In the grand scheme of strategies to deter predators, sticky columbine takes a rather medieval approach, Sandhya Sekar reports for Science — researchers think it lures innocent bugs to their deaths, then decorates itself with their bodies as “payment” for spiders who attack the plant’s would-be predators.
New research suggests that the sticky leaves and stems of Aquilegia eximia bring a slow death to harmless bugs like beetles and dragonflies, Sekar explains. The dead bodies then serve to attract spiders, which eat the adolescent moth caterpillars (Heliothis phloxiphaga) that threaten the plants’ buds and flowers. The spiders have evolved resistance to the sticky stems and indirectly protect the plant from one of its main predators, writes Sekar.
Plenty of plants, like columbine, have hairy stems covered with sticky droplets of goo where bugs gets stuck and die. Entomologists call them “tourist traps,” notes Elizabeth Preston for Discover. But it’s always been unclear whether the presence of all those bugs is part of the plants’ master plan or more of a coincidence.
To settle the debate, a team of biologists set up some traps with serpentine columbine stalks and some without. Traps with columbine bait snared 21 percent more beetles, dragonflies and other insects. The team also played around with removing the dead bodies from plants in a California reserve. Plants with lower dead body counts had fewer spiders and twice as much caterpillar damage. The team’s results were published in the July issue of Ecology.
The work provides strong evidence that the plants kill the bugs as a kind of payment to spiders, which then serve as their anti-predator muscle. It’s a roundabout system, but it seems to work — and given the prevalence of plants with sticky stems, it might even be pretty common. Just think of it as the plant world’s version of The Bodyguard.