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EVOLUTION OF ALTRUISM IN KIN‐STRUCTURED AND RANDOM SUBDIVIDED POPULATIONS
Author(s) -
Fix Alan G.
Publication year - 1985
Publication title -
evolution
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.84
H-Index - 199
eISSN - 1558-5646
pISSN - 0014-3820
DOI - 10.1111/j.1558-5646.1985.tb00433.x
Subject(s) - metapopulation , biology , kin selection , extinction (optical mineralogy) , population , evolutionary biology , gene flow , demography , genetics , genetic variation , biological dispersal , gene , sociology , paleontology
A. population structure favorable to the evolution of an altruistic trait is studied by Monte Carlo simulation. The model is based on a small‐scale nonindustrial human society but seems generalizable to other highly social mammals. Three hierarchical levels are recognized: 1) the ecologically isolated local group (hamlet) which may be composed of kin and/or unrelated individuals; 2) the deme (settlement) comprising several such groups which interbreed; and 3) the set of demes (metapopulation) among which gene flow occurs. The first two levels of the model are based on D. S. Wilson's structured deme concept; the third allows for gene flow among demes in the metapopulation and for the structured diffusion of alleles across a wider area than might be included within the scope of a single deme. The simulation models genetic drift by a process of hamlet formation which may be random, or variously kin‐structured. Hamlets may then become extinct based on a probability function of their gene frequencies. Individual selection within settlements is modeled deterministically, and gene flow among settlements is modeled as two‐dimensional steppingstone migration of random or kin‐structured groups. Results of the simulations show that, with realistic values for group sizes, moderate extinction rate, and high rates of migration ( m > 27%), disadvantageous alleles ( s = 10% and 25%) may increase markedly due to differential hamlet extinction over the course of 50 generations. The greater the degree of kin‐structuring of founder groups, the higher the variance among hamlets and the faster the rate of increase of the allele for altruism. Nonetheless, even in some randomly founded groups, a clear increase in the altruism gene frequency occurred. It is also notable that kin‐structured group selection by hamlet extinction may be effective when the initial frequency of altruism genes is very low (average of one per deme) and among a relatively small number of demes (25). Thus the process of group extinction in a hierarchically structured population allows rapid increase of an allele for altruism under plausible demographic conditions.