Little evidence of cheating among 'mutualist' species

Mutualists are species that benefit from each other's activity. Pollination is a classic example of mutualism.

Researchers have long assumed that cheating is rampant among mutualists. But a new study, published in the journal Ecology Letters, suggests the opposite is true.

As far as ecologists can tell from existing scientific literature, cheating is relatively rare among mutualist species.

There are a range of studies which claim to detail instances of mutualistic "cheating." But as scientists at Rice University, Michigan State and the University of California, Santa Barbara point out: these studies rarely operate under a standard (or accurate) definition of the word "cheating."

"By definition, a behavior is only cheating if it provides one partner with an advantage and also imposes a disadvantage on the other partner," Emily Jones, an evolutionary ecologist at Rice and co-author of the new study, said in a press release. "We found that most previous definitions were focused on just one side of the interaction."

"People have tended to be narrowly focused on whether one partner was either giving less of a resource or taking more from the other partner, but neither of those qualifies as cheating unless the other partner is harmed," Jones added.

This isn't to say that mutualism describes some sort of socialistic cooperative among animals. In fact, the idea of "cheating" is very much a reaction to the fact that mutualism, on its face, flies in the face of Darwinian self-interest.

But mutualism isn't about cooperation so much as exploitation. Ayn Rand's philosophy is very much alive in the natural world.

"Each species is actually exploiting the other, and each one benefits more from the mutual arrangement than they are harmed by it," said Jones.

Authors of the new study aren't actually arguing that cheating is non-existent, or even rare, only that previous research has failed to prove its prevalence.

"It is possible that cheating is widespread," said co-autho Maren Friesenr, a plant biologist at Michigan State. "But it is clear that previous studies have not proved that widespread cheating is taking place."

"In order to qualify as cheating," Friesen explained, "a behavior must increase the fitness of the cheating partner above the average fitness of individuals in its own population, and it must decrease the fitness of the partner below the average fitness of individuals in the partner's population."