SMITHSONIAN MAGAZINE - Some tomatoes growing on the Galápagos Islands appear to be going back in time by producing the same toxins their ancestors did millions of years ago.
Scientists describe this development—a controversial process known as “reverse evolution”—in a June 18 paper published in the journal Nature Communications.
Tomatoes are nightshades, a group of plants that also includes eggplants, potatoes and peppers. Nightshades, also known as Solanaceae, produce bitter compounds called alkaloids, which help fend off hungry bugs, animals and fungi.
When plants produce alkaloids in high concentrations, they can sicken the humans who eat them. To better understand alkaloid synthesis, researchers traveled to the Galápagos Islands, the volcanic chain roughly 600 miles off the coast of mainland Ecuador made famous by British naturalist Charles Darwin.
They gathered and studied more than 30 wild tomato plants growing in different places on various islands. The Galápagos tomatoes are the descendents of plants from South America that were probably carried to the archipelago by birds.
The team’s analyses revealed that the tomatoes growing on the eastern islands were behaving as expected, by producing alkaloids that are similar to those found in modern, cultivated varieties. But those growing on the western islands, they found, were creating alkaloids that were more closely related to those produced by eggplants millions of years ago.
Researchers suspect the environment may be responsible for the plants’ unexpected return to ancestral alkaloids. The western islands are much younger than the eastern islands, so the soil is less developed and the landscape is more barren.
To survive in these harsh conditions, perhaps it was advantageous for the tomato plants to revert back to older alkaloids, the researchers posit. “The plants may be responding to an environment that more closely resembles what their ancestors faced,” says lead author Adam Jozwiak, a biochemist at the University of California, Riverside, to BBC Wildlife’s Beki Hooper.