Chinese Medicinal Plant Tricks Predatory Wasps Into Dispersing Its Seeds By Smelling Like Prey

Chinese scientists have discovered how a plant tricks wasps into carrying its seeds great distances. Photo Credit: adapted from Chen et al. 2017 Figure S1; used with permission from Gao Chen Stemona tuberosa is well known for its use in Chinese traditional medicine, but it's got a much more intriguing claim to fame. It's one of less than a handful of plants known to science that engages in vespicochory—that is, it gets predatory wasps to disperse its seeds. It was a strange enough discovery that Gao Chen and his colleagues at the Chinese Academy of Sciences in Beijing wondered how the plants manage to convince the hornets to haul their offspring around. All it takes is the right scent, the team discovered: parts of the plant smell and taste like the insects the hornets normally hunt. Lots of plants convince wasp relatives—particularly ants—to move their young around. In fact, ant-mediated seed dispersal or mymecochoryhas evolved at least 100 times in flowering plants and is used by more than 11,000 species. And until Chen and his colleagues took a closer look, that's how it was thoughtStemona tuberosa seeds were dispersed, too. But when Chen and his colleagues decided to study the plant in greater detail, they saw wasps carrying away seeds instead. They soon realized the predators "pounce" on the protected seeds of the plant (called diaspores)—as "if they were trying to ‘kill’ them by biting, much like their behavior when attacking prey". Once a wasp rips off a seed, it drags it quite far—an average of over 110 meters away. Often, the helpful hornet eventually stops to rip off most of a fleshy external part called the elasiosome—usually considered the bait for seed-dispersing ants—and takes it with them to their nest (presumably to feed their young). That leaves the diaspore with its seed behind, where ants can discover it and take it to their nests—putting the seeds exactly where they need to be to germinate.