh Tewksbury at the University of Washington, and a team of researchers, found that the spicy substance inside peppers acts as a defense against a fungus. That fungus destroys the seeds inside the peppers. (It turns them black and generally very gross looking.) In climate zones where the fungus grows more readily, the peppers evolved to be spicier. Specifically, they produce more capsaicin. The same chili species in drier zones is not spicy at all.
But what makes it not just interesting, but fascinating, is the three-way relationship between the chili plant, the fungus and a tiny insect. Without all three, the world would be full of bland food.
The insects, as Tewksbury describes them, have mouths shaped like drill bits. They drill into the chili fruit and into the seeds, and eat the nutritious inside of the seeds. They can do a lot of damage, but they don’t destroy all the seeds. However, the holes they drill allow the fungus to get inside the waxy fruit surface and seed surface. By secreting a spicy substance around the seeds, the plant keeps the fungus at bay, just enough to keep the fruit and seeds looking healthy.
As long as the chili peppers look tasty, birds will eat them, as birds are not sensitive to spiciness. And birds are the main distributors of chili pepper seeds.
If you take any of the creatures out of the system, you don’t get spicy habaneros or jalapenos or any of the other peppers we know and love. In fact, all spicy peppers, along with sweet peppers, evolved in the dry forests of Bolivia, Argentina and Paraguay. People bred many varieties from just a few core species. They spread around the world, including to India and Thailand, only post-Columbus.
Wow.
Science and Wonder 