According to a common cliché, “Nature is cruel.” However, a study recently completed by a team of biologists and economists, including the University of Toronto’s Megan Frederickson, suggests otherwise. While it is true that species tend to work for their own self-interest, they can often achieve their goals by working cooperatively with other species in their environment.

“This project grew out of an interest in collaborating with an economist to use the idea of costly punishment as an analogy for a process that occurs in nature,” says Frederickson, an assistant professor in U of T’s Department of Ecology and Evolutionary Biology. Her main research focuses on various forms of mutualism — cases in which different species cooperate in order to achieve their own interests. One example of this occurs in plants that provide food and shelter for ants, which in turn prevent the plants from being consumed by insect herbivores.

Frederickson’s research is primarily focused on cases of cheating in these mutualisms: she wants to know what prevents one partner from reaping all the benefits of the cooperative arrangement, while not putting in the work.
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“There are some pollinators that rob host plants of nectar, but fail to do their part of spreading pollen. Some ants feed off plants but don’t deter herbivores. Very often these species start out as cooperators in a mutualism, but they managed to reap benefits while paying no cost or a reduced cost. Also, sometimes species outside of the mutualism to begin with enter into one.”

In this particular project, which was published in September in Proceedings of the National Academy of Sciences, Frederickson collaborated with economist Glen Weyl and biologist Naomi Pierce from Harvard University, as well as Douglas Yu, a biologist at the University of East Anglia. Looking at the relationships between the yucca tree and moths; legumes and nitrogen-fixing bacteria; and plants and ants, they concluded that, in the vast majority of cases, there is no punishment for species that cheat.

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“It is interesting to look at this process in terms of costly punishment — when you get a case where one species cheats, does the other punish it? According to our study, hosts normally do not punish cheaters at a cost to themselves. We are suggesting that the reason for this lack of retribution is that it is ultimately in each species’ self-interest to uphold its end of the bargain and avoid cheating,” Frederickson stated. “It’s a subtle point, but an interesting one.”

She adds that this research was enriched by her collaboration with economist Glen Weyl. “It was interesting to think about this idea in relation to the idea of costly punishment, which is the belief that society demands retribution for a crime. However, you can also imagine the criminal justice system in positive terms, as a form of rehabilitation. This scenario is analogous to what happens in mutualism. There is no evidence that bad behaviour is punished retributively, but that the species seek the rewards of working well.”

Frederickson notes that at the end of the day, this “kindness” between species really amounts to nothing more than self-interest. “My work shows how cooperative behaviour can be beneficial to other parties, but the reason cooperation evolves is because it results in higher individual fitness.”

She also notes that in many cases, the cooperative behaviour is purely unintentional. “In the case of pollinators, they happen to pick up pollen while seeking nectar; they end up serving the plant’s needs as a result of serving their own.”

In this interdisciplinary project, economic processes are applied to biological ones — not the other way around. “This theory is not being applied to human problems,” Frederickson explains. “But it can be useful when thinking about such issues as labour/management relations, in which employer and employee work cooperatively in order to gain different benefits. The obvious difference with humans is that we have an external system that polices us; plants and animals do not.”
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Frederickson stated that, at this stage, the team’s research is purely theoretical. “Our theory was formed on existing data. The real contribution is that Weyl developed a mathematical model of the cheating behaviour in order to determine if costly punishment was what was occurring. He was able to show the difference between a system regulated by punishment and a ‘passive feedback’ system in which neither partner monitors the other. The next step will be to test this theory out empirically.”

“It is interesting to look at this process in terms of costly punishment — when you get a case where one species cheats, does the other punish it?

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