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Sudweeks, Jaye

University of British Columbia

The prevalence of cooperative behavior is a fundamental problem in evolutionary biology. Because cooperative behaviors impose a cost, cooperative individuals are vulnerable to exploitation by Defectors that do not contribute and instead benefit from the cooperation of others. The bacteriophage ϕ6 shows strategies of cooperation and defection during infection. While replicating inside a host cell, ϕ6 viruses produce essential proteins in the host cell cytoplasm. Because coinfection is possible, a virus does not have exclusive access to its own products. Cooperators viruses produce products while Defector viruses produce less and instead steal from Cooperators. Previous work found that ϕ6 is trapped in the prisoner’s dilemma, predicting that Defectors will replicate faster than Cooperators and out-compete them; cooperation is doomed. Still, cooperative ϕ6 exist, so there must be a mechanism that maintains cooperation. Defectors are advantaged when coinfection is common and there is ample opportunity to extort Cooperators. However, this advantage wanes when coinfection is less common, and Cooperators are advantaged when single infection is common. The rates of single infection and coinfection are modulated by the densities of hosts and viruses. We propose that environmental feedback, or the interplay between viral and host densities, might maintain cooperation in ϕ6 populations. We develop and analyze a mathematical model that incorporates environmental feedback and find that for many parameter combinations, environmental feedback leads to the co-existence of Cooperators and Defectors.

Text

2022-12-20

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/83447

Mathematics

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/