Deception isn’t limited to animals; plants also evolve ways to trick pollinators,enemies,and seed dispersers. Researchers have recently discovered trickery in a climbing vine, the black-bulb yam (Dioscorea melanophyma), which produces fake berries to help spread its seeds, as reported January 12 in the Proceedings of the National academy of Sciences. (https://www.pnas.org/cgi/doi/10.1073/pnas.2528094123)
The discovery “feels refreshingly new,” says Kenji Suetsugu, an evolutionary ecologist at Kobe University in Japan, who wasn’t involved in the study. These yams have lost sexual reproduction and rely on cloning. Plants that clone typically use detachable buds called bulbils, which sprout near the parent plant. However, by transforming these buds into berry-like structures eaten by birds, the yam can spread its seeds over wider distances, protecting against local environmental changes. “It’s a clever evolutionary workaround,” Suetsugu says.
Gao chen, an ecological biologist at the Kunming Institute of Botany, Chinese Academy of Sciences, and his team initially mistook the bulbils for berries while collecting seeds in Southwest China in 2019. Finding no seeds inside, Chen realized, “They can cheat me, then, I think they can cheat birds.”
Bulbils are usually pale, but these are black and shiny, mimicking berries. chen’s team compared the appearance of the yam’s bulbils to 15 nearby berry species, finding them indistinguishable. Three years of camera trap data showed 22 bird species visiting the bulbils, with some consuming them.
In the lab, Chen found the brown-breasted bulbul (Pycnonotus xanthorrhous) generally prefers berries, but will eat the yam’s bulbils when berries are scarce.
