[P2P-F] Fwd: Biology - Research : How does cooperation survive cheating ?

Fri Oct 18 13:16:58 CEST 2013

---------- Forwarded message ----------
From: Dante-Gabryell Monson <dante at ecobytes.net>
Date: Thu, Oct 17, 2013 at 8:57 PM
Subject: Biology - Research : How does cooperation survive cheating ?
To: "econowmix at googlegroups.com" <econowmix at googlegroups.com>, "
global-survival at googlegroups.com" <global-survival at googlegroups.com>

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

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