Group selection models in pre-biotic evolution / Modelos de seleção de grupo em evolução pré-biótica




Group selection was proposed initially within an ecological context as an evolutionary selective force acting on a group in the same way as the individual selection does on the individuals composing the population. Despite the initial resistance of the conservative evolutionary biologists concerning the ideas of group selection, in the last decades those concepts have been very useful in the investigation of other problems not very correlated to its original motivation. In the first part of this thesis, we investigate a group selection model based on differential extinction as a selective force. In this model, the population is divided into groups, which in the context of group selection are termed demes. The demes are inhabited by two different types of individuals, namely, altruists and non-altruists, which are capable of reproducing themselves, mutating to the other type, or migrating to another deme. The population dynamics is formulated resorting to the transition matrices associated to those events, resulting in a set of coupled recursion equations describing the time evolution of the frequencies of the different types of demes in the population. Considering first the deterministic regime, which corresponds to the limit of infinite demes, each deme containing only a finite number of individuals, this model reveals the destabilizing role of the mutation mechanism on the altruistic demes. Following that analysis, we investigate a stochastic version of the above model, in which the number of demes is finite. The focus was on the effects of the finiteness of the population in the stationary frequencies of the demes. We verified that the instability of the altruistic state due to mutations becomes even more pronounced when the number of demes is reduced. Finally, we investigate a model for the evolution of enzymes production using the concepts of trait-group selection. This kind of group selection is based on the definition of the average subjective frequency, which is estimated by considering the structure of the population. We propose a new mathematical formulation to this problem, which we then use to study a recently proposed model to describe the evolution of altruistic features.


evolution group selection seleção de grupo altruism evolução altruísmo

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