Ornamental traits in male birds have been the subject of much research effort, and sexual selection is recognized as the leading explanation for their evolution. The expression of ornamental traits in females has received little study until recent decades. Female colouration has been considered a non-adaptive, correlated response to selection on males. However, models predict that male mate choice, female competition, and the evolution of honest signals could help explain female ornamentation, especially where male investment in offspring and variation in female quality are high. I investigated this in the American robin (Turdus migratorius), a socially monogamous species with bi-parental care and variable female ornamentation. Female robins display conspicuous red breast plumage, bright yellow bills, and achromatic ornamentation. Female ornamentation is similar to males, but is subdued to varying degrees across individuals. Female colouration could function as a useful criterion in mate selection by males if it is correlated with aspects of female quality important to producing viable offspring. I assessed whether female ornamentation in robins might act as an honest signal by relating variation in female colour to measures of individual quality and reproductive investment. To assess ornamentation, I took colour measurements of the bill, crown and breast of male and female robins in the field using reflectance spectrometry. Female bill, breast and crown traits reliably predicted age, crown and bill colour traits were related to better body condition, and bill colour decreased seasonally as well as with ectoparasite load. I found evidence of assortative mating based on crown UV reflectance and bill colour. To assess reproductive investment, I measured egg size, yolk proportion, and deposition of yolk testosterone and carotenoids. Females with brighter (lighter) carotenoid-based bill colour laid larger eggs, and females with yellower bills laid eggs with higher yolk proportions and more total yolk carotenoids. Yolk testosterone level was associated with redder female breasts. These results support the hypothesis that female colour may be a reliable indicator of individual quality and capacity for reproductive investment. / Thesis (Master, Biology) -- Queen's University, 2014-01-30 15:09:57.797

Over the past forty years a tremendous number of women have entered the labor market, removing stay-home motherhood as the most dominant female occupation. The linkage between the change in the labor market and change in family structure has drawn a lot of attention from social scientists, and it is on this linkage that this analysis is focused. An essential dimension of this changing behavior is the sharp rise in out-ofwedlock childbearing. The central issue of non-married motherhood is more related to the diminishing willingness to marry than a changing attitude toward fertility. In a setting where individuals choose marriage because of the gains from joint production of child quality as well as the division of labor, the declining gains from specialization for men influence potential spouse selection. Men and women with fewer labor market prospects become less desirable, and consequently a marriage market with more positive assortative mating will be observed. The increase in female labor market participation is larger for highly-educated women but the decrease in marriage rates is more characteristic of less-educated women over this period. What drives these changes can be explained by using a simple economic theory, the fundamental concept of which is that couples with lower labor market prospects also face lower gains from marriage because of the increases in femalemale relative wages in the less-educated and black groups. A narrowing of the gap between male and female wages would reduce the gains from division of labor and lower the incentive to marry. In addition, when the marriage market becomes more positively assorted, low educated men and women are less likely to marry each other. Our empirical results indicate an increase in the homogeneity of wages between spouses over this period regardless of whether we control for education. In particular, black couples are more positively assorted than white couples although the trend converges by the end of the century. We also show that the marriage market is tilted towards better-educated men and women over the period. These findings are consistent with the theory which explains why single motherhood is more concentrated among lesseducated women.

The central goal of human genetics is to understand genetic differences both within and between populations and how these differences contribute to phenotypic variation. Recent advances in genotyping technologies and statistical methodology mean that we can now examine population differences at high genetic resolution, and attempt to find common variants that underlie variation in complex traits in the population. In this thesis, differences in maternal genetic ancestry in Australia were examined and a number of genetic association studies were undertaken in an attempt to map genetic variants that underlie complex traits. Abstract Before presenting the results from the five main genetic analyses, an overview is given of the history of gene-mapping in humans, the challenges this has presented, and the major discoveries from both empirical and theoretical studies that have advanced the field of human genetics to the point where hypothesis-free association testing of common variants with complex traits is now possible. The reasons why mitochondrial DNA has proved so useful in examining the history of populations, and the major findings from the field of mitochondrial population genetics are summarised. In addition, some of the major evidence of a role for mitochondrial variants in complex trait variation is presented. For the first main paper, data from 69 mitochondrial variants that tag the majority of common mitochondrial SNPs in European populations was used to test whether there is evidence for population stratification (i.e. the presence of more than one randomly mating population) in the maternal genetic line of modern Australians. By combining the genetic data with self-reported maternal ancestry data, it was shown that there are significant differences in the patterns of mitochondrial variation between groups of individuals whose maternal ancestors came from different areas of the world. Specifically, it was shown that there are significant differences between groups from different regions of Europe, with those from Eastern Europe showing large differences in SNP and haplogroup frequencies compared to the other groups. A test for assortative mating was performed by comparing whether mates in our sample shared more mitochondrial variants in common when compared to randomly drawn pairs from the population. No evidence of increased sharing was found. The second study involved testing whether common mitochondrial variants are associated with a number of physiological and biochemical traits, the majority of which are risk factors for the metabolic syndrome and type 2 diabetes. Phenotypic and genotypic data was available for just over 2,000 adolescent twins measured at three different timepoints. This is the first known mitochondrial association study to use family data, and a methodology based on a linear model was presented for performing such an association. In spite of having power to detect variants of modest effect, only viii one significant association was found between mt14365 and triacyglycerol levels in twins measured at age 12. This association was not replicated across the other age groups. The third study used the methodology developed for family-based mitochondrial association studies to test for association between mitochondrial variants and a battery of cognitive tests in twins aged 16. A previous study with a small sample size had shown an association between mitochondria and IQ, but this had never been replicated or followed-up. A total of 1,385 individuals from 665 families were included, but no statistically significant associations were found. The most strongly associated SNP was found in a gene in which variants have been shown to influence cognition in mice with a homogeneous nuclear genetic background. For the fourth study, a genome-wide association analysis was carried out of 6 self-reported traits related to the menstrual cycle. Sample sizes ranged from 468 for age at menopause to 5,743 for age at menarche. No SNPs were found to be associated at a genome-wide significant level, however, the results from previous association analyses of age at menarche and age at menopause were replicated. A number of regions for each trait that show modest evidence of association have been identified, and these should be targeted for replication in another sample. In addition, a number of genes that show strong evidence for association with each trait were identified and using a multivariate approach, a SNP in the RNA polymerase III subunit B gene was shown to potentially have a pleiotropic effect on age at menarche and duration of menses. In the final study, a genome-wide association study data for self-reported caffeine consumption and caffeine-related sleep disturbance was performed. A number of loci that potentially influence each trait were identified. The association data was combined with gene expression data from three cell types that had been treated with caffeine. A gene-based test was performed to test whether genes that were found to be consistently up- or down-regulated by caffeine treatment show increased evidence of association. There was no evidence of increased association signals in these genes. A number of the caffeine-regulated genes show strong evidence for overall association and represent good candidate genes for targeted replication in a larger sample. Finally, a synthesis of the main results of each study is presented including potential limitations of this research. This discussion includes a critical assessment of the current findings in both mitochondrial genetics and genome-wide association studies, and potential future directions in the field of gene-mapping in humans.

Despite growing in numbers very quickly in the last half century, interracial marriage remains a disproportionately small segment of all marriages. Much research has been conducted investigating reasons for participation in interracial relationships, and the forces which impede those relationships. Using longitudinal data from the National Longitudinal Study of Adolescent Health (Add Health), I investigated several theories which had previously been researched using data of inferior quality, or only in the context of marriage relationships. I found that macrostructural and contact theories of race relations are supported strongly, and that multiracial identity has a very strong positive effect on the log odds of participation in an interracial relationship. More research is necessary to gain a full sociological understanding of interracial relationship participation as adolescents age and become young adults.

European whitefish (Coregonus lavaretus) forms reproductively isolated sub-populations with different body sizes in the lakes where northern pike (Esox lucius) exists. It has been hypothesized that the initial reproductive isolation between ecotypes arises through size-assortative mate choice or because small and large individuals arrive to the spawning grounds at different times. To test these hypotheses, I caught and measured both breeding whitefish pairs and singular whitefish on the spawning grounds over the spawning season. There was no correlation between the lengths of males and females in breeding pairs, indicating that mate selection was random with respect to body size. There were no significant differences in body length between sampling dates during the field period in November 2021, suggesting that there is no divergence in spawning time between large and small individuals. Thus, neither of the two hypotheses were supported. Interestingly, males have significantly higher amount of breeding tubercles than females according to my results, which could be a selective factor in mate selection. However, the function of the tubercles is yet poorly understood.

The dissertation explores recent trends in educational assortative mating in Western countries. In particular, the rise of hypogamy is analyzed, focusing on its causes and consequences. The dissertation aims at providing new evidence on issues concerning the rise of hypogamy at the individual level. As for its causes, changes in the partner market composition are analyzed in a life course perspective as a possible driver of hypogamy, underlining the dynamic nature of its role during the partner search. Moreover, elements from the social psychology field such as the activation of behaviors to find a partner are analyzed. Finally, the dissertation studies how partner choice shapes processes of social reproduction, and in particular educational reproduction. A penalty for hypogamy is found among higher educated women, but it does not persist across generations. The dissertation provides two main contributions to the literature. First, it provides evidence of the relevance of adopting a life-course approach when looking at dynamics of union formation, and in particular hypogamy. Second, it provides evidence of the importance of partner choice for social reproduction processes, especially among women.

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.

The thesis consists of a summary and four self-contained papers. Paper [I] examines the effects of interregional migration on gross earnings in married and cohabiting couples. In particular, we examine the link between education level and income gains. We find that pre-migration education level is a key determinant of migration and economic outcomes and is also a determinant of the effect of migration on income distribution within the household. The positive average effect on household earnings is largely explained by income gains among highly-educated males. Females generally experience no significant income gain from migration in absolute terms. Paper [II] analyzes the effect of the spouse’s education on individual earnings. In this study, we control for time-invariant heterogeneity that may be correlated with the spouse’s education level and use a rich data set that includes observations of individuals when they are single and when they are married. The results support the hypothesis of cross-productivity for both males and females. Furthermore, couples with education within the same field experience even larger effects. In Paper [III] we aim to study how the spouse’s productivity in the labor market affects one’s own individual earnings when married. Using longitudinal data on individuals as both single and married allows us to estimate the spouses’ productivity as single persons and thereby avoid problems of endogeneity between the two spouses’ labor market performances. Productivity is approximated with residuals from estimates of pre-marriage earnings equations. Results indicate that there are negative effects of the spouse’s productivity on individual earnings for both males and females, and that this effect appears to be enhanced by the duration of the marriage. Paper [IV] studies spousal matching on earnings for females in secondorder marriages. We aim to follow women who marry, divorce, and subsequently remarry compared with females who marry and stay married over the course of the study interval. Overall, we find significant positive correlations for all three of the marital partitions. The correlation tends to be smaller for the first of a sequence of marriages for women who divorce than for women who marry and stay so. For the second of the successive marriages, however, the correlation of the residuals is larger than that for women who marry but once.

The bounded-hybrid superiority hypothesis (BHSH) predicts stable hybrid zones are characterized by hybrids having the highest fitness within the zone. The dynamic-equilibrium hypothesis (DEH) predicts hybrids to have the lowest fitness and mating should be strongly assortative in the hybrid zone. I used phenotypic-based hybrid indices (HI) to assess mating patterns, reproductive success, and survival of hybridizing northern flickers (Colaptes auratus) within the hybrid zone at Riske Creek, British Columbia. Contrary to the BHSH, flickers showed significant assortative pairing (P = 0.038) which may result via passive mate choice if yellow and red flickers migrate from allopatric winter ranges. North American band recoveries show red-shafted and yellow-shafted flickers winter on different sides of the Rocky Mountains while red-orange hybrids from Riske Creek winter in the range of red-shafted flickers. Arrival dates of phenotypes did not support the idea that mating patterns are caused passively via different arrival schedules. However, assortative mating patterns did correlate with regional weather patterns along flicker migration routes as well as the North Atlantic Oscillation (NAO) a continental weather pattern that has been shown to influence various aspects of the annual cycle in other birds. If variable weather patterns result in different mating patterns by affecting migration, the geographic location of the northern portion of the zone may be variable due to the migratory behaviour of individuals.<p>There were no differences among yellow, orange and red flickers to win more agonistic contests or have earlier nest initiation dates, larger clutch sizes, greater hatching success, or produce more fledglings. No colour group had a higher likelihood of having a successful compared to a depredated nesting attempt. Aggression was similar between red (N = 21) and yellow flickers (N = 20) during taxidermy model presentations of pure red-shafted and yellow-shafted flickers. Using Akaikes information criterion (AIC) in Program MARK, I determined survival was best modeled as either constant between males and females or varying annually according to weather. Models incorporating HI had less support but suggested that survival is best modeled as a linear relationship where red-shafted flickers have the highest survival. Survival modeled in quadratic relationships found hybrid flickers to have the highest apparent survival estimates in support of the BHSH. Overall there was no support for reduced hybrid fitness, but survival appears to be influenced more by annual variation rather than strictly by an individuals HI. Overall, I failed to find reduced hybrid fitness in support of the DEH but also failed to find increased hybrid fitness as predicted by the BHSH. Annual changes in selection pressure could prevent introgression of hybrid genes throughout the zone if selection favours red-shafted genes in some years and yellow-shafted genes in other years.