The interplay between altruistic and selfish behaviour in biological populations may play a major role in habitat diversification and biodiversity, according to UBC researchers. Mathematicians have long used evolutionary 'game theory' to investigate why organisms appear to act in ways that benefit other members of their population, but are detrimental to themselves. Now researchers at UBC have added population dynamics and migration to the venerable mathematical model to propose a new reason why self-destructive behaviour survives in nature.
"Organisms that act in altruist ways interact with cheaters—organisms that basically look out for themselves—in a way that alters and shapes their environments," says Christoph Hauert, Assistant Professor of Mathematics at UBC. "The feedback between evolutionary and population dynamics helps co-operators cluster around and protect common resources. Those physical formations help co-operators survive in situations where cheaters would typically drive the entire population to extinction."
The findings—published today in the Proceedings of the National Academy of Sciences—could offer a new way to model habitat diversity and species co-existence, and suggest mechanisms to promote biodiversity. But the mathematical model could also have negative implications when applied to pathogenic microbial populations and antibiotic resistance. "This findings also suggest that spatial factors--room to migrate and cluster--increases the likelihood of the development of antibiotic resistance in certain types of bacteria," notes Hauert.
"From the perspective of the bacteria, the enzyme production that increases resistance is an act of cooperation because it is costly and benefits everyone else in the neighbourhood. From our perspective this kind of cooperation is, of course, most unwelcome." Altruistic behaviour abounds in nature. Examples include species that share food with non-hunting members of the group, worker bees that care for the queen bee and never mate, and animals that risk themselves by warning the group of the approach of predators. A key question is why the behaviour survives in populations when evolution should favour selfish behaviour.
Hauert worked on the project with colleagues Martin Nowak from Harvard and Joe Yuichiro Wakano at the Meiji Institute for Advanced Study of Mathematical Sciences.
The paper, along with an interactive lab allowing users to control the mathematic model behind the findings, are available online: Proceedings of the National Academy of Sciences www.pnas.org VirtualLabs in Evolutionary Game Theory www.univie.ac.at/virtuallabs
