All,
Nice job on choosing papers. Here is a summary of what I heard. Please comment on this post to add to, correct, or question my brief overview.
All readings can be found at:
http://micropopbio.org/cooper/2008/04/17/student-chosen-readings-for-evolution-of-community-structure-in-space-or-time/
In chronological order of publication,
1) Dave, who chose Bull JJ Molineaux IJ, Rice WR. 1991. Selection of benevolence in a host-parasite system. Evolution 45:875-82.
They evolved a plasmid pBR322-phage M13 chimera under high-fidelity (had to stick with E coli host) and low fidelity (were allowed to infect multiple partners) conditions. Found that each became more fit in the selective environment, and that high-fidelity phagemids lost the ability to infect horizontally as a consequence of a reduced phage genome.
2) Sam, who chose: Tamas Czaran, Rolf F. Hoekstra, and Ludo Pagie. 2002. Chemical warfare between microbes promotes biodiversity. PNAS.
Simulated the same basic rock-paper-scissors dynamic of Kerr et al, but allowed as many as 14 different toxin/antitoxin/susceptible combinations to evolve. Studied rates and influences of mutation and recombination in a spatial matrix. Found that a frozen state of coexistence of “hyperimmunity” is likely but can be disrupted by either recombination or asynchronous temporal scales of dominance between players (eg toxin killing is faster than resource competition). Very interesting discussion of their findings — see the paper.
3) Dan, who chose: R. Craig MacLean & Ivana Gudelj. 2006. Resource competition and social conflict in experimental populations of yeast. Nature.
Used two strains of yeast that were 1) capable of respiration and fermentation or 2) capable only of respiration. The latter was superior in head-to-head mixed competition under chemostat conditions in which glucose was not limiting. The 2 stably coexisted in batch culture owing to the need to ferment in stationary phase and because the cheater (no fermentation) was sensitive to toxic metabolic intermediates produced by its own growth. Also, from the article, “In agreement with our hypothesis, the itness of the cooperator at the level of the metapopulation is both positive frequency-dependent (F1,7 ¼ 55, P , 0.0001; Fig. 4) and negative density-dependent (F1,7 ¼ 41, P , 0.0001; Fig. 4), implying that a metapopulation of cooperators can resist invasion by a rare cheater provided that the number of cells that colonize each patch is below a critical threshold. Positive frequency-dependent selection for cooperation also implies that a rare cooperator cannot invade a
population of cheaters.”
4) Laura, who chose: Federico Prado. and Benjamin Kerr. 2007. THE EVOLUTION OF RESTRAINT IN BACTERIAL BIOFILMS UNDER NONTRANSITIVE COMPETITION. Evolution.
The authors modeled a system similar to the original Kerr paper involving colicin production, resistance, and sensitivity, and found that in structured communities containing these players, the players neither evolve maximum toxicity or resistance. That is, the conditions favor an intermediate state of restraint.
5) Abe, who chose: Brockhurst, MA. Population Bottlenecks Promote Cooperation in Bacterial Biofilms.
http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0000634/trackback
Reasoning that kin selection is strongest in smaller populations where the probability of genetic relatedness among individuals is highest, the author tested effects of bottleneck size on the evolution and stability of cooperative traits in the Ps. fluorescens system of Rainey, Travisano, et al. From the text: “In line with predictions, the frequency of evolved cheats within the populations increased with increasing bottleneck size. This result highlights the importance of ecologically mediated population bottlenecks in the maintenance of social traits in microbes.”
Sanjuro, I welcome your addition, and others, please feel free to comment!
