Pitcher plants are several different carnivorous plants that have evolved modified leaves known as a pitfall traps – a prey-trapping mechanism featuring a deep cavity filled with liquid. Pitcher plants are adept at surviving in a nutrient-poor environment. They do so by luring insects, like ants, into their digestive juices by attracting them with the sweet smell of nectar. However, the success of this strategy depends upon the local climate, for their intended prey can escape if conditions are dry.
However, in the end the pitcher plants seem to win out, even in conditions of low humidity. Scientists have noted that the sticky trails left by the escapee insects later lead other insects into the plant traps.
Researchers have discovered this after studying young Nepenthes rafflesiana pitcher plants in Borneo. The scientists noted that the plants have slippery surfaces on their specialized pitcher-shaped leaves that , according to the research paper: “cause visitors to fall into the pitcher and drown in the digestive fluid.”
This phenomenon appears to occur regardless of the humidity level. The answer resolves a problem that has confounded botanists for many years: why are mature plants seemingly ineffective and have dry traps up to eight hours a day. To examine this further, the researchers compared the amount of prey caught by continuously wetted pitchers and leaves left alone on the same plant.
The researchers discovered that constantly wet pitchers caught more flying insects, but the untouched pitchers overall nabbed almost three times as many prey over the study period. Based on this, the researchers reasoned that alternating between ineffective and highly effective trap modes allows the plant to exploit the behavior of “scout” ants—those insects responsible for sourcing food and alerting their colonies to its location—by letting one ant escape in order to capture many more.
The research has been published in Proceedings of the Royal Society B. The paper is titled “How to catch more prey with less effective traps: explaining the evolution of temporarily inactive traps in carnivorous pitcher plants.”
