A tree vine with chameleon-like skills that can mimic the leaves of almost any tree it climbs on has been discovered in Chile. The Boquila trifoliolata, which just may be the most resourceful impressionist in the forest, is the first plant found to practice “memetic polymorphism,” or the ability of species to change their appearance in different ways depending on its environment.
B. Trifoliota is native to Chile and Argentina, where it has been found entwined around a variety of trees and bushes, with its leaves almost always matching the host. Published in Current Biology this month, the research is the work of Ernesto Gianoli, who studies plants in Chile’s temperate rainforests, and Fernando Carrasco-Urra, an undergraduate student who works with Gianoli. They are trying to solve the mystery of B. Trifoliota in experiments by exposing the vine to a variety of hosts and moving it from one tree or bush to another to see if and how it changes.
Mimicry, called crypsis in a plant, is common in nature but is found mostly in animals, and is usually a protection ability. For instance, harmless king snakes look like poisonous cobras. Some butterflies grow large spots on their wings that look like the eyes of an owl. The B. Trifoliota’s chameleon abilities protect the vine by camouflaging it from plant-eating bugs. Climbing helps protect it from ground plant eaters, but if it hides in leaves it is even safer.
Most mimics, plant or animal, have the ability to imitate only one specific model. It was previously thought that butterflies were the only species able to do mimetic polymorphism, but B. Trifoliota has the master ability to mimic the appearance of the nearest leaf, even if that leaf does not belong to the tree the vine has climbed.
In three-quarters of cases, the leaves of B. Trifoliota are similar to the tree or bush they are found in, matching size, area, length of stalk, angle, and color. It can even match vein patterns on the other leaves, or grow a spiny tip if it climbs a shrub with spine-tipped leaves. It seems that the only thing it does not do well is match serrated leaves, although it does manage some resemblance. B. Trifoliota leaves can vary up to 10 times in size from smallest to largest, and their color can range from light to very dark.
The vine can even resemble several trees or bushes simultaneously if it crosses from one plant to another, but it was found that the unusual leaves only turn up when there are other leaves to mimic. If B. Trifoliota climbs a bare tree it just looks like a vine.
It is not known how B. Trifoliota figures out what the host tree looks like so it can mimic it. It may be small cues from odors or chemical secretions, or perhaps airborne chemicals released by the other tree. Environmental factors like light are not the reason. Gianoli and Carrasco-Urra found different modifications of B. Trifoliota leaves in very similar light levels. Although considered an unlikely theory, the vine’s master mimicry skills may be using genes from the host to identify what its leaves look like, as genes often transfer from one plant type to another by a microbe or parasite. DNA tests are planned to verify whether this is the case.
By Beth A. Balen