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The coevolution of cooperation and dispersal in social groups and its implications for the emergence of multicellularity.

Hochberg ME, Rankin DJ, Taborsky M - BMC Evol. Biol. (2008)

Bottom Line: In addition to the necessity of reducing conflict over effecting specialized tasks, differentiating groups must control the exploitation of the commons, or else be out-competed by more fit groups.The propensity for cheaters to disperse is highest with intermediate benefit:cost ratios of cooperative acts and with high relatedness.We suggest that trait linkage between dispersal and cheating should be operative regardless of whether groups ever achieve higher levels of individuality, because individual selection will always tend to increase exploitation, and stronger group structure will tend to increase overall cooperation through kin selected benefits.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institut des Sciences de l'Evolution, Centre National de Recherche Scientifique, UMR 5554, Université Montpellier II, 34095 Montpellier, France. mhochber@univ-montp2.fr

ABSTRACT

Background: Recent work on the complexity of life highlights the roles played by evolutionary forces at different levels of individuality. One of the central puzzles in explaining transitions in individuality for entities ranging from complex cells, to multicellular organisms and societies, is how different autonomous units relinquish control over their functions to others in the group. In addition to the necessity of reducing conflict over effecting specialized tasks, differentiating groups must control the exploitation of the commons, or else be out-competed by more fit groups.

Results: We propose that two forms of conflict - access to resources within groups and representation in germ line - may be resolved in tandem through individual and group-level selective effects. Specifically, we employ an optimization model to show the conditions under which different within-group social behaviors (cooperators producing a public good or cheaters exploiting the public good) may be selected to disperse, thereby not affecting the commons and functioning as germ line. We find that partial or complete dispersal specialization of cheaters is a general outcome. The propensity for cheaters to disperse is highest with intermediate benefit:cost ratios of cooperative acts and with high relatedness. An examination of a range of real biological systems tends to support our theory, although additional study is required to provide robust tests.

Conclusion: We suggest that trait linkage between dispersal and cheating should be operative regardless of whether groups ever achieve higher levels of individuality, because individual selection will always tend to increase exploitation, and stronger group structure will tend to increase overall cooperation through kin selected benefits. Cheater specialization as dispersers offers simultaneous solutions to the evolution of cooperation in social groups and the origin of specialization of germ and soma in multicellular organisms.

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Relatedness, r*, associated with simulations in Figure 4.
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Figure 5: Relatedness, r*, associated with simulations in Figure 4.

Mentions: Whereas in Model 1, the relative cost of cooperator (c) and cheater (e) dispersal did not yield a simple threshold condition for optimal outcomes (not shown), it did so for Model 2. We found that when cooperators and cheaters coexisted and e > c, cooperators dispersed and cheaters did not (i.e., σ * = 1) (Figs. 4a, b). The reverse held when c > e (Figs. 4c, d). Low effective group size (k) increases cooperator persistence (i.e., smaller areas in which n* = 0 in Fig. 4), with the effects on cheater persistence contingent on other parameters (i.e., differences in areas with n* = 0 in Fig. 4). More interestingly, whereas when e > c, lower k shifts the parameter space permitting cooperators and cheaters to coexist and has little effect on the area in which all cooperators disperse (y* = 1), when c > e, it expands the area of coexistence and that in which all cheaters disperse (z* = 1) (Fig. 4). Finally, relatedness (r*) generally increases with high P:s ratios, low k, and high costs to cooperator dispersal, c, with respect to cheater dispersal, e (Fig. 5). Interestingly, specialization in dispersal by cheaters and in sedentariness by cooperators tends to associate with high, but not the highest levels of relatedness (cf Figs. 4c, 5c).


The coevolution of cooperation and dispersal in social groups and its implications for the emergence of multicellularity.

Hochberg ME, Rankin DJ, Taborsky M - BMC Evol. Biol. (2008)

Relatedness, r*, associated with simulations in Figure 4.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2533331&req=5

Figure 5: Relatedness, r*, associated with simulations in Figure 4.
Mentions: Whereas in Model 1, the relative cost of cooperator (c) and cheater (e) dispersal did not yield a simple threshold condition for optimal outcomes (not shown), it did so for Model 2. We found that when cooperators and cheaters coexisted and e > c, cooperators dispersed and cheaters did not (i.e., σ * = 1) (Figs. 4a, b). The reverse held when c > e (Figs. 4c, d). Low effective group size (k) increases cooperator persistence (i.e., smaller areas in which n* = 0 in Fig. 4), with the effects on cheater persistence contingent on other parameters (i.e., differences in areas with n* = 0 in Fig. 4). More interestingly, whereas when e > c, lower k shifts the parameter space permitting cooperators and cheaters to coexist and has little effect on the area in which all cooperators disperse (y* = 1), when c > e, it expands the area of coexistence and that in which all cheaters disperse (z* = 1) (Fig. 4). Finally, relatedness (r*) generally increases with high P:s ratios, low k, and high costs to cooperator dispersal, c, with respect to cheater dispersal, e (Fig. 5). Interestingly, specialization in dispersal by cheaters and in sedentariness by cooperators tends to associate with high, but not the highest levels of relatedness (cf Figs. 4c, 5c).

Bottom Line: In addition to the necessity of reducing conflict over effecting specialized tasks, differentiating groups must control the exploitation of the commons, or else be out-competed by more fit groups.The propensity for cheaters to disperse is highest with intermediate benefit:cost ratios of cooperative acts and with high relatedness.We suggest that trait linkage between dispersal and cheating should be operative regardless of whether groups ever achieve higher levels of individuality, because individual selection will always tend to increase exploitation, and stronger group structure will tend to increase overall cooperation through kin selected benefits.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institut des Sciences de l'Evolution, Centre National de Recherche Scientifique, UMR 5554, Université Montpellier II, 34095 Montpellier, France. mhochber@univ-montp2.fr

ABSTRACT

Background: Recent work on the complexity of life highlights the roles played by evolutionary forces at different levels of individuality. One of the central puzzles in explaining transitions in individuality for entities ranging from complex cells, to multicellular organisms and societies, is how different autonomous units relinquish control over their functions to others in the group. In addition to the necessity of reducing conflict over effecting specialized tasks, differentiating groups must control the exploitation of the commons, or else be out-competed by more fit groups.

Results: We propose that two forms of conflict - access to resources within groups and representation in germ line - may be resolved in tandem through individual and group-level selective effects. Specifically, we employ an optimization model to show the conditions under which different within-group social behaviors (cooperators producing a public good or cheaters exploiting the public good) may be selected to disperse, thereby not affecting the commons and functioning as germ line. We find that partial or complete dispersal specialization of cheaters is a general outcome. The propensity for cheaters to disperse is highest with intermediate benefit:cost ratios of cooperative acts and with high relatedness. An examination of a range of real biological systems tends to support our theory, although additional study is required to provide robust tests.

Conclusion: We suggest that trait linkage between dispersal and cheating should be operative regardless of whether groups ever achieve higher levels of individuality, because individual selection will always tend to increase exploitation, and stronger group structure will tend to increase overall cooperation through kin selected benefits. Cheater specialization as dispersers offers simultaneous solutions to the evolution of cooperation in social groups and the origin of specialization of germ and soma in multicellular organisms.

Show MeSH
Related in: MedlinePlus