Group selection often involves plausible models but require that

Group selection often involves plausible models but require that

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Group selection often involves plausible models but require that interdeme (group) selection be strong . Would have to be very strong to overcome selection among individuals within populations. Other complicating factors: turnover rate of individuals is faster than of populations/groups; fixation of less fit allele is unstable to invasion by new mutant allele or "selfish" allele introduced by gene flow. New research on multilevel selection suggests that there should not be the necessary association between altruism and "sacrifice" or genetic "suicide". Cooperation among individuals can actually result in higher group fitness without the assumed loss of individual fitness (see a meeting review in Science (9 August 1996) vol 273:739-740). D. S. Wilson makes the analogy between the optimal clutch size argument of D. Lack and the optimal group of Wynne-Edwards. With too many eggs in a clutch an individual may die trying to support them all, so some intermediate clutch size is
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Unformatted text preview: "optimal" (see Life History Lecture). Optimal groups may evolve intermediate density by the same trade-off mechanism. A further problem for group selection: with localize population structure, there can be considerable inbreeding which increases relatedness (r). Thus inter "group" selection that gives the appearance of evolution of altruistic traits may be mediated by kin selection due to the high relatedness among individuals. Later we will consider species selection . Some lineages have more species than others, but are these lineages more fit? Is this simply a pattern (more species) or is it really a different process ? Is it simple like bacteria in chemostats: a higher birth/death ratio; some lineages seem to speciate faster than their members go extinct? Is this mediated at the level of the species, or can we explain it (as G. C. Williams might like) at the level of individuals within populations?...
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