For almost every organism there are large gaps in our knowledge about the processes that leads to speciation. The changes an organism undergoes before divergence has occurred have remained a mystery, as it is difficult to say whether or not a species is going to diverge and when. To investigate this unknown the European whitefish (Coregonus lavaretus) and the northern pike (Esox lucius) were studied, as they produce a repeatable and predictable pattern of speciation in sympatry. To investigate the changes in phenotypes and behaviour in whitefish that precedes divergence, two lake populations were examined, Gräsvattnet and Ringsjön. Gräsvattnet was used as a control, with a population of whitefish but an absence of pike, whereas Ringsjön has a population of whitefish that invaded from Gräsvattnet and a pike population. The presence of pike presumably exerts divergent selection on the whitefish population. Fish and zooplankton were surveyed in both lakes from 1970 to the present day, which allows us to compare how whitefish populations and their resources change in the presence and absence of pike. The results found in Ringsjön show; (1) a change in habitat use, (2) a change in diet from pelagic to benthic, (3) an increase in the relationship between individual body size and diet and (4) a decrease in average size over the course of the study. (1)The presence of pike is believed to have forced the whitefish into the pelagic which could be seen in the result, with an increase in individuals caught in the pelagic. (2) The change in diet is thought to be caused by a resource competition created by individuals being forced to use the pelagic. Although insignificant this led to an overall reduction in zooplankton abundance by almost 40% which could have intensified competition. The resource competition could then have been intensified further by the change in composition of zooplankton relative abundance. (3) The increase in relationship between individual body size and diet is thought to increase due to the resource competition between smaller and larger individuals in the pelagic. Smaller individuals are better competitors than larger individuals for pelagic resource which could have led to the larger individuals switching to a more benthic diet. (4) The decrease in average size is thought to be caused by negative selection for larger individuals. Larger individuals have switched to a more benthic diet, and although the individuals are larger they still face the risk of predation in the littoral zone as they have not outgrown the gape size of the pike. This could have led to the average size reduction that may be the first steps in speciation, and ultimately leading to the divergence of two morphs by sympatric speciation in Ringsjön. In Gräsvattnet over the course of the study there were few and small changes in whitefish size, zooplankton relative abundance in the diet and in the environment. The results in Gräsvattnet could however suggest resource competition for benthic resources. Although resource competition is thought to be an important factor in the speciation of whitefish, without predation pressure no speciation occurs. This result could suggest the importance of predation pressure in the speciation of whitefish.

No description available.

Divergence in the face of gene flow is perhaps the most wildly disputed subject among researchers through time. The debate is an old one and we find its origin as far back as the era of Darwin. The theories dealing with sympatric and parapatric speciation, its processes and ecological conditions, are numerous and the empirical data supporting the ideas is constantly growing. However, the reach of a consensus almost seem as distant as ever. Two fundamental prerequisites can be identified for the evolution of divergence with gene flow, the act of disruptive selection, and the development of assortative mating. A set of models in which speciation with gene flow seem particularly likely is when a shift occurs in host preference in phytophagous insects and mating takes place on the host. In the work behind this thesis, the role of assortative mating in the initial stages of sympatric and parapatric speciation has been studied, as has the interaction between assortative mating and inbreeding and how it effects speciation in small sympatric populations, an aspect not much attended to earlier in the literature. My results show that assortative mating based on resource preference, can evolve rapidly upon secondary contact, and even in parapatric populations with a migration rate of 8% (13-15 individuals) per generation. However for assortative mating to be maintained selection against hybrids is needed. My results also suggests that small inbred populations have a hard time coping with strong assortative mating an as a consequence tend to relax their mating preferences to avoid inbreeding depression. Based on these results, I advocate for the importance of considering not only assortative mating in itself, but also the joint effects of assortative mating and inbreeding when dealing with theories of speciation with gene flow.

Apresenta-se nesta tese os resultados de aplicações do formalismo da Mecânica Estatística em dois problemas independentes. O primeiro diz respeito a um modelo para Evolução do Acasalamento Preferencial no processo de Especiação Simpátrica; enquanto que o segundo refere-se ao desenvolvimento de um algoritmo de aprendizado por meio de Inferência Aproximativa. No problema biológico estudado, cada indivíduo em um modelo de agentes é composto por dois traços. Enquanto um é responsável pela ecologia do indivíduo, o outro dita uma aparência física descorrelacionada com a adaptabilidade. Esses traços são expressos por diferentes loci que estão ligados entre si por uma taxa de recombinação. O modelo inclui também a possibilidade de evolução da preferência sexual dos indivíduos. Foi construído para esse modelo um diagrama de fases no espaço dos parâmetros que descrevem o ambiente como, por exemplo, quantidades de recursos e deficiência do indivíduo híbrido. Foram encontradas três fases de equilíbrio: (i) emergência de Acasalamento Preferencial; (ii) extinção de um dos alelos do locus responsável pela ecologia e (iii) equilíbrio Hardy-Weinberg. Foi verificado que o acasalamento preferencial pode emergir ou mesmo ser perdido (e vice-versa) em resposta a mudanças no ambiente. Além disso, o sistema apresenta memória característica típica de transições de primeira ordem, o que permitiu a descrição desse sistema biológico por meio do arcabouço da Mecânica Estatística. Em relação à Inferência Aproximativa, está-se interessado na construção de um algoritmo de aprendizado supervisionado por meio da técnica de Propagação de Expectativas. Mais especificamente, pretende-se inferir os parâmetros que compõem um Perceptron Professor a partir do conjunto de pares - entradas e saídas - que formam o conjunto de dados disponíveis. A estimativa desses parâmetros será feita pela substituição de uma distribuição Posterior original, geralmente intratável, por uma distribuição aproximativa tratável. o algoritmo Propagação de Expectativas foi adotado para a atualização, passo a passo, dos termos que compõem essa distribuição aproximativa. Essa atualização deve ser repetida até que a convergência seja atingida. Utilizando o Teorema do Limite Central e o método de Cavidade, foi possível obter um algoritmo genérico e que apresentou desempenho bastante evidente em dois modelos estudados: o modelo do Perceptron Binário e o modelo do Perceptron Gaussiano, com desempenho ótimo em ambos os casos. / This thesis presents applications of the framework of Statistical Mechanics to two independent problems. The first corresponds to a computational model for the evolution of Assortative Mating in the Sympatric Speciation process; and the second a learning algorithm built by means of a Bayesian Inference approach. In the biological problem each individual in an agent-based model is composed of two traits. One trait, called the ecological trait, is directly related with the fitness; the other, called the marker trait, has no bearing on the fitness. The traits are determined by different loci which are linked by a recombination rate. There is also the possibility of evolution of mating preferences, which are inherited from the mother and subject to random variations. The study of the phase diagram in the spa e of parameters describing the environment (like carrying capacity and disruptive selection) reveals the existence of three phases: (i) assortative mating; (ii) extinction of one allele from ecological loci; and (iii) Hardy-Weinberg equilibrium. It was verifed that the assortative mating an emerge or even be lost (and vice-versa) acording with the environmental hanges. Moreover, the system shows memory of the initial condition, characterising a hysteresis. Hysteresis is the signature of first order phase transition, which allows the description of the system by means of the Statistical Mechanics framework. In relation to the Bayesian Inference, a supervised learning algorithm was constructed by means of the Expectation Propagation approach. The idea is to estimate the parameters which compose a Teacher Perceptron by the substitution of the original posterior distribution, intra table, by a tractable approximative distribution. The step-by-step update of the terms composing the approximative distribution was performed by using the Expectation Propagation algorithm. The update must be repeated until the convergence ocurrs. Using the Central Limit Theorem and the Cavity Approah, it was possible to get a generic algorithm that has shown a very good performance in two application scenarios: The Binary Perceptron Model and the Gaussian Perceptron Model.

Apresenta-se nesta tese os resultados de aplicações do formalismo da Mecânica Estatística em dois problemas independentes. O primeiro diz respeito a um modelo para Evolução do Acasalamento Preferencial no processo de Especiação Simpátrica; enquanto que o segundo refere-se ao desenvolvimento de um algoritmo de aprendizado por meio de Inferência Aproximativa. No problema biológico estudado, cada indivíduo em um modelo de agentes é composto por dois traços. Enquanto um é responsável pela ecologia do indivíduo, o outro dita uma aparência física descorrelacionada com a adaptabilidade. Esses traços são expressos por diferentes loci que estão ligados entre si por uma taxa de recombinação. O modelo inclui também a possibilidade de evolução da preferência sexual dos indivíduos. Foi construído para esse modelo um diagrama de fases no espaço dos parâmetros que descrevem o ambiente como, por exemplo, quantidades de recursos e deficiência do indivíduo híbrido. Foram encontradas três fases de equilíbrio: (i) emergência de Acasalamento Preferencial; (ii) extinção de um dos alelos do locus responsável pela ecologia e (iii) equilíbrio Hardy-Weinberg. Foi verificado que o acasalamento preferencial pode emergir ou mesmo ser perdido (e vice-versa) em resposta a mudanças no ambiente. Além disso, o sistema apresenta memória característica típica de transições de primeira ordem, o que permitiu a descrição desse sistema biológico por meio do arcabouço da Mecânica Estatística. Em relação à Inferência Aproximativa, está-se interessado na construção de um algoritmo de aprendizado supervisionado por meio da técnica de Propagação de Expectativas. Mais especificamente, pretende-se inferir os parâmetros que compõem um Perceptron Professor a partir do conjunto de pares - entradas e saídas - que formam o conjunto de dados disponíveis. A estimativa desses parâmetros será feita pela substituição de uma distribuição Posterior original, geralmente intratável, por uma distribuição aproximativa tratável. o algoritmo Propagação de Expectativas foi adotado para a atualização, passo a passo, dos termos que compõem essa distribuição aproximativa. Essa atualização deve ser repetida até que a convergência seja atingida. Utilizando o Teorema do Limite Central e o método de Cavidade, foi possível obter um algoritmo genérico e que apresentou desempenho bastante evidente em dois modelos estudados: o modelo do Perceptron Binário e o modelo do Perceptron Gaussiano, com desempenho ótimo em ambos os casos. / This thesis presents applications of the framework of Statistical Mechanics to two independent problems. The first corresponds to a computational model for the evolution of Assortative Mating in the Sympatric Speciation process; and the second a learning algorithm built by means of a Bayesian Inference approach. In the biological problem each individual in an agent-based model is composed of two traits. One trait, called the ecological trait, is directly related with the fitness; the other, called the marker trait, has no bearing on the fitness. The traits are determined by different loci which are linked by a recombination rate. There is also the possibility of evolution of mating preferences, which are inherited from the mother and subject to random variations. The study of the phase diagram in the spa e of parameters describing the environment (like carrying capacity and disruptive selection) reveals the existence of three phases: (i) assortative mating; (ii) extinction of one allele from ecological loci; and (iii) Hardy-Weinberg equilibrium. It was verifed that the assortative mating an emerge or even be lost (and vice-versa) acording with the environmental hanges. Moreover, the system shows memory of the initial condition, characterising a hysteresis. Hysteresis is the signature of first order phase transition, which allows the description of the system by means of the Statistical Mechanics framework. In relation to the Bayesian Inference, a supervised learning algorithm was constructed by means of the Expectation Propagation approach. The idea is to estimate the parameters which compose a Teacher Perceptron by the substitution of the original posterior distribution, intra table, by a tractable approximative distribution. The step-by-step update of the terms composing the approximative distribution was performed by using the Expectation Propagation algorithm. The update must be repeated until the convergence ocurrs. Using the Central Limit Theorem and the Cavity Approah, it was possible to get a generic algorithm that has shown a very good performance in two application scenarios: The Binary Perceptron Model and the Gaussian Perceptron Model.

Natural populations exhibit a non-random mating behavior and it is assumed that mate preferences causing the non-random mating behavior play a role in sympatric speciation. In my thesis, I have proposed a new model of a mate preference that is based on ecological performance and I have named it fitness-based mating. Individuals that express this mate preference choose primarily fit partners. Fitness-based mating is modelled for haploid, diallelic populations. Individuals are distributed across two niches, and genomes are simplified to two loci. The first locus is subject to natural selection, and the second-locus genotype gives the strength of the mate preference. The population is separated into females and males, among which only females exhibit the mate preference. Ecological selection acts on both sexes alike. With the model I have investigated how female choosiness based on direct advantages offered by their partners can cause and maintain a polymorphic population. Fitness-based mating is an evolutionary successful mating strategy. It spreads in a population due to its amplifying effect on the reproductive success and on the attractiveness of its carriers. A polymorphism arises naturally in the model. The emergence of a stable polymorphism of traits underlying ecological selection is of special interest, because a polymorphism can be a precursor of speciation.

La présent étude examine aspect de l'écologie chimique de la Pyrale du maïs (Ostrinia nubilalis, Hübner, Lepidoptera: Crambidae). L’isolement reproducteur des phérotypes et leur spécialisation à la plante hôte ont reçu une attention particulière. Toutes les expériences ont été conçues pour avoir des informations pertinents sur le plan écologique des signaux chimiques libérés ou perçu par la Pyrale du maïs pendant la période de reproduction. La plupart des travaux en cadre de cette thèse dans des conditions naturelles et en tenant compte de tous les traits comportementaux de la Pyrale. Premièrement, le paysage chimique du champ de maïs a été étudié pour connaître les signaux chimiques rencontrés par une femelle de Pyrale du maïs qui est à la recherche d’une plante hôte. Les mélanges des volatiles qui composent l'environnement olfactif du champ de maïs a été identifié et leurs rôles discutés selon la biologie et le comportement d’oviposition de la Pyrale du maïs.Deuxièmement, en tenant compte de la périodicité du comportement de la Pyrale du maïs nous avons étudié les modifications circadiennes des profils des volatiles libérés par les plantes individuelles du maïs et par le champ du maïs.Troisièmement, le fidélité d’hôte plantes de la Pyrale du maïs a été étudié. Les volatiles libérés par différentes plantes hôtes au moment de vol d’oviposition ont été identifiés et le comportement de ponte a été étudié dans le tunnel du vol.Quatrièmement, les signaux chimiques impliqués dans l'isolement reproducteur des phérotypes de la Pyrale du maïs a été étudié. Nous nous sommes concentrés sur la phéromone mâle produite par les pinceaux androconiaux et sur leur rôle dans le comportement de cour. / The present PhD study investigates the aspect of chemical ecology in the European corn borer (ECB, Ostrinia nubilalis Hübner, Lepidoptera: Crambidae): pherotypes reproductive isolation and host plant specialisation.All the experiences were designed to have ecologically relevant information about the chemical signals released or perceived by ECB moth during the reproduction period. Most of the work was conducted close to natural conditions and taking into account all the behavioural traits of ECB.First we investigated what can be the chemical landscape of maize field for host-seeking ECB moth. The whole volatile blends that make up the olfactory environment of maize field biotope was identified according to the ECB oviposition behaviour (Paper I). Secondly taking into account the diel periodicity of ECB behaviour we studied the diel changes of volatile profiles released from maize plant and from maize field (Paper II). Thirdly, we studied the process of host fidelity within the ECB host plants. The volatiles released from different host plants at the time of ECB oviposition flight were identified and the oviposition behaviour was studied in wind tunnel to evidence the host plant preferences of ovipositing females (Paper III). Fourthly, we address the question on assortative mating in ECB pherotypes and we investigated the chemical signals involved in the reproductive isolation in ECB pherotypes. We focused on the male pheromone produced by hairpencils and on courtship behaviour (Paper IV).

The present PhD study investigates the aspect of chemical ecology in the European corn borer (ECB, Ostrinia nubilalis Hübner, Lepidoptera: Crambidae): pherotypes reproductive isolation and host plant specialisation.All the experiences were designed to have ecologically relevant information about the chemical signals released or perceived by ECB moth during the reproduction period. Most of the work was conducted close to natural conditions and taking into account all the behavioural traits of ECB.First we investigated what can be the chemical landscape of maize field for host-seeking ECB moth. The whole volatile blends that make up the olfactory environment of maize field biotope was identified according to the ECB oviposition behaviour (Paper I). Secondly taking into account the diel periodicity of ECB behaviour we studied the diel changes of volatile profiles released from maize plant and from maize field (Paper II). Thirdly, we studied the process of host fidelity within the ECB host plants. The volatiles released from different host plants at the time of ECB oviposition flight were identified and the oviposition behaviour was studied in wind tunnel to evidence the host plant preferences of ovipositing females (Paper III). Fourthly, we address the question on assortative mating in ECB pherotypes and we investigated the chemical signals involved in the reproductive isolation in ECB pherotypes. We focused on the male pheromone produced by hairpencils and on courtship behaviour (Paper IV).

Natural populations exhibit a non-random mating behavior and it is assumed that mate preferences causing the non-random mating behavior play a role in sympatric speciation. In my thesis, I have proposed a new model of a mate preference that is based on ecological performance and I have named it fitness-based mating. Individuals that express this mate preference choose primarily fit partners. Fitness-based mating is modelled for haploid, diallelic populations. Individuals are distributed across two niches, and genomes are simplified to two loci. The first locus is subject to natural selection, and the second-locus genotype gives the strength of the mate preference. The population is separated into females and males, among which only females exhibit the mate preference. Ecological selection acts on both sexes alike. With the model I have investigated how female choosiness based on direct advantages offered by their partners can cause and maintain a polymorphic population. Fitness-based mating is an evolutionary successful mating strategy. It spreads in a population due to its amplifying effect on the reproductive success and on the attractiveness of its carriers. A polymorphism arises naturally in the model. The emergence of a stable polymorphism of traits underlying ecological selection is of special interest, because a polymorphism can be a precursor of speciation.

Orientador: Marcus Aloizio Martinez de Aguiar / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-08-15T21:06:55Z (GMT). No. of bitstreams: 1 Andrade_ElizabethMachadoBaptestini_D.pdf: 4491574 bytes, checksum: 117d970a1c273ecd6ef9533aa742bb0f (MD5) Previous issue date: 2010 / Resumo: Nesse trabalho, estudamos doismecanismos de formação de espécies. No primeiro deles, consideramos um modelo espacial de especiação neutra totalmente probabilístico, sem barreiras geográficas ou interações ecológicas. A população evolui devido a influência de reprodução sexuada, mutações e recombinação. O modelo é baseado em acasalamento seletivo dependente de duas distâncias críticas, uma no espaço físico e outra no espaço dos genomas. Os vínculos introduzidos por essas duas distâncias permitem que a população se divida em grupos reprodutivamente isolados. Nossos resultados mostram que essa dinâmica gera padrões de diversidade consistentes com padrões observados na natureza, como distribuição de abundâncias do tipo log-normal, lei de potência para curvas espécie-área, taxas de especiação e extinção constantes e maior número de espécies para baixas dimensões. No segundo, nós generalizamos um modelo de especiação simpátrica baseado em competição intraespecífica, proposto por Dieckmann e Doebeli. Nesse modelo, uma população assexuada, inicialmente idêntica, evolui por seleção direcional para um fenótipo ótimo, onde a competição intraespecífica induz à seleção disruptiva. Nós mostramos que a forma das funções de competição e distribuição de recursos afetam a probabilidade de dois fenótipos coexistirem. Nós desenvolvemos um modelo analítico e simulações computacionais e comparamos os resultados de ambas abordagens / Abstract: In this work, we have studied two different mechanisms of species formation. In the first one, we considered a probabilistic spatial neutral model of speciation, without physical barriers or any kind of ecological interaction. The population evolves under the combined influences of sexual reproduction, mutation and recombination. The model is based on assortative mating and it depends on two critical distances, one in the genetic space and one in the physical space. The constraints imposed by these two distances allow the population to split in reproductively separated groups. Our results show that this kind of dynamics creates patterns of biodiversity in agreement with observed data, like lognormal distributions of species abundance, power law species-area relationships, steady speciation and extinctions rates and more species in low dimensions. In the second model, we generalized a sympatric speciation model based on intraspecific competition, proposed by Dieckmann and Doebeli. In that model, an assexual population, initially identical, evolves by directional selection to an optimal phenotype, where intraspecific competition induces disruptive selection. We show that the shape of the competition and carrying capacity kernels affects the likelihood of emergence of two coexisting phenotypes. We developed an analytical and a computational model and we compared the results of both approaches / Doutorado / Física da Matéria Condensada / Doutora em Ciências