New Zealand plants show evidence of mimicry for self-defense: study

Can plants mimic another species to avoid being eaten as some animals do?

Maybe, according to a study of two New Zealand native plants that look identical, but taste very different.

The similarity could show the possible use of an age-old defense mechanism previously found only in animals, Victoria University researchers said Tuesday.

The study compared the size, shape and pigmentation of hundreds of leaves on the horopito and small toropapa plants, and found a perfect match.

"Small toropapa is often mistaken as horopito, also known as the New Zealand pepper tree," researcher Karl Yager said in a statement.

"Over a third of the leaves of the two species cannot be statistically distinguished from one another. Unless the plants are flowering or fruiting, the only fast way to tell them apart is to taste a leaf."

The exact match between horopito and small toropapa provided evidence of Batesian mimicry, a common evolutionary tool where unprotected species imitated harmful or poisonous species to protect themselves from predators.

"Because of horopito's pungent, hot peppery taste, that leaves one with a numb tongue when a leaf is chewed, it is unpalatable to predators," said Yager.

"On the other hand, the small toropapa is highly palatable and largely defenseless. It is possible that the small toropapa has evolved its leaves to resemble the horopito and confuse would-be predators," he said.

"To date nearly all the research on mimicry comes from animals and although this research does not prove Batesian mimicry in plants, it provides the first detailed evidence consistent with Batesian mimicry."

As small toropara were possibly eaten by New Zealand's now-extinct giant flightless bird, the moa, it was likely that it evolved in response to moa domination, Yager said.

"Unfortunately we can't directly test this, but it provides an exciting hypothesis for future studies on Batesian mimicry in plants." Endit