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  • A collection of individuals defined on the basis of common properties, used for the construction of a model of group selection.

    most ecological interactions, in terms of competition, mating, feeding and predation are carried out during the nondispersal stages in the smaller subdivisions, which I term “trait-groups.” In some cases the trait-groups are discrete and easily recognized, such as for vessel-inhabiting mosquitoes and dung insects. In other cases they are contenuous and each individual forms the center of its own trait-group, interacting only with its immediate neighbors, which comprise a small proportion of the deme. Two examples are plants and territorial animals. […] The process of group selection postulated here can be visualized […], showing two trait-groups with differing proportions of A and B types […]. The A-trait is an “altruistic” defense behavior, such as a warning cry. While the animals are in their trait-groups, predation occurs and within each trait-group the B’s fare better than the A’s. However, considering both groups together the opposite is true, that is, the A’s fare better than the B’s […]. This is because due to the A-trait, the trait-group with the most A’s has less overall predation upon it. Were the groups to remain in isolation this would mean nothing, and the A’s would rapidly be eliminated. However, all animals leave the trait-groups […], each has a single off-spring, and the population settles back into the trait-groups […]. The increasedproportionality of the A-type for the en tire system is now realized within each trait-group, and by this process B is eliminated from the system. Notice that this form of group selection never really violates the concept of individual selection. It is always the type with the highest per capita fitness that is chosen, but when the effect of more than one trait-group is considered, these are the very types that behave altruistically.

    Wilson, D.S. (1975). A theory of group selection. Proc. Nat. Acad. Sci. U.S.A. 72, 143-146: 143; 145. 


    since I do not think he [scil. D.S. Wilson] is discussing group selection, I do not find his argument convincing. In fact, it is not clear why Wilson does not regard his model as one of kin selection. […] If, for example, animals behave with an equal degree of altruism to all their “neighbors”, or to all fellow members of their “trait-group,” and if on average animals are related to their neighbors, then I would regard this as an example of kin selection. […] It is useful to distinguish as sharply as possible the processes of “kin” and “group” selection. The terms group selection should be confined to cases in which the group (deme or species) is the unit of selection. This requires that groups be able to “reproduce,” by splitting or by sending out propagules, and that groups should go extinct.

    Maynard Smith, J. (1976). Group selection. The Quarterly Review of Biology 51, 277-283: 282. 


    I have been critical of Wilson’s paper (Maynard Smith 1976), mainly for semantic reasons. It seems inappropriate to describe the process as ‘group selection’ since I would prefer to confine that term to cases in which the entities with the properties of multiplication, heredity, and variation, whose evolution is being described, are in fact the groups, and not individuals.

    Maynard Smith, J. (1983). Models of evolution. Proceedings of the Royal Society of London. Series B, Biological Sciences 219, 315-325: 319. 


    the meaning of the term group has been expanded to include short-lived groups, behaviorally formed groups, and “neighborhoods” whose boundaries are not obvious to the human eye. This expansion requires no changes in basic definitions or processes; it follows directly from a notion of groups whose duration is externally imposed, without Maynard Smith’s simplifying assumption that between dispersal episodes evolution within each group proceeds to fixation. Indeed, I have stressed that if one adheres strictly to the mathematical definition of groups, then the groups must be very small and defined separately for each trait (the trait group […]).

    Wilson, D.S. (1983). The group selection controversy: history and current status. Ann. Rev. Ecol. Syst. 14, 159-187: 175.


    I do not think that the trait-group selection of Wilson qualifies as group selection, because it is concerned with the effects of the interactions among individuals on the spread of genes, and not with the differential proliferation of the trait-groups themselves.

    Leigh, E.G. (1983). When does the good of the group override the advantage of the individual? Proceedings of the National Academy of Sciences of the United States of America 80, 2985-2989: 2985.