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Genes as Cues of Relatedness and Social Evolution in Heterogeneous Environments.

Leimar O, Dall SR, Hammerstein P, McNamara JM - PLoS Comput. Biol. (2016)

Bottom Line: We analyze a model of social evolution in a two-habitat situation with limited dispersal between habitats, in which the average relatedness at the time of helping and other benefits of helping can differ between habitats.An important result from the analysis is that alleles at a polymorphic locus play the role of genetic cues, in the sense that the presence of a cue allele contains statistical information for an organism about its current environment, including information about relatedness.Another important result is that the genetic linkage between a cue locus and modifier loci influences the evolutionary interest of modifiers, with tighter linkage leading to greater divergence between social traits induced by different cue alleles, and this can be understood in terms of genetic conflict.

View Article: PubMed Central - PubMed

Affiliation: Department of Zoology, Stockholm University, Stockholm, Sweden.

ABSTRACT
There are many situations where relatives interact while at the same time there is genetic polymorphism in traits influencing survival and reproduction. Examples include cheater-cooperator polymorphism and polymorphic microbial pathogens. Environmental heterogeneity, favoring different traits in nearby habitats, with dispersal between them, is one general reason to expect polymorphism. Currently, there is no formal framework of social evolution that encompasses genetic polymorphism. We develop such a framework, thus integrating theories of social evolution into the evolutionary ecology of heterogeneous environments. We allow for adaptively maintained genetic polymorphism by applying the concept of genetic cues. We analyze a model of social evolution in a two-habitat situation with limited dispersal between habitats, in which the average relatedness at the time of helping and other benefits of helping can differ between habitats. An important result from the analysis is that alleles at a polymorphic locus play the role of genetic cues, in the sense that the presence of a cue allele contains statistical information for an organism about its current environment, including information about relatedness. We show that epistatic modifiers of the cue polymorphism can evolve to make optimal use of the information in the genetic cue, in analogy with a Bayesian decision maker. Another important result is that the genetic linkage between a cue locus and modifier loci influences the evolutionary interest of modifiers, with tighter linkage leading to greater divergence between social traits induced by different cue alleles, and this can be understood in terms of genetic conflict.

No MeSH data available.


Evolutionary equilibrium dimorphisms.The equilibrium dimorphisms z1 and z2, color coded blue and red, are plotted as functions of the rate of recombination ρ between cue and modifier loci. The two habitats differ in the size of social groups, with N1 = 20 and N2 = 2, resulting in lower relatedness in habitat 1 (r1 = 0.05) than in habitat 2 (r2 = 0.5). Three examples are shown, labeled with the rate of migration between habitats: m12 = m21 = m = 0.01, 0.05, 0.10. The total population size is the same in both habitats, and the parameters for the public goods game are also the same: W1 = W2 = 0.5, b1 = b2 = 3.0, c1 = c2 = 1.5. The gray horizontal line shows the equilibrium of gradual evolution in a monomorphic population, which does not depend on m or ρ. The dark gray points (with error bars) at ρ = 0.0 and ρ = 0.5, shifted slightly left and right for visibility, show mean and standard deviation of the average phenotype over 10 replicate individual-based evolutionary simulations. In these simulations, ag in Eq (5) was encoded by a single locus whereas a0 was kept at a fixed value (see S1 Text for further explanation).
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pcbi.1005006.g002: Evolutionary equilibrium dimorphisms.The equilibrium dimorphisms z1 and z2, color coded blue and red, are plotted as functions of the rate of recombination ρ between cue and modifier loci. The two habitats differ in the size of social groups, with N1 = 20 and N2 = 2, resulting in lower relatedness in habitat 1 (r1 = 0.05) than in habitat 2 (r2 = 0.5). Three examples are shown, labeled with the rate of migration between habitats: m12 = m21 = m = 0.01, 0.05, 0.10. The total population size is the same in both habitats, and the parameters for the public goods game are also the same: W1 = W2 = 0.5, b1 = b2 = 3.0, c1 = c2 = 1.5. The gray horizontal line shows the equilibrium of gradual evolution in a monomorphic population, which does not depend on m or ρ. The dark gray points (with error bars) at ρ = 0.0 and ρ = 0.5, shifted slightly left and right for visibility, show mean and standard deviation of the average phenotype over 10 replicate individual-based evolutionary simulations. In these simulations, ag in Eq (5) was encoded by a single locus whereas a0 was kept at a fixed value (see S1 Text for further explanation).

Mentions: Fig 2 shows how the migration rate m between habitats and the recombination rate ρ between cue and modifier loci influence dimorphic evolutionary equilibria, i.e. phenotypes where the selection gradient Eq (7) vanishes. The blue and red curves indicate phenotypes z1 and z2 suited to habitats with low and high relatedness. The selection gradient is illustrated in Fig 3 for a few values of m and ρ, and the shaded regions in this figure show where a polymorphism at the cue locus is maintained. In this example, the only difference between habitats is the number of founders of a social group, with N1 = 20 in habitat 1 and N2 = 2 in habitat 2, so it is appropriate to interpret the genetic cue as a cue of relatedness.


Genes as Cues of Relatedness and Social Evolution in Heterogeneous Environments.

Leimar O, Dall SR, Hammerstein P, McNamara JM - PLoS Comput. Biol. (2016)

Evolutionary equilibrium dimorphisms.The equilibrium dimorphisms z1 and z2, color coded blue and red, are plotted as functions of the rate of recombination ρ between cue and modifier loci. The two habitats differ in the size of social groups, with N1 = 20 and N2 = 2, resulting in lower relatedness in habitat 1 (r1 = 0.05) than in habitat 2 (r2 = 0.5). Three examples are shown, labeled with the rate of migration between habitats: m12 = m21 = m = 0.01, 0.05, 0.10. The total population size is the same in both habitats, and the parameters for the public goods game are also the same: W1 = W2 = 0.5, b1 = b2 = 3.0, c1 = c2 = 1.5. The gray horizontal line shows the equilibrium of gradual evolution in a monomorphic population, which does not depend on m or ρ. The dark gray points (with error bars) at ρ = 0.0 and ρ = 0.5, shifted slightly left and right for visibility, show mean and standard deviation of the average phenotype over 10 replicate individual-based evolutionary simulations. In these simulations, ag in Eq (5) was encoded by a single locus whereas a0 was kept at a fixed value (see S1 Text for further explanation).
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4920369&req=5

pcbi.1005006.g002: Evolutionary equilibrium dimorphisms.The equilibrium dimorphisms z1 and z2, color coded blue and red, are plotted as functions of the rate of recombination ρ between cue and modifier loci. The two habitats differ in the size of social groups, with N1 = 20 and N2 = 2, resulting in lower relatedness in habitat 1 (r1 = 0.05) than in habitat 2 (r2 = 0.5). Three examples are shown, labeled with the rate of migration between habitats: m12 = m21 = m = 0.01, 0.05, 0.10. The total population size is the same in both habitats, and the parameters for the public goods game are also the same: W1 = W2 = 0.5, b1 = b2 = 3.0, c1 = c2 = 1.5. The gray horizontal line shows the equilibrium of gradual evolution in a monomorphic population, which does not depend on m or ρ. The dark gray points (with error bars) at ρ = 0.0 and ρ = 0.5, shifted slightly left and right for visibility, show mean and standard deviation of the average phenotype over 10 replicate individual-based evolutionary simulations. In these simulations, ag in Eq (5) was encoded by a single locus whereas a0 was kept at a fixed value (see S1 Text for further explanation).
Mentions: Fig 2 shows how the migration rate m between habitats and the recombination rate ρ between cue and modifier loci influence dimorphic evolutionary equilibria, i.e. phenotypes where the selection gradient Eq (7) vanishes. The blue and red curves indicate phenotypes z1 and z2 suited to habitats with low and high relatedness. The selection gradient is illustrated in Fig 3 for a few values of m and ρ, and the shaded regions in this figure show where a polymorphism at the cue locus is maintained. In this example, the only difference between habitats is the number of founders of a social group, with N1 = 20 in habitat 1 and N2 = 2 in habitat 2, so it is appropriate to interpret the genetic cue as a cue of relatedness.

Bottom Line: We analyze a model of social evolution in a two-habitat situation with limited dispersal between habitats, in which the average relatedness at the time of helping and other benefits of helping can differ between habitats.An important result from the analysis is that alleles at a polymorphic locus play the role of genetic cues, in the sense that the presence of a cue allele contains statistical information for an organism about its current environment, including information about relatedness.Another important result is that the genetic linkage between a cue locus and modifier loci influences the evolutionary interest of modifiers, with tighter linkage leading to greater divergence between social traits induced by different cue alleles, and this can be understood in terms of genetic conflict.

View Article: PubMed Central - PubMed

Affiliation: Department of Zoology, Stockholm University, Stockholm, Sweden.

ABSTRACT
There are many situations where relatives interact while at the same time there is genetic polymorphism in traits influencing survival and reproduction. Examples include cheater-cooperator polymorphism and polymorphic microbial pathogens. Environmental heterogeneity, favoring different traits in nearby habitats, with dispersal between them, is one general reason to expect polymorphism. Currently, there is no formal framework of social evolution that encompasses genetic polymorphism. We develop such a framework, thus integrating theories of social evolution into the evolutionary ecology of heterogeneous environments. We allow for adaptively maintained genetic polymorphism by applying the concept of genetic cues. We analyze a model of social evolution in a two-habitat situation with limited dispersal between habitats, in which the average relatedness at the time of helping and other benefits of helping can differ between habitats. An important result from the analysis is that alleles at a polymorphic locus play the role of genetic cues, in the sense that the presence of a cue allele contains statistical information for an organism about its current environment, including information about relatedness. We show that epistatic modifiers of the cue polymorphism can evolve to make optimal use of the information in the genetic cue, in analogy with a Bayesian decision maker. Another important result is that the genetic linkage between a cue locus and modifier loci influences the evolutionary interest of modifiers, with tighter linkage leading to greater divergence between social traits induced by different cue alleles, and this can be understood in terms of genetic conflict.

No MeSH data available.