We set up a trade model with heterogeneous firms and a worker population that is heterogeneous in two dimensions: workers are either skilled or unskilled, and within each skill category there is a continuum of abilities. Workers with high abilities, both skilled and unskilled, are matched to firms with high productivities, and this leads to wage differentials within each skill category across firms. Self-selection of the most productive firms into exporting generates an exporter wage premium, and our framework with skilled and unskilled workers allows us to decompose this premium into its skill-specific components. We employ linked employer-employee data from Germany to structurally estimate the parameters of the model. Using these parameter estimates, we compute an average exporter wage premium of 5 percent. The decomposition by skill turns out to be quantitatively highly relevant, with exporting firms paying no wage premium at all to their unskilled workers, while the premium for skilled workers is 12 percent.

Educational assortative mating and earnings inequality has both increased in both Europe and the United States in the last decades. As a result, educational assortative mating, or educational homogamy, has been suggested as a potential explanation for the increase in earnings inequality. According to this hypothesis increased sorting on education will lead to polarization between lower and higher-educated couples where the advantages of the latter will compound on one another and lead to increased economic inequality.   The majority of the studies to date report a non-relationship between educational assortative mating and earnings inequality, one of the exceptions being a study of Denmark. This exception has led sociologists to theorize that the impact of educational assortative mating could be especially strong in the Nordic countries. In this study I test this hypothesis by employing a novel decomposition method, the Theil-index, to answer if increases in educational assortative mating are associated with increases in earnings inequality in Sweden between 2000 and 2010, using data from the Standard of Living Survey (LNU).   The result is a non-relationship between homogamy and earnings inequality and an overall decrease in earnings inequality in the sample. The result is another null result for the hypothesis that educational homogamy leads to inequality, and points to a larger discrepancy between singles and couples than between couples. If corroborated, this decrease in earnings inequality would mean a divergence, in earnings inequality, between partnered individuals and the general population. Future studies should focus on the extent of this divergence.

Assortative Mating, the tendency for mate selection to occur on the basis of similar traits, plays an essential role in understanding the genetic variation on academic achievements and intelligence (IQ). It is an important mechanism explaining spousal concordance. We used principal component analysis (PCA) for spousal correlation. There is a significant positive correlation between spouses by the new variable PC1 (correlation coefficient=0.515, p<0.0001). We further research the genetic factor that affects IQ by using the same data. We performed a low density genome-wide association (GWA) analysis with a family-based association test to identify genetic variants that associated with intelligence as measured by WAIS full-score IQ (FSIQ). NTM at 11q25 (rs411280, p=0.000764) and NR3C2 at 4q31.23 (rs3846329, p=0.000675) were 2 novel genes that haven't been associated with IQ from other studies. This study may serve as a resource for replication in other populations and a foundation for future investigations.

This dissertation focuses on studying various network formation games in Economics. We explore a different model in each chapter to capture various aspects of networks. Chapter 1provides an overview of this dissertation. Chapter 2 studies the possible Nash equilibrium configurations in a model of signed network formation as proposed by Hiller (2017). We specify the Nash equilibria in the case of heterogeneous agents. We find 3 possible Nash equilibrium configurations: Utopia network, positive assortative matching, and disassortative matching. We derive the specific conditions under which they arise in a Nash equilibrium. In Chapter 3, we study a generalized model of signed network formation game where the players can choose not only positive and negative links but also neutral links. We check whether the results of the signed network formation model in the literature still hold in our generalized framework using the notion of pairwise Nash equilibrium. Chapter 4 studies inequality in a weighted network formation model using the notion of Nash equilibrium. As a factor of inequality, there are two types of players: Rich players and poor players. We show that both rich and poor players designate other rich players as their best friends. As a result, We present that nested split graphs are drawn from survey data because researchers tend to ask respondents to list only a few friends. / Doctor of Philosophy / This dissertation focuses on studying various network formation games in Economics. We explore a different model in each chapter to capture various aspects of networks. Chapter 1 provides an overview of this dissertation. Chapter 2 studies the possible singed network configurations in equilibrium. In the signed network, players can choose a positive (+) relationship or a negative (-) relationship toward each other player. We study the case that the players are heterogeneous. We find 3 possible categories of networks in equilibrium: Utopia network, positive assortative matching, and disassortative matching. We derive the specific conditions under which they arise in equilibrium. In Chapter 3, we study a generalized model of signed network formation game where the players can choose not only positive and negative links but also neutral links. We check whether the results of the signed network formation model in the literature still hold in our generalized framework. Chapter 4 studies inequality in a weighted network formation model using the notion of Nash equilibrium. In this weighted network model, each player can choose the level of relationship. As a factor of inequality, there are two types of players: rich players and poor players. We show that both rich and poor players choose other rich players as their best friends. As a result, we present that nested split graphs are drawn from survey data because these social network data are censored due to the limit of the number of responses.

En raison des forts coûts en temps et en énergie associés à chaque reproduction, les femelles ne sont généralement pas aussi disponibles que les mâles pour se reproduire. Les mâles entrent donc souvent en compétition pour accéder aux femelles disponibles. Ceci conduit à une forte sélection sexuelle chez les mâles. Un des exemples les plus frappants de compétition entre mâles peut être observé chez certaines espèces de crustacés chez qui les femelles ne sont sexuellement réceptives que pour un temps très limité. Les mâles ont donc évolué une stratégie de gardiennage précopulatoire grâce à laquelle ils monopolisent une femelle plusieurs jours avant qu’elle ne devienne réceptive. Ce comportement mâle est lui-même coûteux en temps et en énergie. En conséquence, il a été suggéré que les mâles devraient devenir sélectifs envers les femelles du fait du fort investissement que chaque reproduction représente pour eux. A l’aide d’un modèle mathématique, nous prédisons que les mâles effectuant de longs gardiennages précopulatoires devraient préférer s’apparier avec les grandes femelles plus fécondes. Toutefois, cette sélectivité devrait rester faible du fait de la forte compétition pour accéder aux femelles libres. Nous suggérons plutôt que les mâles devraient chercher à s’apparier avec des femelles de bonne qualité après s’être initialement apparié avec une femelle. Quand les mâles en couple rencontrent une femelle libre de meilleure qualité que leur propre femelle, ils devraient quitter leur femelle pour s’accoupler avec la nouvelle femelle. Contrairement à cette prédiction, nos expériences ont montré que les mâles en couple d’un crustacé amphipode Gammarus pulex ne changeaient pas systématiquement de femelle quand nous leurs proposions une femelle de meilleure qualité que leur propre femelle. Ils décidaient de changer de partenaire uniquement quand leur femelle était de mauvaise qualité, indépendamment de la qualité de la nouvelle femelle libre. D’autres expériences sont nécessaires pour comprendre le caractère adaptatif de ce comportement de changement de partenaire, seulement basé sur une partie de l’information disponible. Ces deux études soulignent la difficulté d’inférer des patrons de reproduction uniquement à partir des préférences individuelles. Dans la première étude, les mâles étaient contraints par la compétition pour accéder aux femelles libres. Dans la seconde, le processus de prise de décision des mâles conduisait à un comportement de choix apparemment sous-optimal. Ces contraintes n’ont que rarement été prises en compte malgré leur grande importance lorsqu’il s’agit de comprendre les causes comportementales d’un patron de reproduction très répandus chez les crustacés à gardiennage précopulatoire : l’homogamie pour la taille. Il a principalement été suggéré que ce patron de reproduction était issu d’une préférence mâle pour les grandes femelles associée à un avantage des grands mâles pour accéder aux femelles. Cette hypothèse n’a malgré tout reçu que peu de support empirique. A l’aide d’un modèle par simulation individu centrée, nous avons donc testé l’hypothèse selon laquelle une préférence mâle pour la distance à la mue des femelles serait à l’origine de l’homogamie pour la taille chez les crustacés à gardiennage précopulatoire. Quand les mâles préfèrent s’apparier avec des femelles qui sont strictement plus proches de la mue qu’eux, les couples formaient un patron d’homogamie pour la taille. Puisque plusieurs préférences différentes peuvent conduire à un même patron de reproduction, ce résultat souligne l’importance de considérer le processus complet de mise en couple pour étudier le lien entre les préférences individuelles et les patrons de reproduction. Les stratégies de femelles peuvent aussi jouer un rôle important dans les processus de mise en couple. Contrairement aux mâles, les femelles ont été décrites comme préférant les gardiennages courts du fait des coûts associés à la mise en couple. / Because of strong costs associated with each mating event, females are usually not as available for reproduction as males at any given time. Males are therefore in competition with each other for access to receptive females, hence leading to strong sexual selection. One textbook case of such a mating system occurs in moulting crustaceans where females can only be fertilized during a short period following their moult. This has favoured the evolution male strategies to monopolize females before their period of receptivity. Such a precopulatory mate guarding is widespread among many taxa and represents one of the most striking example of males’ competitive traits favoured by sexual selection. However, recent investigations have suggested that because males’ sexually selected traits often involve opportunity or mortality costs, males should become choosy towards females. Using a theoretical approach, we showed that males performing long lasting mate guarding should choose larger, more fecund females. However, under sequential encounter of potential mates, competition for female access decreases male choosiness before entering in precopula. We rather suggest that males should become choosy after initial pairing with a female. When encountering an unpaired female of better quality than their current female, paired males should switch partners. Contrary to our expectations, even under simultaneous encounters of two females, males did not seem to assess their relative quality. Instead they decided to change partner when their own female was of low absolute quality. This led to several cases where males forewent the possibility of increasing their fitness. Further investigations are needed to understand the adaptive significance of using only a subset of information in decision making. These two cases highlight the difficulty of inferring mating patterns from mating preferences only. In the first case, male preference was constrained by competition for access to females while in the second one, sampling processes led to apparent suboptimal mate choices. These potential constraints on decision making have rarely been acknowledge in precopulatory mate guarding crustaceans in spite of their major importance when inferring the causes of a well-known pairing pattern occurring in these species: size-assortative pairing. Size assortment among pairs has mainly been considered to come from a male directional preference for larger females associated with a large male advantage in getting access to preferred females. However, this hypothesis has received contrasted empirical support and little is known about the underlying pairing process causing size-assortative pairing. We investigated theoretically the possibility that a state-dependent male mating preference could account for size-assortative pairing. When males chose females which were exclusively closer to moult than them, assortative pairing by size arose under strong male-male competition. Because several preferences can account for a given pattern, this result emphasises the importance of considering the whole pairing process when studying the link between preferences and mate choice. Female strategies may also be of great importance during the pairing process. Contrary to males, females have been suggested to prefer short precopulatory mate guarding due to costs associated with pairing. Such a sexual conflict over guarding duration may have major effects on co-evolutionary dynamics between males and females traits. Proving its occurrence is yet challenging because empirical studies often lack a full economical survey of costs and benefits for females associated with male traits. Females benefits associated with long lasting precopulatory mate guarding have particularly been overlooked in previous studies. Here, we proposed several potential benefits for females and discuss their influence on sexual conflict over guarding duration.

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

Human mate choice is far from random. Assortative mating can be either positive (homogamy), when people prefer and choose partners with self-similar characteristics, or negative (heterogamy, complementarity), when people prefer self-dissimilar partners. Over one hundred years of research, it has been shown that people generally couple based on the principle of homogamy. This thesis seeks to address the following two goals. First, it critically reviews the current state of knowledge in positive assortative mating (in particular, empirical support, factors affecting homogamy, mechanisms of homogamy, relationship and genetic impact of homogamy, and methodological pitfalls of research). This section includes theoretical papers deal with further mechanisms of assortative mating (homogamy, imprinting-like effect, heterogamy, complementarity). Second, the thesis provides further test of assortative mating in 'ideal partners' (preferences) and actual partners, in the context of sex, sexual orientation (heterosexual and non-heterosexual), and population (Brazil and Czech Republic). Results of these studies show that the principle of homogamy is valid irrespective of sex and population. However, they find a stronger tendency for homogamy in actual partners among heterosexuals than in homosexuals, although...

We set up a trade model with heterogeneous firms and a worker population that is heterogeneous in two dimensions: workers are either skilled or unskilled, and within each skill category there is a continuum of abilities. Workers with high abilities, both skilled and unskilled, are matched to firms with high productivities, and this leads to wage differentials within each skill category across firms. Self-selection of the most productive firms into exporting generates an exporter wage premium, and our framework with skilled and unskilled workers allows us to decompose this premium into its skill-specific components. We employ linked employer-employee data from Germany to structurally estimate the parameters of the model. Using these parameter estimates, we compute an average exporter wage premium of 5 percent. The decomposition by skill turns out to be quantitatively highly relevant, with exporting firms paying no wage premium at all to their unskilled workers, while the premium for skilled workers is 12 percent.

Plants often occur aggregated into clusters and this spatial pattern is supposed to affect pollinator behaviour and pollen dispersal. Such pollinator reaction may influence reproductive success of zoogamous plant species both in terms of number of available mates and their genetic diversity (nearby growing plant individuals are also often closely related, especially in clonal plants). In the present thesis, I investigated the influence of plant spatial aggregation on pollinator behaviour and how this translates into pollen transfer. For that purpose, I carried three experiments. In the Experiment 1, I used potted plants placed into arrays and aggregated into four patches in order to track the pollen dispersal by means of a UV-dye pollen analogue. I manipulated distances between plants within clusters (dense × loose) and between clusters (near × far). I conducted this experiment for three plant species differing in their pollinator spectra. In the Experiment 2, I observed pollinator foraging sequences (sequences of visited plant individuals) under the same experimental design as for the first experiment, but I carried out this experiment for five plant species. In addition in one study species, Dianthus carthusianorum, I conducted the Experiment 3 to get better insight into pollination effectiveness...