Modelos Computacionais para Estudar Processos de Especiação Simpátrica

• Autor(a) principal: Rosso, Karen Luz Burgoa
• Data de Publicação: 2005
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Repositório Institucional da Universidade Federal Fluminense (RIUFF)
• Texto Completo: https://app.uff.br/riuff/handle/1/19043
• topic: Física estatística; Termodinâmica; Simulação computacional; Biología evolutiva; Ecología evolutiva; Especiação simpátrica; Econofísica; Transiçoes de fase; CNPQ::CIENCIAS EXATAS E DA TERRA::FISICA

We perform simulations based on the Penna model for biological ageing, now with the purpose of studying sympatric speciation, that is, the division of a single species into two or more populations, reproductively isolated, but without any physical barrier separating them. For that we introduce a new kind of competition among the individuals, using a modified Verhulst factor. The new competition depends on some specific phenotypic characteristic of each individual, which is represented by a pair of bitstrings. These strings are read in parallel and have no age structure. In this way, each individual genome consists of two parts. The first one has an age-structure and is related to the appearance of inherited diseases; the second part is not structured and takes into account the competition for the available resources. We also introduce sexual selection into the model, making use of another non-structured and independent pair of bitstrings. In this thesis we present three different models; two of them use, besides the competition, a sudden change in the ecology to obtain speciation. They were motivated by the speciation process observed in the Darwin finches, a family of birds that inhabits the Galapagos Islands, and also by that observed in the cichlids, a family of fish that lives in the Nicaragua Lakes and in the Vitoria Lake, in Africa. The third model does not use any ecological change: sympatric speciation is obtained depending only on the strength of competition among individuals with similar phenotypic characteristics. In the model to describe the speciation process of the finches we use a single pair of non age-structured bitstrings to describe one phenotypic characteristic which is related to both competition and mating preference. This characteristic corresponds to the beak morphology. We study the changes in the distribution of the beaks according to the mating rules, to the values of the parameters and to the position of the species in a food-chain. In this case we obtain qualitative results that are in agreement with field observations of these birds. To simulate the cichlids, we use two pairs of non-structured and independent bitstrings. One pair represents the fish type of jaw and is directly related to competition for food. The other pair represents the colour, which is the trait related to sexual selection. Our main purpose has been to analyze the stability of the distributions of both jaws and colours. In this case we obtain sympatric spectiation, although not exactly the one experimentally observed in the cichlids. Using the model without ecological changes, we study the probability of speciation as a function of the competition strength and find a phase transition, which may allow the study of the reversibility or not of the speciation process.