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The emergence and persistence of polymorphism within populations generally requires specific regimes of natural or sexual selection. Here, we develop a unified theoretical framework to explore how polymorphism at targeted loci can be generated and maintained by either disassortative mating choice or balancing selection due to, for example, heterozygote advantage. To this aim, we model the dynamics of alleles at a single locus A in a population of haploid individuals, where reproductive success depends on the combination of alleles carried by the parents at locus A. Our theoretical study of the model confirms that the conditions for the persistence of a given level of allelic polymorphism depend on the relative reproductive advantages among pairs of individuals. Interestingly, equilibria with unbalanced allelic frequencies were shown to emerge from successive introduction of mutants. We then investigate the role of the function linking allelic divergence to reproductive advantage on the evolutionary fate of alleles within the population. Our results highlight the significance of the shape of this function for both the number of alleles maintained and their level of genetic divergence. Large number of alleles are maintained with substantial replacement of alleles, when disassortative advantage slowly increases with allelic differentiation. In contrast, few highly differentiated alleles are predicted to be maintained when genetic differentiation has a strong effect on disassortative advantage. These opposite effects predicted by our model explain how disassortative mate choice may lead to various levels of allelic differentiation and polymorphism, and shed light on the effect of mate preferences on the persistence of balanced and unbalanced polymorphism in natural population. [ABSTRACT FROM AUTHOR]

In China, a critical challenge for rural-to-urban migrants planning to settle down is to convert their rural hukou (household registration) to an urban one through a limited set of de jure channels. This study argues that marriage is a key channel that some migrants take, notably for female migrants. Using data from the 2010 Chinese General Social Survey, we analyzed how educational and age disparities between female rural-to-urban migrants and their husbands relate to urban hukou conversion. We found that the rural women who used marriage as the means to hukou conversion were more likely to marry someone less educated and much older. The findings suggest that rural women can realize their geographical and social mobility by a strategic response to the residence policy, which may in turn impact the dynamics of gender inequality in the household. [ABSTRACT FROM AUTHOR]

• Oogoniogamy was observed in Chlamydomonas proboscigera for the first time. • Copulation occurred at different sites on the cell's surface. • Oogoniogamy was observed under low temperature conditions. • Sexual reproduction by oogoniogamy may be successful overwintering stages. A unique opportunity to study the sexual reproduction of Chlamydomonas proboscigera was presented when this species reached high densities in the Vaal River, South Africa during 2019. A peculiar and unique way of sexual reproduction in C. proboscigera was revealed for the first time and differs from earlier knowledge on the sexual reproduction of this species. Evidence of copulating gametes obtained during the study proved that C. proboscigera can also reproduce sexually by oogoniogamy and not only through isogamy, as previously believed. Gametes of different sizes copulated with each other and in addition to previously described copulation sites, results of this study indicated that gametes may attach to each other at different sites on the cell surface, including at their posterior ends, the posterior end of one gamete can attach to the side of the other gamete (laterally) or the posterior end of one gamete may attach sub-apically to the other gamete. Data on environmental variables at the time of sexual reproduction showed that oogoniogamy occurred under clear water conditions with low temperatures, sufficient nutrient concentrations, and slightly alkaline pH levels. Low temperatures may have played a role in inducing sexual reproduction to form resistant overwintering stages in the form of zygospores. [ABSTRACT FROM AUTHOR]

The tempo of sex chromosome evolution—how quickly, in what order, why and how their particular characteristics emerge during evolution—remains poorly understood. To understand this further, we studied three closely related species of African clawed frog (genus Xenopus), that each has independently evolved sex chromosomes. We identified population polymorphism in the extent of sex chromosome differentiation in wild-caught Xenopus borealis that corresponds to a large, previously identified region of recombination suppression. This large sex-linked region of X. borealis has an extreme concentration of genes that encode transcripts with sex-biased expression, and we recovered similar findings in the smaller sex-linked regions of Xenopus laevis and Xenopus tropicalis. In two of these species, strong skews in expression (mostly female-biased in X. borealis, mostly male-biased in X. tropicalis) are consistent with expectations associated with recombination suppression, and in X. borealis, we hypothesize that a degenerate ancestral Y-chromosome transitioned into its contemporary Z-chromosome. These findings indicate that Xenopus species are tolerant of differences between the sexes in dosage of the products of multiple genes, and offer insights into how evolutionary transformations of ancestral sex chromosomes carry forward to affect the function of new sex chromosomes. This article is part of the theme issue 'Challenging the paradigm in sex chromosome evolution: empirical and theoretical insights with a focus on vertebrates (Part I)'. [ABSTRACT FROM AUTHOR]

The tempo of sex chromosome evolution-how quickly, in what order, why and how their particular characteristics emerge during evolution-remains poorly understood. To understand this further, we studied three closely related species of African clawed frog (genus Xenopus), that each has independently evolved sex chromosomes. We identified population polymorphism in the extent of sex chromosome differentiation in wildcaught Xenopus borealis that corresponds to a large, previously identified region of recombination suppression. This large sex-linked region of X. borealis has an extreme concentration of genes that encode transcripts with sex-biased expression, and we recovered similar findings in the smaller sex-linked regions of Xenopus laevis and Xenopus tropicalis. In two of these species, strong skews in expression (mostly female-biased in X. borealis, mostly male-biased in X. tropicalis) are consistent with expectations associated with recombination suppression, and in X. borealis, we hypothesize that a degenerate ancestral Y-chromosome transitioned into its contemporary Z-chromosome. These findings indicate that Xenopus species are tolerant of differences between the sexes in dosage of the products of multiple genes, and offer insights into how evolutionary transformations of ancestral sex chromosomes carry forward to affect the function of new sex chromosomes. [ABSTRACT FROM AUTHOR]

Seeking to overcome the heterosexual bias in marriage-migration scholarship and move beyond individualistic approaches to queer mobility, this article focuses on the lives of same-sex couples that hold unequal residence statuses. In a twofold context marked by the increasing legal recognition of same-sex families combined with heightened hurdles facing certain categories of immigrants, we examine what those simultaneous trends mean for these couples. Based on 42 interviews conducted in France, the Netherlands and the United States with people from a variety of class backgrounds, we show how higher resource levels moderate the impact of constraining legal frameworks without suppressing them. We distinguish between low-resource homogamous, heterogamous, and high-resource homogamous couples. The first configuration often results in forced immobility and separation. In heterogamous couples, conjugality becomes a major pathway to legal status for the migrant spouse – potentially feeding suspicions of instrumentality. In contrast, privileged migrants in a homogamous couple tend to relate to law in less of a binary way and experience regulations as more easily surmountable. Yet, for them, securing permanent residence represents but one objective among several (including their careers and studies), an investment often disconnected from their matrimonial relationship and at times in competition with it. [ABSTRACT FROM AUTHOR]

In Western societies, religious heterogamy and its effects on religious socialization outcomes have been interpreted through the lens of secularization. How about China, where religion has been resurging in recent decades? Using data from the 2007 Spiritual Life Survey of Chinese Residents, this study shows that despite China's atheist education system and strict religion policies, having at least one religiously affiliated parent is associated with increased religiosity compared to having two nonreligious parents. Whereas religious heterogamy in the West has a secularizing effect on the next generation, religious heterogamy in secular nations, such as China, has a religionizing effect and contributes to religion's rise. [ABSTRACT FROM AUTHOR]

Objectives Prior research points to the importance of couple-level religious similarity for multiple dimensions of partnership quality and stability but few studies have investigated whether this association holds for older couples. Method The current article uses dyadic data from the National Social Life, Health, and Aging Project (NSHAP), a representative sample of 953 individuals age 62–91 plus their marital or cohabiting partners. We use modified actor-partner interdependence models. Results Religious service heterogamy predicted lower relationship happiness and satisfaction. Both associations were partially explained by the fact that religiously dissimilar partners report relatively little free time in joint activity. Further, religiously heterogamous couples had less frequent sex and engaged in less nonsexual touch than their more similar counterparts. Conclusions Taken together, results attest to the ongoing importance of religious similarity—service attendance, in particular—for partnership quality in late life. Future research is needed to more fully examine which mechanisms account for these patterns. [ABSTRACT FROM AUTHOR]

This study examines patterns of homogamy and heterogamy and their implications for couple’s fertility behaviour. Data were obtained from demographic and health surveys conducted in Ghana, Nigeria and Zambia between 2001 and 2014. The study population were couples in a monogamous union where wives were aged 35 years and over: 1785 in Ghana, 3185 in Nigeria and 3175 in Zambia. Results of the descriptive analysis show that educational, religious and ethnic homogamy and occupational heterogamy were predominant among the couples and mean children ever born varied according to couples’ characteristics. The significant predictors of fertility as revealed in the multivariate analysis included educational homogamy and heterogamy, occupational homogamy, age difference and religious and ethnic homogamy. To expedite fertility transition in the three countries and other sub-Saharan African countries, programmes and policies aimed at reducing fertility in the region should incorporate strategies that focus on the characteristics of couples in union. [ABSTRACT FROM PUBLISHER]

This paper presents the general determinations of interculturalism, intercultural communication, marriage and mixed marriage. Attention is directed to the general conditions that are conducive to mixed marriages, as well as the conditions that inhibit them. In the focus of consideration are the mixed marriages in Vojvodina and features of heterogamy that occurs in this region, while the analysis derived from the available data of the 2011 Census in Serbia. Special attention was paid to the frequency of heterogeneous marriages in relation to the total number of marriages in Vojvodina for the period from 2003 to 2013. The paper also discusses some indicators of the manifestation of interculturalism in mixed marriages, and points to the need and possible directions for their more detailed study. [ABSTRACT FROM AUTHOR]

We propose a new model of permanent monogamous pair formation in zoological populations with multiple types of females and males. According to this model, animals randomly encounter members of the opposite sex at their so-called firing times to form temporary pairs which then become permanent if mating happens. Given the distributions of the firing times and the mating preferences upon encounter, we analyze the contingency table of permanent pair types in three cases: (i) definite mating upon encounter; (ii) Poisson firing times; and (iii) Bernoulli firing times. In the first case, the contingency table has a multiple hypergeometric distribution which implies panmixia. The other two cases generalize the encounter-mating models of Gimelfarb (Am. Nat. 131(6):865-884, 1988) who gives conditions that he conjectures to be sufficient for panmixia. We formulate adaptations of his conditions and prove that they not only characterize panmixia but also allow us to reduce the model to the first case by changing its underlying parameters. Finally, when there are only two types of females and males, we provide a full characterization of panmixia, homogamy and heterogamy. [ABSTRACT FROM AUTHOR]

Past research on religious homogamy has struggled to distinguish whether religiosity or homogamy has a stronger impact on preventing a marital dissolution. To rectify this problem, I use a latent class approach to compare couples with various forms of partner religiosity and similarity. Based on 707 newlywed couples from the Marriage Matters survey (1998–2004), I discovered four latent classes: “holy” couples (both partners are highly religious), “nonattending” couples (both partners identify as religious but don’t regularly attend services), “unbalanced” couples (the wife is religious but the husband is not), and “secular” couples (both partners are not religious). Findings indicate that holy, nonattending, and unbalanced couples experience less odds of divorce compared with secular couples, suggesting that religiosity in a variety of forms is more important than partner similarity in avoiding divorce. [ABSTRACT FROM PUBLISHER]

Interracial couples continue to grow in numbers, though there has been little research aimed to understand the experiences and unique challenges of this population. Among these challenges are stressors associated with the interplay between cultural differences and similarities. In this paper, we present an intervention called the visible invisible grid, that can be used to help interracial and intercultural couples discuss their invisible and visible differences and similarities. To illustrate the intervention, a case example is provided along with contraindications and clinical implications. [ABSTRACT FROM AUTHOR]

Socio-demographic heterogamy is commonly believed to lead to lower relationship stability due to the presence of cultural differences between partners. This explanation lacks empirical support, as psychology studies have not confirmed the link between heterogamy and cultural differences, whereas sociological studies have been characterized by problems related to the choice and measurement of cultural differences. Progressing from previous research, this article examines the specific link between educational heterogamy and cultural differences in the domain of child-rearing. Results partly confirm the alternative hypotheses of child-rearing values and behaviors being subject to gender differences and processes of selection between partners. Nonetheless, they also indicate a positive link between educational heterogamy and differences in child-rearing values and behaviors between partners. [ABSTRACT FROM PUBLISHER]

A common stereotype holds that in Mexico male violence toward women is common among indigenous peoples and reflects cultural norms that sanction a male's domination of his female partner. We employ a recent Mexican survey to examine the relative risk of violence against women as a function of the couple's ethnic homogamy. Among couples in which both partners are either non-indigenous or indigenous the female's risk of partner violence is similar. Among heterogamous couples non-indigenous females in relationships in which the male is indigenous are at elevated risk of violence, while indigenous women in relationships with non-indigenous males are at a lower risk of violence. The stresses associated with heterogamy appear to be more salient in determining a woman's risk of violence than ethnicity per se. The implications for future research and the need to deal with the issue of ethnic homogamy in culturally heterogeneous populations are discussed. [ABSTRACT FROM PUBLISHER]

Marriage between homosexuals has been legally recognised in Spain since 2005. This phenomenon has made visible many couples who lived "underground", regardless of the nationality of the spouses. The purpose of this article is to discover the main patterns of same-sex marriage in which one spouse is Spanish and the other foreign. The Movimiento Natural de Población (National Population Movement) (MNP) is the source of statistics used in this study, as it has the most up-to-date data on this subject. The data show that, depending on the country of origin of the spouses, same-sex marriages in Spain are more heterogamous than heterosexual marriages. Equally, this greater heterogamy is shown in terms of age, occupation and education level. [ABSTRACT FROM AUTHOR]

Marrying someone from an outside group deserves more sociological attention since it may lead to an unstable or even conflicting relationship for the prospective couple. In spite of such a risk, many people still choose to marry someone from an outside group. Traditionally, scholars in the area of social stratification have considered homogamy to be an indicator of social closure. Sociologists have also focused on the status resemblance of marriage partners in that it indicates the extent of social rigidity. However, instead of focusing on status homogamy, this study examines the heterogamy of marriage patterns, which is an alternative way of revealing the degree of social openness. Heterogamy is a more powerful indicator of social openness than homogamy because certain types of heterogamy have to defy the expectations of and/or opposition from the marriage partner's family, community or society! and such instances can be conceptually interpreted as crossing the strongest social boundaries between social groups. Marriages crossing the boundaries of age, education, social origin and ethnicity have been regarded as the four major types of heterogamy. This study uses binary logistic and multinomial logistic models to explore the relative effect of the factors that contribute to cross-boundary marriages. Using data from the Taiwan Social Change Survey, this study demonstrates that certain factors, such as achieved status (education), contextual characteristics (timing of marriage, setting of contacts) and ways of making acquaintances with the prospective spouse have contributed to cross-boundary marriages. Although achieved status and personal traits both have strong effects on the likelihood of heterogamy, social backgrounds and the process of meeting/courting also have a substantial impact on the formation of cross-boundary marriages in Taiwan. [ABSTRACT FROM AUTHOR]

The mechanisms that favor reproductive isolation are a topic of study in the evolutionary process of plants. Subjecting domestic plants to artificial selection could be considered as a biological model in sympatric speciation. The morphology of the flower and the phenological stage of blooming of Hyptis suaveolens: wild, weed and domesticated forms were studied. Significant differences were observed in the floral structure (P<0.05): in the size of the flower tube (highest in the domesticated form), length of style (highest in the wild form), filament's stamens and anthers (highest in the wild form). There was also a significant difference in respect to length of the blooming period (P<0.001): 20.2 and 24 days in the domestic and wild forms, respectively. The weed population showed intermediate values suggesting wild-domestic hybridizing and genetic infiltration. It was inferred (suggested) that artificial selection produces changes that allows autogamy in the domestic variety of H. suaveolens, thus favoring the process towards reproductive isolation. [ABSTRACT FROM AUTHOR]

A textbook hypothesis about divorce is that heterogamous marriages are more likely to end in divorce than homogamous marriages. We analyse vital statistics on the population of the Netherlands, which provide a unique and powerful opportunity to test this hypothesis. All marriages formed between 1974 and 1984 (nearly 1 million marriages) are traced in the divorce records and multivariate logistic regression models are used to analyse the effects on divorce of heterogamy in religion and national origin. Our analyses confirm the hypothesis for marriages that cross the Protestant-Catholic or the Jewish-Gentile boundary. Heterogamy effects are weaker for marriages involving Protestants or unaffiliated persons. Marriages between Dutch and other nationalities have a higher risk of divorce, the more so the greater the cultural differences between the two groups. Overall, the evidence supports the view that, in the Netherlands, new group boundaries are more difficult to cross than old group boundaries. [ABSTRACT FROM AUTHOR]

According to previous cytological evidence, the hemisexual dog-rose species, Rosa sect. Caninae, transmit only seven chromosomes (derived from seven bivalents) through their pollen grains, whereas egg cells contain 21, 28 or 35 chromosomes (derived from seven bivalents and 14, 21 or 28 univalents) depending on ploidy level. Two sets of reciprocal pairwise interspecific crosses involving the pentaploid species pair R. dumalis and R. rubiginosa, and the pentaploid/tetraploid species pair R. sherardii and R. villosa, were analysed for 13 and 12 microsatellite DNA loci, respectively. Single loci were represented by a maximum of three simultaneously occurring alleles in R. villosa, and four alleles in the other three parental plants. In the experimentally derived offspring, the theoretical maximum of five alleles was found for only one locus in the pentaploid progenies. Microsatellite DNA allele composition was identical with that of the maternal parent in 10 offspring plants, which were probably derived through apomixis. Almost all microsatellite DNA alleles were shared with the maternal parent also in the remaining offspring, but 1-4 alleles shared only with the paternal parent, indicating sexual seed formation. Analysis of quantitative peak differences allowed a tentative estimation of allelic configuration in the individual plants, and suggested that bivalent formation preferentially takes place between chromosomes that consistently share the same microsatellite alleles and therefore appear to be highly homologous. Moreover, alleles that were shared between the species in each cross combination comparatively often appear to reside on the bivalent-forming chromosomes, whereas species-specific alleles instead occur comparatively often on the univalent-forming chromosomes and are therefore inherited through the maternal parent only. Recombination then takes place between very similar genomes also in interspecific crosses, resulting in a reproduction system that is essentially a mixture between apomixis and selfing.Heredity (2004) 92, 139-150, advance online publication, 17 December 2003; doi:10.1038/sj.hdy.6800332 [ABSTRACT FROM AUTHOR]

Artificial F1 hybrids within dog-roses (Rosa section Caninae (DC.) Ser.) have been assessed for expression of morphological characters with regards to the actual taxonomy applied. In the mostly pentaploid members of the section the unique heterogamous Canina-meiosis leads to matroclinal inheritance of characters by transmitting 4/5 of the genetic information via seed donor whereas 1/5 is provided by the pollen donor. Evaluation of phenotypic variability revealed that the two taxonomically relevant characters “widening of the orifice” and “persistence of the sepals” are statistically significant controlled by the pollen donor. Reciprocal crossings confirmed the same pattern. One possible explanation is that this phenomenon might be subject to genomic imprinting mechanisms. The morphological analysis gives clear evidence that conventional taxonomical concept is artificial and does not reflect the evolutionary patterns among dog-roses. [ABSTRACT FROM AUTHOR]