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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]

Although most Americans have limited interpersonal relations with different-race others, interracial ties are notably more common among gay, lesbian, and bisexual (GLB) individuals. Departing from the modal explanation of intergroup relations theories, which suggests that individual propensities for between-group interactions are driven by demographic groups’ physical location relative to one another, we show that, beyond propinquity, GLB interraciality is spiked through active identification as GLB. We evaluate full romantic/sexual partnership histories along with friendship network racial compositions for respondents in a large, nationally representative sample. We show that GLBs have a greater likelihood and frequency than heterosexuals of forming multiple types of interracial ties and also that this effect applies only to those who actively identify as GLB and not to those who engage in same-sex relations but do not identify as GLB. This discovery refines theories of intergroup relations, isolating how identification serves as a mediating mechanism that can heighten the propensity for intergroup interaction. We argue that active identification with a group that crosses racial boundaries spurs overriding the rigidity of intergroup borders that otherwise dissuade interpersonal diversity.

Data from the 2010–2012 National Survey of Sexual Attitudes and Lifestyles (NATSAL-3) are used to document trends and patterns in where co-resident couples in Britain first met, focusing specifically on the rapid rise of meeting online, which both echoes and differs from a corresponding US increase; in Britain, meeting online largely appears to have substituted for meetings in settings to which access is relatively unrestricted, for example, pubs and public places. While meeting online appears widespread across British society, variations are identified and linked to ideas from the online dating and place of meeting literatures. Offline partner availability and how well the processes within offline and online settings suit particular types of people are interpreted as underpinning many of these variations. Perhaps surprisingly, meeting online does not appear class-related, and involves levels of socio-demographic homogamy that do not differ systematically from those for compositionally heterogeneous offline settings. [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]

Although most Americans have limited interpersonal relations with different-race others, interracial ties are notably more common among gay, lesbian, and bisexual (GLB) individuals. Departing from the modal explanation of intergroup relations theories, which suggests that individual propensities for between-group interactions are driven by demographic groups' physical location relative to one another, we show that, beyond propinquity, GLB interraciality is spiked through active identification as GLB. We evaluate full romantic/sexual partnership histories along with friendship network racial compositions for respondents in a large, nationally representative sample. We show that GLBs have a greater likelihood and frequency than heterosexuals of forming multiple types of interracial ties and also that this effect applies only to those who actively identify as GLB and not to those who engage in same-sex relations but do not identify as GLB. This discovery refines theories of intergroup relations, isolating how identification serves as a mediating mechanism that can heighten the propensity for intergroup interaction. We argue that active identification with a group that crosses racial boundaries spurs overriding the rigidity of intergroup borders that otherwise dissuade interpersonal diversity. [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]

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]

Heterogamous marriages, in which partners have dissimilar attributes (e.g. by socio-economic status or ethnicity), are often at elevated risk of dissolution. We investigated the influences of heterogamy by religion and area of residence on risk of marital dissolution in Northern Ireland, a country with a history of conflict and residential segregation along Catholic-Protestant lines. We expected Catholic-Protestant marriages to have elevated risks of dissolution, especially in areas with high concentrations of a single religious group where opposition to intermarriage was expected to be high. We estimated risks of marital dissolution from 2001 to 2011 for 19,791 couples drawn from the Northern Ireland Longitudinal Study (a record linkage study), adjusting for a range of compositional and contextual factors using multilevel logistic regression. Dissolution risk decreased with increasing age and higher socio-economic status. Catholic-Protestant marriages were rare (5.9 % of the sample) and were at increased risk of dissolution relative to homogamous marriages. We found no association between local population composition and dissolution risk for Catholic-Protestant couples, indicating that partner and household characteristics may have a greater influence on dissolution risk than the wider community. [ABSTRACT FROM AUTHOR]

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]

Decisions about which contraceptives to use are a key component of a couple's "fertility work," and these decisions can be made in homogamous or heterogamous couple contexts. Relative resource theory and the strain perspective suggest that heterogamy may lead to differences in bargaining power or higher levels of discordance within couples, thereby affecting the distribution of fertility work and decisions about which contraceptives a couple will use. While heterogamy has been linked to less effective contraceptive use amongst teenagers, its role in the contraceptive behavior of married and cohabiting women has been less widely studied. This study examines the association between relationship context in terms of education, age, and race/ethnicity heterogamy and partnered women's use of contraceptives. We used data on partnered women aged 20–45 who were trying to avoid pregnancy from the 2006–2015 National Survey of Family Growth (n = 8097). We used multinomial logistic regressions to determine whether education, age, or race/ethnicity heterogamy was associated with the use of male or female sterilization, long-acting reversible contraceptives (LARCs), other hormonal contraceptives, or other non-hormonal methods. We did not find consistent evidence that relative bargaining power due to higher education, more advanced age, or racial/ethnic privilege resulted in the use of methods requiring lower levels of fertility work. We found some evidence supporting the strain perspective. Younger women (20−34) who differed from their partners along two or more dimensions were less likely to use contraceptive methods requiring ongoing effort and coordination (i.e., LARCs, other hormonal methods, and non-hormonal methods). This association was not observed among women aged 35–45. Despite the more permanent nature of marriage/cohabitation, differences between partners in heterogamous relationships may factor into the contraceptive decision-making process, especially among younger adults at earlier stages of their relationships. • Couple composition shapes contraception work across the reproductive life cycle. • Among younger adults, education, age, and race/ethnicity heterogamy are associated with contraceptive decision-making. • Women (20-34) in couples differing along ≥2 dimensions were less likely to use contraceptives needing ongoing fertility work. • Research is needed to understand whether this association among younger women is due to increased relationship strain. • Contraceptive programs focusing on the couple context – among both adolescents and adult partnered women and men – are needed. [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]

This article examines the effects of parental educational levels on the art/heritage and pop/rock participation of adolescents. We use a subset of adolescents from the survey ‘Cultural Participation in Flanders 2003–2004’ (N = 1030) to test the relative effects of the educational levels of the mother and father. Using diagonal reference models, we find that the parent with the highest educational level – regardless of whether it is the father or mother – has the largest influence on the cultural participation of their children, which can be interpreted as a status maximization effect. However, we also find that a lower educated mother still has an influence on art and heritage participation and a lower educated father still has an influence on pop and rock participation. These results highlight the need to reassess the influence of the mother in the Bourdieusian framework. Furthermore, they have important implications for the conceptualization and operationalization of the social status position of families. [ABSTRACT FROM PUBLISHER]

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., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

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]

This article tackles the issue of marital homogamy in the Czech Republic using paired-data gather in 2005 on a representative sample of people aged 20-40. The aim is to find an answer to the question whether homogamy or heterogamy has any practical meaning for people who live either in marriage or in cohabitation, to explore the differences in opinions with regard to marriage, childcare, gender roles and the reconciliation of family and paid work. We hypothesize that heterogamous couples will be more distant in their attitudes than homogamous couples. The results point out that the homogamy and partners' closeness in answers are not related. Few explanations are offered in the end as a possible answer to why the working hypothesis was rejected. [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]

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]

All members of Rosa section Caninae, dogroses are polyploid and characterized by their unbalanced meiosis, which in most cases leads to a pronounced morphological influence from the maternal parent. In a previous investigation on a pair of reciprocal crosses between two species in this section, Rosa dumalis and R. rubiginosa (2n=35), nine offspring plants (approximately 10%) did not receive any of the 21 RAPD markers present in the respective pollen parent. This was interpreted as a possible occurrence of apomixis. These nine plants have now been subjected to a further study with additional markers. Thirteen new RAPD markers showed the same result as in the previous investigation: none of the nine plants inherited any of the pollen donor markers. The reproducibility of the RAPD markers was checked by mixing DNA samples to obtain a series of artificial hybrids between the two parent plants. Twelve RAPD markers gave the expected result, whereas one marker appeared only 50% of the time. In addition, pollen viability, mean number of seeds per hip, mean seed weight, and mean weight of fruit flesh per hip have been studied on the four progeny groups: R. dumalis× R. rubiginosa plants which received pollen donor markers (PM plants), R. dumalis× R. rubiginosa plants which did not receive any pollen donor markers (NPM plants), R. rubiginosa× R. dumalis PM plants and R. rubiginosa× R. dumalis NPM plants. A canonical discriminant analysis based on these four reproductive characters separated the four progeny groups. There were significant differences between the two PM groups in all investigated characters, and also between the PM and the NPM groups in pollen viability. The result from the RAPD markers together with the differences in pollen viability between the PM and NPM progeny groups is taken as an indication that apomixis occurs within the Caninae section. [ABSTRACT FROM AUTHOR]

The dogroses, Rosa sect. Caninae, are polyploid and characterized by their unique meiosis with an unequal number of chromosomes in the male and female gametes. The pollen cells have 7 chromosomes and the egg cells 21, 28 or 35 depending on the ploidy level of the species. The resulting matroclinal inheritance was studied with both morphological and molecular markers in a pair of reciprocal crosses between R. dumalis and R. rubiginosa (2n=35). A canonical discriminant analysis based on seven morphological characters showed only a minor overlapping between the two progeny groups. In addition, the R. dumalis× R. rubiginosa offspring were more heterogeneous than the offspring from the reciprocal cross in each of the characters analysed. Eleven RAPD markers specific for the R. dumalis parent and 10 RAPD markers specific for the R. rubiginosa parent were scored in the offspring. Each of the offspring exhibited either all, or all-but-one, of the seed parent markers. The average number of pollen donor markers found in the offspring was 3.2 ( R. dumalis× R. rubiginosa) and 2.7 ( R. rubiginosa× R. dumalis). About half of the pollen donor markers were never transmitted to the progeny. This is, to our knowledge, the first time the highly skewed chromosome distribution in Rosa sect. Caninae has been demonstrated with statistically evaluated morphological data and with molecular markers. [ABSTRACT FROM AUTHOR]

The constant human trait that corresponds to the formal element in art is man's aesthetic sensitivity, prevalently that of the feminine nude. What constitutes a variable is the understanding that the viewer is building through the act of abstraction of his sensorial perceptions. I have tried - through abstract-expressionistic representation - to capture and idealize the nature of the beauty of feminine nudity, so that the reproduction through its form by image should constitute a range of suggestion, whereby reality becomes more sensitive, thereby helping the viewer understand it and enjoy the importance of its beauty and its eternal charm. [ABSTRACT FROM AUTHOR]