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Background: Hypertension, a critical risk factor for cardiovascular diseases, is found to cluster between spouses due to within-couple aggregation of antecedent environmental risk factors, either through assortative mating or cohabitation. However, majority of the evidence of spousal concordance of hypertension is from Caucasoid couples from western societies, whereas marriage, partner selection, and post-marital roles of husband and wives are very different in Indian society. Therefore, we aimed to comprehensively examine the phenomenon of spousal concordance of hypertension in Indian couples. Method: Couples from Longitudinal Ageing Study in India Wave 1 (n = 10,994) and National Family Health Survey Round 5 (n = 52,026) represented 15 years + Indian spouses. Hypertension was defined when systolic and/or diastolic blood pressure was > 139 and > 89 mmHg respectively, and/or if the individual was previously diagnosed or on anti-hypertensive medication. Odds Ratios (OR) estimated the within-couple concordance of hypertension while adjusting for five environmental risk factors of hypertension: individual-level body mass index, education and caste, and household-level wealth and place of residence. Result: OR marginally attenuated from 1.84 (95% Confidence Interval: 1.77, 1.92) to 1.75 (1.68, 1.83) after adjustment, signifying negligible explanation by environmental risk factors, and plausibility of "novel" risk factors. Concordance continued to weaken with age (OR: 2.25 (2.02, 2.52) in < 30 versus 1.36 (1.20, 1.53) in ≥ 60 years). Conclusion: Our study underscores two critical knowledge gaps: first, the identity of "novel" risk factors of hypertension and second, the mechanism behind weakening of concordance with age. Future research should explore these novel risk factors rigorously and try to modify them. Also, primary healthcare policy of the country should focus on couples in addition to individuals for hypertension and cardiovascular disease screening and management. [ABSTRACT FROM AUTHOR]

Measurement error in polygenic indices (PGIs) attenuates the estimation of their effects in regression models. We analyze and compare two approaches addressing this attenuation bias: Obviously Related Instrumental Variables (ORIV) and the PGI Repository Correction (PGI-RC). Through simulations, we show that the PGI-RC performs slightly better than ORIV, unless the prediction sample is very small (N < 1000) or when there is considerable assortative mating. Within families, ORIV is the best choice since the PGI-RC correction factor is generally not available. We verify the empirical validity of the simulations by predicting educational attainment and height in a sample of siblings from the UK Biobank. We show that applying ORIV between families increases the standardized effect of the PGI by 12% (height) and by 22% (educational attainment) compared to a meta-analysis-based PGI, yet estimates remain slightly below the PGI-RC estimates. Furthermore, within-family ORIV regression provides the tightest lower bound for the direct genetic effect, increasing the lower bound for the standardized direct genetic effect on educational attainment from 0.14 to 0.18 (+29%), and for height from 0.54 to 0.61 (+13%) compared to a meta-analysis-based PGI. Measurement error in polygenic indices attenuates their power to predict complex traits. Here, the authors compare two approaches addressing this attenuation bias and provide guidance on which approach to apply in various scenarios. [ABSTRACT FROM AUTHOR]

Estimates of shared environmental influence on educational attainment (EA) using the Classical Twin Design (CTD) have been enlisted as genetically sensitive measures of unequal opportunity. However, key assumptions of the CTD appear violated for EA. In this study we compared CTD estimates of shared environmental influence on EA with estimates from a Nuclear Twin and Family Design (NTFD) in the same 982 German families. Our CTD model estimated shared environmental influence at 43%. After accounting for assortative mating, our best fitting NTFD model estimated shared environmental influence at 26%, disaggregating this into twin-specific shared environments (16%) and environmental influences shared by all siblings (10%). Only the sibling shared environment captures environmental influences that reliably differ between families, suggesting the CTD substantially overestimates between-family differences in educational opportunity. Moreover, parental education was found to have no environmental effect on offspring education once genetic influences were accounted for. [ABSTRACT FROM AUTHOR]

A lineage of 422,374 English people (1600 to 2022) contains correlations in social outcomes among relatives as distant as 4th cousins. These correlations show striking patterns. The first is the strong persistence of social status across family trees. Correlations decline by a factor of only 0.79 across each generation. Even fourth cousins, with a common ancestor only five generations earlier, show significant status correlations. The second remarkable feature is that the decline in correlation with genetic distance in the lineage is unchanged from 1600 to 2022. Vast social changes in England between 1600 and 2022 would have been expected to increase social mobility. Yet people in 2022 remain correlated in outcomes with their lineage relatives in exactly the same way as in preindustrial England. The third surprising feature is that the correlations parallel those of a simple model of additive genetic determination of status, with a genetic correlation in marriage of 0.57. [ABSTRACT FROM AUTHOR]

Using a new database of 1.7 million marriage records for England 1837-2021 we estimate assortment by occupational status in marriage, and the intergenerational correlation of occupational status. We find the underlying correlations of status groom-bride, and father-son, are remarkably high: 0.8 and 0.9 respectively. These correlations are unchanged 1837-2021. There is evidence this strong matching extends back to at least 1754. Even before formal education and occupations for women, grooms and brides matched tightly on educational and occupational abilities. We show further that women contributed as much as men to important child outcomes. This implies strong marital sorting substantially increased the variance of social abilities in England. Pre-industrial marital systems typically involved much less marital sorting. Thus the development of assortative marriage may play a role in the location and timing of the Industrial Revolution, through its effect on the supply of those with upper-tail abilities. [ABSTRACT FROM AUTHOR]

After establishing secondary contact, recently diverged populations may remain reproductively isolated or may hybridize to a varying extent depending on factors such as hybrid fitness and the strength of assortative mating. Here, we used genomic and phenotypic data from three independent contact zones between subspecies of the variable seedeater (Sporophila corvina) to examine how coloration and genetic divergence shape patterns of hybridization. We found that differences in plumage coloration are probably maintained by divergent selection across contact zones; however, the degree of plumage differentiation does not match overall patterns of hybridization. Across two parallel contact zones between populations with divergent phenotypes (entirely black vs. pied plumage), populations hybridized extensively across one contact zone but not the other, suggesting that plumage divergence is not sufficient to maintain reproductive isolation. Where subspecies hybridized, hybrid zones were wide and formed by later‐generation hybrids, suggesting frequent reproduction and high survivorship for hybrid individuals. Moreover, contemporary gene flow has played an important role in shaping patterns of genetic structure between populations. Replicated contact zones between hybridizing taxa offer a unique opportunity to explore how different factors interact to shape patterns of hybridization. Overall, our results demonstrate that divergence in plumage coloration is important in reducing gene flow but insufficient in maintaining reproductive isolation in this clade, and that other factors such as divergence in song and time since secondary contact may also play an important role in driving patterns of reduced hybridization and gene flow. [ABSTRACT FROM AUTHOR]

Previous theory has shown that assortative mating for plastic traits can maintain genetic divergence across environmental gradients despite high gene flow. Yet these models did not examine how assortative mating affects the evolution of plasticity. We here describe patterns of genetic variation across elevation for plasticity in a trait under assortative mating, using multiple-year observations of budburst date in a common garden of sessile oaks. Despite high gene flow, we found significant spatial genetic divergence for the intercept, but not for the slope, of reaction norms to temperature. We then used individual-based simulations, where both the slope and the intercept of the reaction norm evolve, to examine how assortative mating affects the evolution of plasticity, varying the intensity and distance of gene flow. Our model predicts the evolution of either suboptimal plasticity (reaction norms with a slope shallower than optimal) or hyperplasticity (slopes steeper than optimal) in the presence of assortative mating when optimal plasticity would evolve under random mating. Furthermore, a cogradient pattern of genetic divergence for the intercept of the reaction norm (where plastic and genetic effects are in the same direction) always evolves in simulations with assortative mating, consistent with our observations in the studied oak populations. [ABSTRACT FROM AUTHOR]

Mate choice is a key process in animals to optimize the fitness benefits of reproduction, and it is generally guided by phenotypic features of potential partners that mirror reproductive abilities. Assortative mating occurs when there is within-pair selection for specific functional traits that can confer fitness benefits. Assortative mating can be positive if mates are more similar, and negative if they are more dissimilar than expected by chance. Mate choice is particularly important in long-lived species with biparental care, such as procellariforms that form long term monogamous bonds. We assessed the mating strategy of a sexually dimorphic Mediterranean procellariform, the Scopoli's Shearwater (Calonectris diomedea), by testing for assortative mating according to bill (in accordance with previous studies on a sister species) and tarsus size (proxy of body size). We found that shearwaters adopted a positive size-assortative mating by tarsus length, while mating for bill size was random. Moreover, tarsus length was positively correlated with the duration of incubation shifts, when individuals are fasting on eggs. The observed assortative mating could be the results of choice by similarity between individuals, likely because partners with similar relative size have similar tolerance to fasting. Alternatively, the observed pattern could be the product of mutual mate choice, with a selection for large size that could confer competitive abilities in nest selection, defense, foraging aggregations and fasting ability. While our data suggest strong assortative mating in the Scopoli's Shearwater (R = 0.4), we cannot fully disentangle the multiple processes at play acting on mate choice. [ABSTRACT FROM AUTHOR]

Few studies have followed immigrant-origin individuals from adolescence to adulthood or examined their spousal choices. Using longitudinal data from Add Health, we present a life-course model that examines the differences in racial assortative mating between children of immigrants and non-immigrants. The results reveal substantial variation in racial endogamy from generation to generation. Racial endogamy was highest in the third generation, but this is due entirely to high racial endogamy among whites. Out-marriage was most pronounced among first- and second-generation immigrants. Our life-course approach shows that the effects of race and generation on intermarriage were mediated by family background (e.g. language proficiency and residence) and educational attainment (at time of marriage), a finding largely indicative of processes of marital assimilation that unfold over time and generation. Evidence of acculturation and structural assimilation, however, could not fully account for the large, persistent, and uneven effects of race and generation on interracial marriage. [ABSTRACT FROM AUTHOR]

Partners resemble each other in health behaviors and outcomes such as alcohol use, smoking, physical activity, and obesity. While this is consistent with social contagion theory suggesting partner influence, it is notoriously difficult to establish causality because of assortative mating and contextual confounding. We offer a novel approach to studying social contagion in health in long-term partnerships by combining genetic data of both partners in married/cohabiting couples with longitudinal data on their health behaviors and outcomes. We examine the influence of the partner's genetic predisposition for three health outcomes and behaviors (BMI, smoking, and drinking) among married/cohabiting couples. We use longitudinal data from the Health and Retirement Study and the English Longitudinal Study of Ageing with data on health outcomes and genotypes for both partners. Results show that changes over time in BMI, smoking, and drinking depend on the partner's genetic predispositions to these traits. These findings underline the importance of people's social surroundings for their health and highlight the potential of targeting health interventions at couples. [ABSTRACT FROM AUTHOR]

We analyze the long-run and intergenerational effects of a large-scale school building project (INPRES) that took place in Indonesia between 1974 and 1979. Specifically, we link the geographic rollout of INPRES to longitudinal data from the Indonesian Family Life Survey covering two generations. We find that individuals exposed to the program have better health later in life along multiple measures. We also find that the children of those exposed experience improved health and educational outcomes and that these effects are generally stronger for maternal exposure than paternal exposure. We find some evidence that household resources, neighborhood quality, and assortative mating may explain a portion of our results. Our findings highlight the importance of considering the long-run and multigenerational benefits when evaluating the costs and benefits of social interventions in a middle-income country. [ABSTRACT FROM AUTHOR]

Cooperative species have provided extensive evidence on the evolution of cooperation and kin selection mechanisms, but they have been poorly studied in terms of sexual selection. Assortative mating has been recorded in several taxonomic groups and has significant implications for population genetics. In this study, we investigated the occurrence of sex differences, assortative mating, and the relationship between ornaments and fitness in the campo flicker (Colaptes campestris campestris). Campo flickers are facultative cooperative breeders with a complex social and reproductive system. Both males and females are ornamented in the species. Our results demonstrate that males and females are almost entirely alike, and that they mate assortatively for neck and throat coloration. Moreover, individuals possessing larger crowns and a lighter yellow neck coloration were more likely to reproduce. Surprisingly, more homozygous individuals were also more likely to reproduce. Our results support at least two possibilities. The first possibility is that same-sex competition within and between social units may be intense and likely to influence territory occupation, within-group hierarchy, and, ultimately, reproductive success. Alternatively, variation in reproductive success may be associated with mutual sex preferences. The association between fitness and lower heterozygosity may be related to some level of inbreeding, although it does not seem to be impacting campo flicker population numbers. Significance statement: In this study, we investigated the extent to which morphometric traits and plumage coloration predict sex, body condition, and breeding probability in the facultative cooperative breeder Campo Flicker (Colaptes campestris campestris). Our results showed that only body mass differed significantly between males and females, with males being heavier. Males and females are almost entirely alike in terms of coloration. Interestingly, we found that larger crowns and a lighter yellow neck coloration were positively associated with breeding probability, while heterozygosity was negatively associated. These findings advance our understanding of the role of sexual selection in cooperative breeders and provide valuable insights into the impact of competition and mate preferences in ornament evolution and population genetics of social species. [ABSTRACT FROM AUTHOR]

Quantifying gene flow between lineages at different stages of the speciation continuum is central to understanding speciation. Heliconius butterflies have undergone an adaptive radiation in wing color patterns driven partly by natural selection for local mimicry. Color patterns are also known to be used as assortative mating cues. Therefore, wing pattern divergence is considered to play a role in speciation. A corollary is that mimicry between closely related species may be associated with hybridization and interfere with reproductive isolation. Here, we take a multifaceted approach to explore speciation history, species boundaries, and traits involved in species differentiation between the two closely related species, Heliconius hecale and Heliconius ismenius. We focus on geographic regions where the two species mimic each other and contrast this with geographic regions where they do not mimic each other. To examine population history and patterns of gene flow, we tested and compared a four-population model accounting for linked selection. This model suggests that the two species have remained isolated for a large part of their history, yet with a small amount of gene exchange. Accordingly, signatures of genomic introgression were small except at a major wing pattern allele and chemosensing genes and stronger in the mimetic populations compared with nonmimetic populations. Behavioral assays confirm that visual confusion exists but that short-range cues determine strong sexual isolation. Tests for chemical differentiation between species identified major differences in putative pheromones which likely mediate mate choice and the maintenance of species differences. [ABSTRACT FROM AUTHOR]

Introduction: Assortative mating refers describes a phenomenon in which individuals with similar phenotypic traits are more likely to mate and reproduce with each other; i.e. assortative mating occurs when individuals choose partners based on their similarity or dissimilarity in certain traits. to patterns of non-randommating of spouses leading to phenotypic resemblance. There are various theories about the its underlying mechanisms, which have different genetic consequences. Methods: Weanalyzed examined two possible mechanisms underlying assortative mating - phenotypic assortment and social homogamy - for educational attainment in two countries utilizing data of mono- and dizygotic twins and their spouses (1,451 Finnish and 1,616 Dutch twin-spouse pairs). Results: The spousal correlations were 0.51 in Finland and 0.45 in the Netherlands, to which phenotypic assortment contributed 0.35 and 0.30, and social homogamy 0.16 and 0.15, respectively. Conclusion: Both social homogamy and phenotypic assortment are important processes in spouse selection in Finland and the Netherlands. In both countries, phenotypic assortment contributes to a greater degree to the similarity of spouses than social homogamy. [ABSTRACT FROM AUTHOR]

Background: Genomic selection involves choosing as parents those elite individuals with the higher genomic estimated breeding values (GEBV) to accelerate the speed of genetic improvement in domestic animals. But after multi-generation selection, the rate of inbreeding and the occurrence of homozygous harmful alleles might increase, which would reduce performance and genetic diversity. To mitigate the above problems, we can utilize genomic mating (GM) based upon optimal mate allocation to construct the best genotypic combinations in the next generation. In this study, we used stochastic simulation to investigate the impact of various factors on the efficiencies of GM to optimize pairing combinations after genomic selection of candidates in a pig population. These factors included: the algorithm used to derive inbreeding coefficients; the trait heritability (0.1, 0.3 or 0.5); the kind of GM scheme (focused average GEBV or inbreeding); the approach for computing the genomic relationship matrix (by SNP or runs of homozygosity (ROH)). The outcomes were compared to three traditional mating schemes (random, positive assortative or negative assortative matings). In addition, the performance of the GM approach was tested on real datasets obtained from a Large White pig breeding population. Results: Genomic mating outperforms other approaches in limiting the inbreeding accumulation for the same expected genetic gain. The use of ROH-based genealogical relatedness in GM achieved faster genetic gains than using relatedness based on individual SNPs. The GROH-based GM schemes with the maximum genetic gain resulted in 0.9%–2.6% higher rates of genetic gain ΔG, and 13%–83.3% lower ΔF than positive assortative mating regardless of heritability. The rates of inbreeding were always the fastest with positive assortative mating. Results from a purebred Large White pig population, confirmed that GM with ROH-based GRM was more efficient than traditional mating schemes. Conclusion: Compared with traditional mating schemes, genomic mating can not only achieve sustainable genetic progress but also effectively control the rates of inbreeding accumulation in the population. Our findings demonstrated that breeders should consider using genomic mating for genetic improvement of pigs. [ABSTRACT FROM AUTHOR]

We use census microdata for Spain and the United States to examine gender differences in cross‐national heterosexual couples (marriages and cohabitating unions involving natives and immigrant spouses). We examine whether native men and native women in cross‐national couples exhibit similar patterns regarding the country of birth, age, and educational attainment of their international partners. Countries are ranked by their level of the human development index (HDI). In both Spain and the United States, native men are slightly overrepresented in cross‐national couples. Native men are more likely to be married to individuals from low HDI countries than native women. On the contrary, native women are predominantly married to men born in countries with similar or higher levels of HDI. Unions of native men are characterized by large spousal age differences, which increase with the HDI gap; this pattern reverses among native women. These gender asymmetries do not extend to education level, with cross‐national couples, overall, involving highly educated individuals. These results point to the endurance of certain features of traditional marriage patterns in cross‐national couples, but the patterns differ starkly between native men and native women. [ABSTRACT FROM AUTHOR]

This study examines the degree of educational assortative mating, its evolution, and its relationship with income inequality in Thailand using national labor force survey data from 1985 to 2016. Since the 1990s, Thailand shows a trend of decreasing educational homogamy, but there is evidence of continuing educational hypergamy in Thai households. Using the semiparametric decomposition method of DiNardo, Fortin and Lemieux (1996), the study finds that educational assortative mating has affected changes in household income inequality over time. Furthermore, there exists a negative relationship between income inequality and marital sorting with same education, which contradicts evidence found in developed countries. [ABSTRACT FROM AUTHOR]

We study marital assortative mating in education and its relation to dowry in India. There are four main results and contributions of this paper. First, instrumental variable estimates using Indian Human Development Survey-II data suggest existence of positive assortative mating in education levels of husband and wife. Second, this association is weaker in dowry-prominent districts suggesting that in districts with strong patriarchal norms, high dowry transfers could substitute for lower bride's education. Third, we study the independent effect of husband's and wife's education and its interaction on dowry. Estimates suggest that dowry rises with the groom's education and falls with the bride's schooling years. However, the joint effect of husband-and-wife education on dowry is negative, implying that though dowry rises with groom's education, the rate of increase is smaller the more educated the bride is. Finally, to explain the empirical results, we propose a theoretical model of assortative mating in the presence of dowry. [ABSTRACT FROM AUTHOR]

Background: Science, technology, engineering, and mathematics (STEM) professionals are regarded as the highly skilled labor force that fosters economic productivity, enterprise innovation, and international competitiveness of a country. This study aims to understand the genetic predisposition to STEM occupations and investigate its associations with regional economic performance. We conducted a genome-wide association study on the occupational choice of STEM jobs based on a sample of 178,976 participants from the UK Biobank database. Results: We identified two genetic loci significantly associated with participants' STEM job choices: rs10048736 on chromosome 2 and rs12903858 on chromosome 15. The SNP heritability of STEM occupations was estimated to be 4.2%. We also found phenotypic and genetic evidence of assortative mating in STEM occupations. At the local authority level, we found that the average polygenic score of STEM is significantly and robustly associated with several metrics of regional economic performance. Conclusions: The current study expands our knowledge of the genetic basis of occupational choice and potential regional disparities in socioeconomic developments. [ABSTRACT FROM AUTHOR]

Research Highlight: Woodman, J. P., Cole, E. F., Firth, J. A., Perrins, C. M., & Sheldon, B. C. (2022). Disentangling the causes of age‐assortative mating in bird populations with contrasting life‐history strategies. Journal of Animal Ecology, https://doi.org/10.1111/1365‐2656.13851. In their study of age‐assortative mating, Woodman and colleagues thoroughly and concisely detail its behavioural determinants using datasets, astonishing in themselves, amassed from their decades‐long studies of mute swans (Cygnus olor) and great tits (Parus major), species that are respectively longer‐ and shorter‐lived and occupying different segments of the slow/fast life‐history continuum. Here, they show that positive age‐assortative mating occurs through active, age‐based mate selection in mute swans which play the long game, whereas in the shorter‐lived great tit this is principally a passive byproduct of demographic processes. That great tits have relatively lower interannual survivorship means that newly recruited, young birds occupy a larger proportion of the breeding population in any given year than occurs in mute swans. The adaptive significance of age‐assortative mating is yet to be determined, but the current study provides an exciting possibility for the role of selection on assortative mating generally in either promoting or constraining active mate selection and sexual dimorphism within and across the tree of life. [ABSTRACT FROM AUTHOR]

Age shapes fundamental processes related to behaviour, survival and reproduction, where age influences reproductive success, non‐random mating with respect to age can magnify or mitigate such effects. Consequently, the correlation in partners' age across a population may influence its productivity. Despite widespread evidence for age‐assortative mating, little is known about what drives this assortment and its variation. Specifically, the relative importance of active (same‐age mate preference) and passive processes (assortment as a consequence of other spatial or temporal effects) in driving age assortment is not well understood.In this paper, we compare breeding data from a great tit and mute swan population (51‐ and 31‐year datasets, respectively) to tease apart the contributions of pair retention, cohort age structure and active age‐related mate selection to age assortment in species with contrasting life histories.Both species show age‐assortative mating and variable assortment between years. However, we demonstrate that the drivers of age assortment differ between the species, as expected from their life histories and resultant demographic differences. In great tits, pair fidelity has a weak effect on age‐assortative mating through pair retention; variation in age assortment is primarily driven by fluctuations in age structure from variable juvenile recruitment. Age‐assortative mating is, therefore, largely passive, with no evidence consistent with active age‐related mate selection. In mute swans, age assortment is partly explained by pair retention, but not population age structure, and evidence exists for active age‐assortative pairing.This difference is likely to result from shorter life‐spans in great tits compared with mute swans, leading to fundamental differences in their population age structure, whereby a larger proportion of great tit populations consist of a single age cohort. In mute swans, age‐assortative pairing through mate selection may also be driven by greater age‐dependent variation in fitness.The study highlights the importance of considering how different life histories and demographic differences arising from these affect population processes that appear congruent across species. We suggest that future research should focus on uncovering the proximate mechanisms that lead to variation in active age‐assortative mate selection (as seen in mute swans); and the consequences of variation in age structure on the ecological and social functioning of wild populations. [ABSTRACT FROM AUTHOR]

Mate choice is a key driver of evolutionary phenomena such as sexual dimorphism. Social mate choice is studied less often than reproductive mate choice, but for species that exhibit biparental care, choice of a social mate may have important implications for offspring survival and success. Many species make pairing decisions based on size that can lead to population-scale pairing patterns such as assortative and disassortative mating by size. Other size-based pairing patterns, such as females pairing with males larger than themselves, have been commonly studied in humans, but less often studied in nonhuman animal systems. Here we show that sexually size-dimorphic mountain chickadees, Poecile gambeli , appear to exhibit multiple self-referential pairing patterns when choosing a social mate. Females paired with males that were larger than themselves more often than expected by chance, and they paired with males that were slightly larger than themselves more often than they paired with males that were much larger than themselves. Preference for slightly larger males versus much larger males did not appear to be driven by reproductive benefits as there were no statistically significant differences in reproductive performance between pairs in which males were slightly larger and pairs in which males were much larger than females. Our results indicate that self-referential pairing beyond positive and negative assortment may be common in nonhuman animal systems. • The factors influencing social mate choice remain unclear. • Some species, including humans, make self-referential pairing decisions. • Mountain chickadees are sexually size dimorphic and socially monogamous. • Females paired with males that were larger but not too much larger than themselves. • Reproductive performance was not related to whether a pair followed this pattern. [ABSTRACT FROM AUTHOR]

This paper unravels the effect of assortative mating on wealth inequality. In light of the reviewed literature, it is concluded that there is a significant effect of assortative mating on wealth inequality, it is mainly driven by similarity in background and similar views on lifestyle, including saving habits. These findings are in line with the matching hypothesis. However, the competition hypothesis of having an inherent interest in a partner with a high socio-economic status cannot be ruled out. Another relevant finding highlights how redistributive policies might enable individuals to cross social boundaries when partnering up and foster social cohesion. [ABSTRACT FROM AUTHOR]

We quantify intergenerational and assortative processes by comparing different degrees of kinship within the same generation. This "horizontal" approach yields more, and more distant kinship moments than traditional methods, which allows us to account for the transmission of latent advantages in a detailed intergenerational model. Using Swedish registers, we find strong persistence in the latent determinants of status, and a striking degree of sorting—to explain the similarity of distant kins, assortative matching must be much stronger than previously thought. Latent genetic influences explain little of the variance in educational attainment, and sorting occurs primarily in non-genetic factors. [ABSTRACT FROM AUTHOR]

Genetic correlation between mates at specific loci can greatly alter the evolutionary trajectory of a species. Genetic assortative mating has been documented in humans, but its existence beyond population stratification (shared ancestry) has been a matter of controversy. Here, we develop a method to measure assortative mating across the genome at 1,044,854 single-nucleotide polymorphisms (SNPs), controlling for population stratification and cohort-specific cryptic relatedness. Using data on 1683 human couples from two data sources, we find evidence for both assortative and disassortative mating at specific, discernible loci throughout the entire genome. Then, using the composite of multiple signals (CMS) score, we also show that the group of SNPs exhibiting the most assortativity has been under stronger recent positive selection. Simulations using realistic inputs confirm that assortative mating might indeed affect changes in allele frequency over time. These results suggest that genetic assortative mating may be speeding up evolution in humans.

Gene flow between populations can allow the spread of beneficial alleles and genetic diversity between populations, with importance to conservation, invasion biology, and agriculture. Levels of gene flow between populations vary not only with distance, but also with divergence in reproductive phenology. Since phenology is often locally adapted, arriving migrants may be reproductively out of synch with residents, which can depress realized gene flow. In flowering plants, the potential impact of phenological divergence on hybridization between populations can be predicted from overlap in flowering schedules-the daily count of flowers capable of pollen exchange-between a resident and migrant population. The accuracy of this prospective hybridization estimate, based on parental phenotypes, rests upon the assumptions of unbiased pollen transfer between resident and migrant active flowers. We tested the impact of phenological divergence on resident-migrant mating frequencies in experiments that mimicked a single large gene flow event. We first prospectively estimated mating frequencies two lines of Brassica rapaselected or early and late flowering. We then estimated realized mating frequencies retrospectively through progeny testing. The two estimates strongly agreed in a greenhouse experiment, where procedures ensured saturating, unbiased pollination. Under natural pollination in the field, the rate of resident-migrant mating, was lower than estimated by phenological divergence alone, although prospective and retrospective estimates were correlated. In both experiments, differences between residents and migrants in flowering schedule shape led to asymmetric hybridization. Results suggest that a prospective estimate of hybridization based on mating schedules can be a useful, although imperfect, tool for evaluating potential gene flow. They also illustrate the impact of mating phenology on the magnitude and symmetry of reproductive isolation.

"The Steerage" is a photograph by Alfred Stieglitz that captures a sense of division between men and women and within different classes of passengers. The author reflects on the growing extreme divisions in many countries today and the psychological obstacles to achieving more equality, particularly in relation to the psychology of inequalities of wealth. The photograph also inspires hope as it depicts people who have worked in America and are returning to their countries of origin. The author shares personal connections to the image and discusses their interest in photographs of crowds and large groups of people. [Extracted from the article]

Introduction: Assortative mating refers describes a phenomenon in which individuals with similar phenotypic traits are more likely to mate and reproduce with each other; i.e. assortative mating occurs when individuals choose partners based on their similarity or dissimilarity in certain traits.to patterns of non-random mating of spouses leading to phenotypic resemblance. There are various theories about the its underlying mechanisms, which have different genetic consequences.Methods: We analyzed examined two possible mechanisms underlying assortative mating – phenotypic assortment and social homogamy – for educational attainment in two countries utilizing data of mono- and dizygotic twins and their spouses (1,451 Finnish and 1,616 Dutch twin-spouse pairs).Results: The spousal correlations were 0.51 in Finland and 0.45 in the Netherlands, to which phenotypic assortment contributed 0.35 and 0.30, and social homogamy 0.16 and 0.15, respectively.Conclusion: Both social homogamy and phenotypic assortment are important processes in spouse selection in Finland and the Netherlands. In both countries, phenotypic assortment contributes to a greater degree to the similarity of spouses than social homogamy.

Migratory diversity can promote population differentiation if sympatric phenotypes become temporally, spatially, or behaviorally segregated during breeding. In this study, the potential for spatiotemporal segregation was tested among three migratory phenotypes of lake sturgeon (Acipenser fulvescens) that spawn in the St. Clair River of North America's Laurentian Great Lakes but differ in how often they migrate into the river and in which direction they move after spawning. Acoustic telemetry over 9 years monitored use of two major spawning sites by lake sturgeon that moved north to overwinter in Lake Huron or south to overwinter in Lake St. Clair. Lake St. Clair migrants were further distinguished by whether they migrated into the St. Clair River each year (annual migrants) or intermittently (intermittent migrants). Social network analyses indicated lake sturgeon generally co-occurred with individuals of the same migratory phenotype more often than with different migratory phenotypes. A direct test for differences in space use revealed one site was almost exclusively visited by Lake St. Clair migrants whereas the other site was visited by Lake Huron migrants, intermittent Lake St. Clair migrants, and, to a lesser extent, annual Lake St. Clair migrants. Analysis of arrival and departure dates indicated opportunity for co-occurrence at the site visited by all phenotypes but showed Lake Huron migrants arrived approximately 2 weeks before Lake St. Clair migrants. Taken together, our results indicated partial spatiotemporal segregation of migratory phenotypes that may generate assortative mating and promote population differentiation. [ABSTRACT FROM AUTHOR]

The present study links the person–environment fit theory of vocational interests (VI) with the research on the selection of romantic partners. Empirically, we explore the assortment for VI in 215 heterosexual romantic partners. Using both the variable‐centered (VCA) and couple‐centered (CCA) approaches, we test the hypotheses on positive versus negative assortment, initial assortment versus convergence, and active assortment versus social homogamy. A modest to moderate positive assortment was found for Realistic, Investigative, Artistic, and Social interests but not Conventional interests, whereas evidence of couple similarity in Enterprising interests was less consistent. A moderate level of positive assortment was identified in couples when full interest profiles were evaluated. The results indicate an initial and active assortment rather than convergence or social homogamy effects. The analysis also shows that the assortment for interests represents an independent preference that cannot be easily seen as a by‐product of the assortment in the five‐factor personality traits. These findings highlight the importance of VI in the active selection of romantic partners. We discuss implications for future research and practice. [ABSTRACT FROM AUTHOR]

Selection along environmental gradients can drive reproductive isolation and speciation. Among fishes, salinity is a major factor limiting species distributions, and despite its importance in generating species diversity, speciation events between marine and freshwater are rare. Here, we tested for mechanisms of reproductive isolation between locally adapted freshwater and brackish water‐native populations of killifish, Fundulus heteroclitus, from either side of a hybrid zone along a salinity gradient. There was evidence for pre‐zygotic endogenous reproductive isolation with reduced fertilization success between crosses of freshwater‐native males and brackish water‐native females. Exogenous pre‐zygotic isolation was also present where females had highest fertilization in their native salinity. We used a replicated mass spawning design to test for mate choice in both brackish and fresh water. After genotyping 187 parents and 2523 offspring at 2347 SNPs across the genome, 85% of offspring were successfully assign to their parents. However, no reinforcing mate choice was observed. These results therefore demonstrate emerging, yet limited, reproductive isolation and incipient speciation across a marine to freshwater salinity gradient and suggest that both endogenous and exogenous mechanisms, but not assortative mating, contribute to divergence. [ABSTRACT FROM AUTHOR]

Using 2010 Japanese census data, we critically interrogate the idea of integration through marriage in Japan. Intermarriage has been seen as a result of integration but the patterns of intermarriage and integration might depend on existing intersecting power structures in the receiving society. We explore assortative mating patterns in bi-national marriages in order to understand how citizenship status, race, gender, and educational level intersect and affect the patterns of intermarriage in Japan. We argue how 'integration' through bi-national marriage only perpetuates the structural hierarchy that premiers and maintain the status of the (male) native Japanese majority over Asian immigrants. [ABSTRACT FROM AUTHOR]

Individually consistent behavioural phenotypes persist in a diversity of populations, despite the expectation that selection would reduce their prevalence. The life-history trade-off between current and future reproduction, combined with individual variation in age or condition and therefore in residual reproductive value, may explain this apparent paradox. Specifically, individuals that are old or of low condition and therefore of low residual reproductive value should take risks and thus elevate current reproduction at the expense of future reproduction. The opposite should be true for individuals that are young or of high condition and therefore of high residual reproductive value, which should be risk averse. Over the course of a long-term study on Lincoln's sparrows, Melospiza lincolnii , we discovered a behavioural phenotype based on trappability that predicts both condition (but not age) and current reproductive success but, surprisingly, in a way that was not expected based on our assumption of how this phenotype is associated with risk taking. We found that, relative to individuals that did not enter traps (the nontrap phenotype, assumed as risk averse), those of the trap phenotype (assumed as risk taking) showed elevated indices of energetic condition and, for females, reduced reproductive success. Assortative mating may be a proximate mechanism for the populationwide maintenance of multiple behavioural phenotypes, and we found that assortative pairings based on trappability phenotype occurred more frequently than random pairing would predict. However, assortative pairing, when compared to disassortative pairing, did not affect reproductive success. Nevertheless, the contrasting relationships between current reproductive success and condition that we found for each phenotype are consistent with life-history theory. However, our results are not consistent with the assumption that the trap phenotype is a manifestation of risk-taking behaviour and may, in fact, arise from just the opposite: a risk-averse, shy or neophobic behaviour for the trap phenotype. • Two phenotypes in a bird species coexist and differ in their life-history strategy. • The trap phenotype (assumed as risk taking) had higher energetic condition. • The nontrap phenotype (assumed as risk averse) had higher reproductive success. • Members of a breeding pair were correlated in phenotype. [ABSTRACT FROM AUTHOR]

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We study assortative mating of Norwegian parents over five decades and its consequences for offspring outcomes. Parents are characterised by the earnings decile of their parents (the offspring's grandparents) as an indicator of social class. While assortative mating has remained stable across decades, parenthood has become more skewed toward the higher classes. Examining the influence on offspring education and employment, we find that the marginal effect of one parent's class is smaller the higher is the class of the other. Overall, mating trends have contributed to slight improvements in average education and employment and reduced inequality in the offspring generation. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study was to investigate assortative mating processes inside Internet-dating-service settings. Unattached consumers traditionally sought to satisfy their need for love through conventional search processes, including old-fashioned match-making. That was then, this is now; dozens of internet-mediated dating websites promising romantic-love-matches currently operate internationally. These dating services cultivate dating-exchanges by offering new-fashioned match-making processes. Despite these trends, theoretical and practical questions related to how and why dating services marketers might induce superior romantic exchanges between customers by managing assortative mating processes remain unanswered until now. Design/methodology/approach: A survey-based approach was used to test hypotheses. Pretests were conducted to develop reliable measures of assortative mating propensity. Seven subconstructs of assortative mating were identified by analyzing data from a representative sample. The measurement model was validated before hypotheses testing. The focal assortative mating construct was measured formatively; assortative mating subdimensions functioned as indicators. The model was tested by structural equation modeling. Findings: Assortative mating processes facilitated superior preference-selection outcomes for individuals seeking consumer-to-consumer romantic relationships inside internet-mediated service settings. Insights were generated about how and why assortative mating processes exercised positive effects on consumers' attitudes toward online dating and about how dating services marketers might leverage assortative mating tendencies to benefit consumers. Originality/value: A novel concept was introduced to the services marketing literature, as were several theoretical implications. The study simultaneously measured consumers' propensities to engage in assortative mating and captured the effects of various physical/behavioral consumer characteristics. This study develops new and practical insights about how dating service marketers could manage the effects of assortative mating processes. [ABSTRACT FROM AUTHOR]

Upon the secondary contact of populations, speciation with gene flow is greatly facilitated when the same pleiotropic loci are both subject to divergent ecological selection and induce non-random mating, leading to loci with this fortuitous combination of functions being referred to as 'magic trait' loci. We use a population genetics model to examine whether 'pseudomagic trait' complexes, composed of physically linked loci fulfilling these two functions, are as efficient in promoting premating isolation as magic traits. We specifically measure the evolution of choosiness, which controls the strength of assortative mating. We show that, surprisingly, pseudomagic trait complexes, and to a lesser extent also physically unlinked loci, can lead to the evolution of considerably stronger assortative mating preferences than do magic traits, provided polymorphism at the involved loci is maintained. This is because assortative mating preferences are generally favoured when there is a risk of producing maladapted recombinants, as occurs with non-magic trait complexes but not with magic traits (since pleiotropy precludes recombination). Contrary to current belief, magic traits may not be the most effective genetic architecture for promoting strong premating isolation. Therefore, distinguishing between magic traits and pseudomagic trait complexes is important when inferring their role in premating isolation. This calls for further fine-scale genomic research on speciation genes. [ABSTRACT FROM AUTHOR]

Mendelian randomization (MR) has become a common tool used in epidemiological studies. However, when confounding variables are correlated with the instrumental variable (in this case, a genetic/variant/marker), the estimation can remain biased even with MR. We propose conditioning on parental mating types (a function of parental genotypes) in MR to eliminate the need for one set of assumptions, thereby plausibly reducing such bias. We illustrate a situation in which the instrumental variable and confounding variables are correlated using two unlinked diallelic genetic loci: one, an instrumental variable and the other, a confounding variable. Assortative mating or population admixture can create an association between the two unlinked loci, which can violate one of the necessary assumptions for MR. We simulated datasets involving assortative mating and population admixture and analyzed them using three different methods: 1) conventional MR, 2) MR conditioning on parental genotypes, and 3) MR conditioning on parental mating types. We demonstrated that conventional MR leads to type I error rate inflation and biased estimates for cases with assortative mating or population admixtures. In the presence of non-additive effects, MR with an adjustment for parental genotypes only partially reduced the type I error rate inflation and bias. In contrast, conditioning on parental mating types in MR eliminated the type I error inflation and bias under these circumstances. Conditioning on parental mating types is a useful strategy to reduce the burden of assumptions and the potential bias in MR when the correlation between the instrument variable and confounders is due to assortative mating or population stratification but not linkage. [ABSTRACT FROM AUTHOR]

Reproductive isolation can occur due to divergence in sexual selection for particular traits. For example, differences in mate preference associated with body size can play an important role in divergence between groups. The importance of mate preference for population divergence may be influenced by other aspects of a mating system, such as the requirement for parental care. In Nova Scotia, Canada, two ecotypes of marine Threespine Stickleback occur sympatrically: a "common" ecotype wherein males provide parental care, and a "white" ecotype that does not exhibit paternal care. The goal of our study was to examine differences in male mate preference between white and common stickleback males to test the prediction that males who invest more in parental care may be more selective about their mates. Because of the link between size and fecundity in this species, we predict that males that invest in parental care should prefer large females, while males that do not provide care will not exhibit preference for larger female size. We found that common male stickleback preferred larger‐bodied females of both ecotypes, while white males showed a preference for larger‐bodied common females. Secondarily, we assessed whether females differed in their willingness to mate with males of different sizes and ecotypes. Common female stickleback had a higher response rate toward smaller white males, which may be associated with their relatively high courtship rates. Counter to previous studies on these ecotypes that suggest that mating is completely assortative, interecotype matings occurred in half of the observed spawning events. This observation, coupled with the results that males may prefer females based mainly on size and females respond to males who court more rigorously regardless of their ecotype, may lend insight into recent genetic evidence for hybridization in the wild. [ABSTRACT FROM AUTHOR]

The harmful effects of close inbreeding have been recognized for centuries and, with the rise of Mendelian genetics, was realized to be an effect of homozygosis. This historical background led to great interest in ways to quantify inbreeding, its depression effects on the phenotype and flow‐on effects on mate choice and other aspects of behavioral ecology. The mechanisms and cues used to avoid inbreeding are varied and include major histocompatibility complex (MHC) molecules and the peptides they transport as predictors of the degree of genetic relatedness. Here, we revisit and complement data from a Swedish population of sand lizards (Lacerta agilis) showing signs of inbreeding depression to assess the effects of genetic relatedness on pair formation in the wild. Parental pairs were less similar at the MHC than expected under random mating but mated at random with respect to microsatellite relatedness. MHC clustered in groups of RFLP bands but no partner preference was observed with respect to partner MHC cluster genotype. Male MHC band patterns were unrelated to their fertilization success in clutches selected for analysis on the basis of showing mixed paternity. Thus, our data suggest that MHC plays a role in pre‐copulatory, but not post‐copulatory partner association, suggesting that MHC is not the driver of fertilization bias and gamete recognition in sand lizards. [ABSTRACT FROM AUTHOR]

Supergenes are clusters of linked loci that control complex phenotypes, such as alternative forms of social organization in ants. Explaining the long‐term maintenance of supergenes is challenging, particularly when the derived haplotype lacks homozygous lethality and causes gene drive. In the Alpine silver ant, Formica selysi, a large and ancient social supergene with two haplotypes, M and P, controls colony social organization. Single‐queen colonies only contain MM females, while multiqueen colonies contain MP and PP females. The derived P haplotype, found only in multiqueen colonies, selfishly enhances its transmission through maternal effect killing, which could have led to its fixation. A population genetic model showed that a stable social polymorphism can only be maintained under a narrow set of conditions, which includes partial assortative mating by social form (which is known to occur in the wild), and low fitness of PP queens. With a combination of field and laboratory experiments, we show that the P haplotype has deleterious effects on female fitness. The survival rate of PP queens and workers was around half that of other genotypes. Moreover, P‐carrying queens had lower fertility and fecundity compared to other queens. We discuss how cryptic lethal effects of the P haplotype help stabilize this ancient polymorphism. [ABSTRACT FROM AUTHOR]

It is now acknowledged that mating system is a dynamic characteristic within species or populations. Indeed, behavioural characteristics shaping the mating system can vary at the inter‐individual level, providing raw material for sexual and natural selections, and at the intra‐individual level, because of phenotypic plasticity and ontogeny of individual behaviours. Social environment is an additional source of variation in sexual behaviours. By focusing on males of the parasitoid wasp Venturia canescens, we assessed how sexual behaviours (courtship and mating) vary between and within individuals, considering males' size as inter‐individual source of variation, and age and mating experience as intra‐individual sources of variation. Consequences of the variations in sexual behaviours at the individual level are appraised by quantifying the costs in longevity and offspring production incurred by (repeatedly) mated males. At the population level, we tested the "agility hypothesis" predicting that smaller males win the male–male competition to access females, resulting in a non‐random assortative mating by size and a negative sexual selection on body size. We showed that V. canescens males are polygynous and that mating incurred longevity cost. Old males had a higher probability to court females, but no mating advantage. Smaller males tended to have a higher mating probability, but size was not under sexual selection and there was a random mating pattern according to individual size. Male–male competition intensity did not influence pairing pattern but tended to influence mating dynamic. Overall, our results suggest that sexual behaviours tended to vary at the inter‐ and intra‐individual levels and the effect of social environment remains to be more precisely described. These variations may impact individuals' reproductive success with potential ecological and evolutionary consequences that are discussed. [ABSTRACT FROM AUTHOR]

Recent research into intergenerational social mobility has examined the association between the socioeconomic position of grandparents (G1) and their grandchildren (G3), but it remains unclear why G1-G3 associations arise. Prevailing explanations focus on whether grandparents have a true direct influence on their grandchildren or an indirect one via omitted parental characteristics. We argue that there may be other important indirect pathways of multigenerational persistence: grandparents can transmit resources via uncles and aunts, and they can encourage assortative mating in the middle generation, which also increases the resources available to their grandchildren. We examine these indirect pathways by studying the status attainment of 176,678 Dutch men for the period 1857 to 1922 using marriage certificates. Results show that G3ʹs status was substantially associated with uncles' status and that assortative mating based on social origin was strong. Accounting for these associations reduces much of the G1-G3 association. We therefore conclude that multigenerational persistence arose hardly because grandfathers had a direct influence but rather because grandfathers were important in more indirect ways. [ABSTRACT FROM AUTHOR]

This study examines the impact of higher education on women's bargaining power in the household in South Korea. Utilising the nationwide college expansion programs in South Korea in 1979 and 1981 as a natural experiment, this study uses 6181 married women born between 1943 and 1976 and adopts the birth cohort as an instrumental variable to identify women that benefitted from the programs. The results show that more years of schooling increased women's property ownership and decision-making power at home, which is further explained by three channels. The first channel, related to women's economic resources, indicates that education increased women's likelihood of being employed, having a white-collar job, absolute income, and age at marriage. However, it did not increase women's relative income compared to their husbands'. Second, consistent with the assortative mating theory, higher education encouraged women to marry a partner who has a prestigious job and is closer to their education level and age. Third, the channel of gender role attitudes revealed that more years of schooling led women to realize the need for financial independence from their spouses. These findings show how access to higher education for women improved gender equality in South Korean society. [ABSTRACT FROM AUTHOR]

We develop a method which assumes that marital preferences are characterized either by the scalar-valued measure proposed by Liu and Lu, or by the matrix-valued generalized Liu–Lu measure. The new method transforms an observed contingency table into a counterfactual table while preserving its (generalized) Liu–Lu value. After exploring some analytical properties of the new method, we illustrate its application by decomposing changes in the prevalence of homogamy in the US between 1980 and 2010. We perform this decomposition with two alternative transformation methods as well where both methods capture preferences differently from Liu and Lu. Finally, we use survey evidence to support our claim that out of the three considered methods, the new transformation method is the most suitable for identifying the role of marital preferences at shaping marriage patterns. These data are also in favor of measuring assortativity in preferences à la Liu and Lu. [ABSTRACT FROM AUTHOR]

Most of the 500+ cichlid species of Lake Victoria evolved very rapidly in the wake of an adaptive radiation within the last 15,000 years. All 500 species have evolved from just one out of five old cichlid lineages that colonized the lake. Endemic to the Lake Victoria region, Astatoreochromis alluaudi is a member of an old haplochromine lineage that never speciated in the region. Even though the species occurs in a wide range of habitats, there were no indications of evolutionary diversification. Here, we tested predictions of several hypothetical mechanisms that might constrain speciation, including high dispersal rates, a generalist life style and the lack of behavioral assortative mating. Genomic analyses of individuals from 13 populations revealed several genomically distinct groups, associated with major habitat classes, indicating the existence of two distinct ecotypes. We found significant phenotypic differences between these ecotypes in the wild, which were retained under common-garden conditions, potentially indicating heritable phenotypic adaptations. Female mate choice experiments revealed the absence of behavioral assortative mating despite genetic and phenotypic differentiation between ecotypes. We suggest that the lack of coupling between behavioral mating preferences and phenotypic and genetic divergence constrains speciation in this cichlid. [ABSTRACT FROM AUTHOR]

Bowen theory describes how a couple's functioning is influenced by the emotional processes between the couple and within the family. Through this lens this study examined similarity in the levels of husband-wife symptomology. In the study sample, higher functioning families more frequently had spouses with similar, lower levels of symptomology which were steady over time. In lower functioning families there was less frequent spouse similarity in functioning, higher levels of spouse symptomology, more year-to-year fluctuation in husband-wife symptomology, and more divergent spouse functioning. The researcher contends that similar spouse symptomology was probably influenced by spouses marrying at the same basic level of differentiation and by the effects over time of the couple's level of differentiation and the family's emotional processes. Higher levels of differentiation seemed to have moderated the family stress response and contributed to stable, similar husband-wife functioning. At lower levels of differentiation the emotional processes that appeared more frequently to contribute to spouse similarity and convergence were spouses mutually losing self, mutually binding anxiety in physical, psychiatric, and/or social symptoms, mutually projecting immaturity and tension onto another, and/or distancing. [ABSTRACT FROM AUTHOR]