---------- Forwarded message ---------- From: Dante-Gabryell Monson <[email protected]> Date: Thu, Oct 17, 2013 at 8:57 PM Subject: Biology - Research : How does cooperation survive cheating ? To: "[email protected]" <[email protected]>, " [email protected]" <[email protected]> http://www.pnas.org/content/109/47/19079.full.pdf * * *" We propose the “adaptive race” model: If during adaptation to an environment, the fitness gain of cooperators exceeds that of cheaters by at least the fitness cost of cooperation, the tragedy of the commons can be averted. Although cooperators and cheaters sample from the same pool of adaptive mutations, this symmetry is soon broken: The best cooperators purge cheaters and continue to grow, whereas the best cheaters cause rapid self-extinction. We speculate that adap- tation to changing environments may contribute to the persistence of cooperative systems before the appearance of more sophisti- cated mechanisms of cheater control. "* ... evolution of cooperation and cheating | experimental evolution | genetic hitchhiking | synthetic biology The cooperative act of paying a cost to produce a publicly available good is a common biological phenomenon. Human volunteers contribute their time to build Wikipedia, which can be used by anyone with Internet access. Throughout the animal kingdom, alarm calls are produced by individuals to warn others of danger, even though producing the call makes the caller more conspicuous (1). Microbes excrete a plethora of costly compounds that can be used by the producers and their neighboring cells to acquire nutrients that are hard to obtain, access favorable environments, or improve antibiotic resistance (2, 3). In biological systems, publicly available goods are generally “common goods,” because consumption by one individual reduces their availability to others. “Cheaters” use the common good without paying a cost to produce it. Thus, because the common good is equally accessible to all members of a population, cheaters, introduced through migration or mutation, will be more fit than cooperators, increase in frequency, and eventually exhaust the common good, leading to the “tragedy of the commons” (4). For instance, although cooperative viruses produce diffusible shared proteins required for viral reproduction, selfish viruses synthesize less but sequester more of these proteins and thereby displace cooperative viruses, lowering overall infectivity (5). Cancers, a leading cause of death globally (6), cheat by exploiting the common good produced by normal cells that cooperate to form a functional human body. Despite exploitation of common goods by naturally arising cheaters, cooperation persists (7–13). How does cooperation survive cheating? We first summarize mechanisms known to stabilize cooperation against cheating. Wethen describe our attempts to discover novel mechanisms of cheater control by excluding known ones from an engineered yeast cooperator–cheater system. ---------- Forwarded message ---------- From: tony Date: Thu, Oct 17, 2013 at 8:24 PM Subject: the tragedy of the commons averted To: Dante Cooperation via production of common goods is found in diverse life forms ranging from viruses to social animals. However, natural selection predicts a “tragedy of the commons”: Cheaters, benefit- ing from without producing costly common goods, are more fit than cooperators and should destroy cooperation. In an attempt to discover novel mechanisms of cheater control, we eliminated known ones using a yeast cooperator–cheater system engineered to supply or exploit essential nutrients. Surprisingly, although less fit than cheaters, cooperators quickly dominated a fraction of co- cultures. Cooperators isolated from these cocultures were supe- rior to the cheater isolates they had been cocultured with, even though these cheaters were superior to ancestral cooperators. Re- sequencing and phenotypic analyses revealed that evolved co- operators and cheaters all harbored mutations adaptive to the nutrient-limited cooperative environment, allowing growth at a much lower concentration of nutrient than their ancestors. Even after the initial round of adaptation, evolved cooperators still sto- chastically dominated cheaters derived from them. We propose the “adaptive race” model: If during adaptation to an environment, the fitness gain of cooperators exceeds that of cheaters by at least the fitness cost of cooperation, the tragedy of the commons can be averted. Although cooperators and cheaters sample from the same pool of adaptive mutations, this symmetry is soon broken: The best cooperators purge cheaters and continue to grow, whereas the best cheaters cause rapid self-extinction. We speculate that adap- tation to changing environments may contribute to the persistence of cooperative systems before the appearance of more sophisti- cated mechanisms of cheater control. http://www.pnas.org/content/109/47/19079.full.pdf -- P2P Foundation: http://p2pfoundation.net - http://blog.p2pfoundation.net <http://lists.ourproject.org/cgi-bin/mailman/listinfo/p2p-foundation>Updates: http://twitter.com/mbauwens; http://www.facebook.com/mbauwens #82 on the (En)Rich list: http://enrichlist.org/the-complete-list/