Statistical and Mathematical Modeling in Biological Applications
Minus VAN BAALEN
Abstract: Many bacteria produce siderophores to scavenge for iron in their environment. Why there exist so many different types of siderophores, and how this diversity has arisen and is maintained is less clear. We suggest that diversity arises from the interplay between siderophore producing (cooperators) and non-producing individuals (cheaters): when there are many cheaters exploiting a siderophore type it would be beneficial for a mutant to produce a siderophore that is incompatible with the dominant population. We analyzed a mathematical model of metapopulations to investigate the potential for the emergence of diversity. We found that diversity indeed collapses in the metapopulation when cheaters are absent. When present, cheaters act as a controlling agent, rare most of the time and invading when one strain of cooperator becomes too common, preventing any strains of cooperators from dominating the others: they counteract genetic drift by regulating the populations of cooperators, and hence promote diversity. The consequences of our results for the appreciation of cheating in more general contexts will be discussed.