Researchers identified a surprising evolutionary mechanism that allows carnivorous pitcher plants to capture large "batches" of ants at the same time.
These plants use slippery "pitfall" traps to capture their prey, but scientists were perplexed when they discovered they switched off this mechanism for periods of time, the University of Bristol reported. A research team found the perceived evolutionary disadvantage actually did the plants a vital service.
"The plant's key trapping surface is extremely slippery when wet but not when dry. For up to eight hours during dry days, these traps are 'switched off' and do not capture any of their insect visitors. At first sight, this is puzzling because natural selection should [favor] traps that catch as many insects as possible," said Ulrike Bauer from Bristol's School of Biological Sciences.
The researchers reviewed surveys of wild plants In Borneo, and found the pitcher plants sporadically capture large groups of ants of the same species. The team then conducted experiments in which they artificially kept the surface slippery at all times and found this caused the plants to no longer capture large batches of ants.
"Ants are social insects," Bauer explained. "Individual 'scout' ants search the surroundings of the nest for profitable food sources. When they find a pitcher trap full of sweet nectar, they go back to the colony and recruit many more ant workers. However, a trap that is super-slippery all the time will capture most of these scout ants and cut off its own prey supply."
Switching off the slippery mechanism allowed scout ants to discover the nectar and safely report back to the colony in order to recruit their nest-mates. Later when the pitcher becomes wet agiain it captures those that followed the scout to the potential food source.
"What looks like a disadvantage at first sight, turns out to be a clever strategy to exploit the recruitment behaviour of social insects," the researchers reported.
The findings were published in a recent edition of the Proceedings of the Royal Society B.
