In the scientific community it has been widely accepted that there is a large amount of cheating by members of mutualistic partnerships. According to a new study conducted by scientists at the National Center for Ecological Analysis and Synthesis (NCEAS) at UCSB, there is no concrete definition scientists use to define the word “cheating.”

The working group that conducted this analysis was led by Emily Jones, an evolutionary ecologist at Rice University in Houston, as well as Maren Friesen, a plant biologist at Michigan State University.

The highly social false killer whales and bottlenose dolphins form interpecies partnerships with each other during hunts to help themselves defend and avoid predators.

The highly social false killer whales and bottlenose dolphins form interspecies partnerships with each other during hunts to help themselves defend and avoid predators.

Jones explained, “understanding what mechanisms prevent cheating is a major part of understanding the evolution and persistence of [interspecies] cooperation,” a phenomenon that frequently occurs in the natural world. So, why does this occur if, according to Darwinian natural selection, all living organisms should act in their own self-interest, even if it is at the expense of another’s well being? Well, it seems that the definition of mutualism explains this query. According to an advisor of Friesen, in a mutualistic relationship both partners exploit one another and the benefits far outweigh the consequences. Therefore this self-interest then leads to cheating, because once a partner has taken as much as they need from their other partner, they will move on to the next partner. In simple terms, natural selection encourages species to cheat.

Given this background knowledge, the scientists reviewed a variety of studies on cheating among species that cooperate for a mutual benefit and found that there was no widespread common definition of cheating. It seemed that within most of the studies the researchers looked at, the definition of cheating was focused on only one side of the situation — the cheater or the one being cheated on. This way of looking at cheating only showed that one partner was taking more from his or her counterpart, but it doesn’t imply that the partner being cheated on was harmed.

Although the outcome of the study didn’t prove or disprove whether a large amount of cheating happens among mutualistic partnerships, it lead to a concrete definition of the word cheating.

“To be clear, we found that evidence of cheating is currently rare. That is different than there being evidence that cheating is rare,” Jones said.“Currently, most of our evidence is insufficient to determine how rare cheating is. However, theory does suggest that cheating should be rare, and thus I would not be surprised if the evidence eventually shows that cheating is rare.”

In order for one to be considered cheating on their partner, the cheating must improve the organism’s Darwinian fitness above the fitness of the rest of its species, while simultaneously decreasing the fitness of their partner far below the rest of their species. Jones explained why it is imperative to include the concept of species fitness in the definition of mutualistic cheating. This definition can be used all the time, across the board, in every situation.

“The common denominator in other definitions of cheating is that it is a threat to the persistence of cooperation. We wanted a definition that captured this threat but also specified how cheaters could be identified in a standard way,” Jones said. “Logically, in order for a behavior to be a threat to cooperation between mutualist species, it must both spread in one species and reduce the benefit of the interaction for partners in the other species. Both of these effects can best be measured through relative fitness. Additionally, relative fitness is something that can be compared meaningfully across different systems.”

This new definition of the word cheating will be very useful in future studies on mutualism by ending the confusion on what qualifies as cheating. By taking an interdisciplinary approach to this issue, this working group has gained a better understanding on how to define the actions done by the members of the mutual partnerships in our natural world.

A version of this story appeared on p. 14 of the Thursday, Oct. 1 print edition of the Daily Nexus.