Mutualism evolution on heterogeneous landscapes
While mutually beneficial interactions are common in nature, their persistence poses numerous theoretical problems. Mutualistic partnerships involve reciprocal cooperative actions between species that imply a cost for the actor and a benefit for the receiver. In principle, cooperators can easily become exploited by cheaters that accept cooperative acts without returning them. Such exploitation can be avoided when cooperators can identify cheaters and either forego or exit such partnerships, which is facilitated by interactions occurring on a local scale. Another mechanism is for cooperators to choose among potential partners according to their “offers”, just like goods are offered and chosen on a marketplace. These two mechanisms are known as partner fidelity and partner choice, respectively, and frequently occur together. My plan is to work out and study a model of mutualism evolution incorporating these combined effects. In particular, the formation of mutualistic partnerships (with participation of two or more individuals) will be driven by potential partners choosing others according to their initial offers or signs. The persistence of mutualistic partnerships will also depend on the level of “satisfaction” of the participants regarding the benefits they have received, in accordance with a “win stay-lose shift” strategy. Individuals can differ in their potential to find partners, in their cost of maintaining partnerships of different quality, and in their ability to sanction cheaters. Partner fidelity and partner choice lead to a diverse and rapidly changing interaction topology. My aim is to investigate how such a setup can favor the evolution and maintenance of high levels of mutualistic interactions by suppressing the spread of cheaters.