Evidence Of Positive Assortative Mating Research Articles

Patterns of Genetic Diversity and Mating Systems in a Mass-Reared Black Soldier Fly Colony.

The black soldier fly (BSF), Hermetia illucens, is a promising candidate for the emerging insect farming industry with favourable characteristics for both bioremediation and production of animal delivered nutritive and industrial compounds. The genetic management of commercial colonies will become increasingly important for the sustainability of the industry. However, r-selected life history traits of insects pose challenges to conventional animal husbandry and breeding approaches. In this study, the long-term genetic effects of mass-rearing were evaluated as well as mating systems in the species to establish factors that might influence genetic diversity, and by implication fitness and productivity in commercial colonies. Population genetic parameters, based on microsatellite markers, were estimated and compared amongst two temporal wild sampling populations and four generations (F28, F48, F52, and F62) of a mass-reared colony. Furthermore, genetic relationships amongst mate pairs were evaluated and parentage analysis was performed to determine the oc-currence of preferential mate choice and multiple paternity. The mass-reared colony showed a reduction in genetic diversity and evidence for inbreeding with significant successive generational genetic differentiation from the wild progenitor population. Population-level analysis also gave the first tentative evidence of positive assortative mating and genetic polyandry in BSF. The homoge-neity of the mass-reared colony seems to result from a dual action caused by small effective popu-lation size and increased homozygosity due to positive assortative mating. However, the high ge-netic diversity in the wild and a polyandrous mating system might suggest the possible restoration of diversity in mass-reared colonies through augmentation with the wild population.

Female and male plumage color is linked to parental quality, pairing, and extrapair mating in a tropical passerine

AbstractSexual selection has been proposed to drive the evolution of elaborate phenotypic traits in males, which often confer success in competition or mating. However, in many species, both males and females display such traits. Studies examining how selection acts on both sexes are scarce. In this study, we investigated whether plumage ornamentation is sexually selected in females and males lovely fairy-wren Malurus amabilis, a cooperatively breeding songbird. We found that female and male plumage color was correlated with parental quality but not with individual quality or survival. We also found evidence of positive assortative mating based on plumage color. Microsatellite analyses of paternity indicated that the lovely fairy-wren has high levels of extrapair paternity (EPP), with 53% of offspring (in 58% of broods of 57% of females) resulting from extrapair (EP) mating. Female and male plumage color did not predict reproductive success or the proportion of EP offspring in their own nest, but less colorful males obtained higher EPP when paired with more colorful females and gained overall higher total paternity (own nest and other nests). We argue that plumage color may be under sex-specific selection, highlighting the importance of looking at both sexes in studies of sexual selection and ornament evolution. The current findings together with the previous study suggest that plumage color in female and male lovely fairy-wrens appears to be an honest signal relevant in both intrasexual and intersexual competition contexts.

Sexing a Monomorphic Plumage Seabird Using Morphometrics and Assortative Mating

This study aimed to establish a reliable method based on morphometrics to sex Long-tailed Jaeger (Stercorarius longicaudus), a species with slight differences in body size between sexes but no plumage differences. The presence of assortative mating based on size was also examined to determine if within-pair differences in size could improve sexing. Seventy-six Long-tailed Jaegers were measured, including 26 breeding pairs, on Bylot Island (Nunavut, Canada) during summers 2014-2018. Bird weight, wing chord, tarsus, head, and tail feathers were measured, and breast feathers were collected to determine sex with DNA extracts. A first discriminant function based on two variables (body mass and wing chord) accurately sexed 83% of birds. Some evidence for positive assortative mating based on size was found, as body mass of pair members was positively related, and 88% of females were heavier than their partner. A second discriminant function that included body mass, wing chord, length of the central tail feather, and partner's body mass accurately sexed 92% of birds. Adding a new morphometric and information from the partner allowed a reduction in sex misclassification by half (17% vs. 8%). In conclusion, external body measurements are useful to sex Long-tailed Jaegers, a slightly dimorphic species, and measurements of both members of a pair considerably improve the accuracy of sexing, likely due to the presence of assortative mating.

No evidence of positive assortative mating for genetic quality in fruit flies.

In sexual populations, the effectiveness of selection will depend on how gametes combine with respect to genetic quality. If gametes with deleterious alleles are likely to combine with one another, deleterious genetic variation can be more easily purged by selection. Assortative mating, where there is a positive correlation between parents in a phenotype of interest such as body size, is often observed in nature, but does not necessarily reveal how gametes ultimately combine with respect to genetic quality itself. We manipulated genetic quality in fruit fly populations using an inbreeding scheme designed to provide an unbiased measure of mating patterns. While inbred flies had substantially reduced reproductive success, their gametes did not combine with those of other inbred flies more often than expected by chance, indicating a lack of positive assortative mating. Instead, we detected a negative correlation in genetic quality between parents, i.e. disassortative mating, which diminished with age. This pattern is expected to reduce the genetic variance for fitness, diminishing the effectiveness of selection. We discuss how mechanisms of sexual selection could produce a pattern of disassortative mating. Our study highlights that sexual selection has the potential to either increase or decrease genetic load.

Educational Assortative Mating and Household Income Inequality

We investigate the pattern of educational assortative mating, its evolution over time, and its impact on household income inequality. To these ends, we use rich data from the United States and Norway over the period 1980-2007. We find evidence of positive assortative mating at all levels of education in both countries. However, the time trends vary by the level of education: Among college graduates, assortative mating has been declining over time, whereas individuals with a low level of education are increasingly sorting into internally homogenous marriages. When looking within the group of college educated, we find strong but declining assortative mating by academic major. These findings motivate and guide a decomposition analysis, where we quantify the contribution of various factors to the distribution of household income. We find that educational assortative mating accounts for a non-negligible part of the cross-sectional inequality in household income. However, changes in assortative mating over time barely move the time trends in household income inequality. The reason is that the decline in assortative mating among the highly educated is offset by an increase in assortative mating among the less educated. By comparison, increases in the returns to education over time generate a considerable rise in household income inequality, but these price effects are partly mitigated by increases in college attendance and completion rates among women.

Sexual size dimorphism and discriminant functions for predicting the sex of Atlantic Puffins (Fratercula arctica)

Assortative mating is an important aspect of mate choice, especially in species where both sexes express ornamentation. Such ornaments could function as signals of individual quality and could result in individuals mating with partners of similar quality. We tested for assortative mating by measuring 63 pairs of Atlantic Puffins (Fratercula arctica) at two Canadian colonies (Gull Island, Witless Bay, Newfoundland and Labrador; and Machias Seal Island, New Brunswick), and constructed a function to predict the sex of puffins from Witless Bay. Male and female puffins have similar plumage, and both sexes have fleshy rosettes at the base of their bill, which are supposedly ornaments. We also examined changes in measurements over time in 5–30-year-old puffins recaptured at Machias Seal Island. Our discriminant function correctly predicted the sex of 88 % of puffins from Witless Bay. Overall, males were larger than females in all measurements, but within pairs, some females were larger in 4–27 % of individual measurements. We found no evidence of positive assortative mating or of assortative mating by rosette size, and rosette area did not increase with age. The importance of puffins’ rosettes as indicators of quality requires further investigation.

Size does not matter for male Marbled Salamanders (Ambystoma opacum)

Understanding the phenotypic attributes that contribute to variance in mating and reproductive success is crucial in the study of evolution by sexual selection. In many animals, body size is an important trait because larger individuals enjoy greater fitness due to the ability to secure more mates and produce more offspring. Among males, this outcome is largely mediated by greater success in competition with rival males and (or) advantages in attractiveness to females. Here we tested the hypothesis that large male Marbled Salamanders (Ambystoma opacum (Gravenhorst, 1807)) mate with more females and produce more offspring than small males. In experimental breeding groups, we included males chosen specifically to represent a range of sizes. After gravid females mated and nested freely, we collected egg clutches and genotyped all adults and samples of hatchlings with highly variable microsatellite markers to assign paternity. Size had little effect on male mating and reproductive success. Breeding males were not bigger than nonbreeding males, mates of polyandrous females were not smaller than those of monogamous females, and there was no evidence for positive assortative mating by size. Although body size did not matter for male Marbled Salamanders, we documented considerable fitness variation and discuss alternative traits that could be undergoing sexual selection.

Feather-chewing lice and Tree Swallow biology

ABSTRACT Feather-chewing lice (Order Phthiraptera, Suborder Ischnocera) commonly infest birds and may affect their survival and reproduction. From 1993 to 2005, we examined several aspects of the biology of breeding Tree Swallows (Tachycineta bicolor) potentially associated with holes in wing and tail feathers caused by feather-chewing lice. Most individuals had <10 feather holes, but 90% of second-year (SY) females, 68% of after-second-year (ASY) females, and 80% of males had ≥1 feather hole. ASY females had significantly fewer feather holes than SY females and males. There was evidence of positive assortative mating for feather hole number between ASY females and their mates. SY females and their mates did not differ significantly in the number of feather holes, but ASY females had significantly fewer holes than their mates. Males with fewer feather holes were heavier and had longer right wings. Feather hole abundance was not significantly associated with reproductive performance. Feather hole abundance...

Le rôle de l’héritage et du revenu du travail dans les choix matrimoniaux

Cet article etudie l’importance du patrimoine herite dans les choix matrimoniaux en France. A partir des enquetes Actifs financiers et Patrimoine, nous utilisons l’information disponible sur le patrimoine parental afin d’estimer le patrimoine herite espere des individus tout au long de leur vie, ce qui permet d’etudier le patrimoine herite total. Nous montrons qu’il existe une similarite des conjoints du point de vue du patrimoine herite. De plus, il est tres improbable pour une personne n’ayant pas recu d’heritage d’epouser un riche heritier (ou une riche heritiere). Alors que l’education explique la majeure partie de l’homogamie en termes de revenu permanent, elle explique seulement 20 % de la correlation du patrimoine herite. Enfin, nous mettons en evidence une faible substituabilite entre heritage et revenus du travail. Ces derniers ne compensent que partiellement un manque de richesse parentale. Nos estimations font etat d’un degre d’homogamie relativement stable entre 1992 et 2010. Le degre de substituabilite augmente quant a lui legerement a la fin de la periode d’etude. Deux mecanismes peuvent expliquer ces resultats : le processus de socialisation et l’effet des preferences. Ces nouveaux resultats sont determinants pour comprendre la dynamique des inegalites et plus particulierement les consequences de l’evolution a long terme de l’heritage dans les pays riches.

Educational Assortative Mating and Household Income Inequality

We document the degree of educational assortative mating, how it evolves over time, and the extent to which it differs between countries. Our analysis focuses on the United States but also uses data from Denmark, Germany, the United Kingdom, and Norway. We find evidence of positive assortative mating at all levels of education in each country. However, the time trends vary by the level of education: Among college graduates, assortative mating has been declining over time, whereas individuals with a low level of education are increasingly sorting into internally homogeneous marriages. These findings motivate and guide a decomposition analysis, where we quantify the contribution of various factors to the distribution of household income. We find that educational assortative mating accounts for a non-negligible part of the cross-sectional inequality in household income in each country. However, changes in assortative mating over time barely move the time trends in household income inequality. This is because the inequality contribution from the increase in assortative mating among those with lower levels of education is offset by the equalizing effect from the decline in assortative mating among the highly educated. By comparison, increases over time in the returns to education generate a considerable rise in household income inequality, but these price effects are partly mitigated by increases in college attendance and completion rates among women.

Short stature in African pygmies is not explained by sexual selection

African pygmies' short stature has been studied for more than a century, but the evolution of this extreme phenotype remains unknown. The present study tests the hypothesis that sexual selection, through preference for short partners, may have contributed to the evolution of pygmies' stature. We gathered anthropometric and familial data from 72 Baka pygmy couples and 27 neighboring Nzimé nonpygmy couples from Cameroon. We found evidence for positive assortative mating and partial evidence for the male-taller norm in both groups. This is surprisingly close to results reported for many modern occidental populations, in which sexual selection is thought to exert a positive selective pressure on men height. Semistructured interviews of Baka pygmies concerning height and mate choice suggested that the male-taller norm matches mating preferences. Stature was also positively correlated with the number of serial marriages contracted by men of both populations, while the stature of women was not related to their mating success. Finally, we did not detect any linear or quadratic effect of height on reproductive success for either men or women. Altogether, our results demonstrate that stature influences mate choice in pygmies, and we argue that, if of any influence for sexual selection, mate choice should have favored tallness rather than shortness in our pygmy population. Consequently, this study establishes that sexual selection is a very unlikely candidate to account for the evolution of pygmies' short stature.

The Chelidonura tsurugensis–sandrana (Gastropoda: Cephalaspidea) species complex: do reproductive decisions maintain colour polymorphism?

Cephalaspid gastropod molluscs are increasingly being utilized in studies of tradeoffs associated with conflicts in simultaneous hermaphroditic reproduction. Chelidonura sandrana exhibits a wide range of colour forms, from black to yellow-spotted or marked with white. One of these colour morphs was described as Chelidonura tsurugensis Baba & Abe, 1959, while others have been accepted as natural variation within C. sandrana Rudman, 1973. Previous work has mostly assumed (1) that colour forms represent the same species and (2) that reproductive behaviour does not differ among colour forms. Mating behaviour between three co-occurring colour forms (simplified to ‘black’, ‘yellow’ and ‘white’) of the Chelidonura tsurugensis–sandrana species complex was investigated to test the above assumptions. Individuals of each colour form were crossed with individuals of the same form, and then with each of the two other colour forms, and with additional species as controls. Mating frequency, duration and an individual’s role of sperm donor or receiver were recorded. The results show that there was no evidence for positive assortative mating with respect to colour form. Instead, at least one colour form was shown to mate significantly more often, and for longer, with individuals of colour forms other than its own. There was no evidence for trading of intromissions or intromission duration among colour forms. Although all three colour forms readily mate and behave like a single biological species, the questionable identity of C. tsurugensis prevents synonymization of C. sandrana with this species. Conservatively, we suggest that until a systematic revision of Chelidonura is carried out, the application of the name C. tsurugensis should be restricted to Japan, and elsewhere the yellow-spotted colour form should be referred to as C. sandrana.

Maintenance of a hybrid zone: The role of female mate choice

ABSTRACT. Hybrid zones between different plumage morphs are common in birds. These zones can be maintained by (1) divergent selection pressures on either side of the zone or (2) some restriction to mating between the forms that limits gene flow from one side to the other. In eastern Australia, there is a distinct hybrid zone between two plumage forms of the Australian Magpie (Cracticus tibicen), with black-backed birds in the north, white-backed birds in the south, and both forms plus intermediates in a zone ∼100 km wide. On the basis of social groups, there is no evidence of assortative mating in the hybrid zone. However, extrapair fertilizations (EPF) occur in other Australian Magpie populations and, thus, may also occur in the hybrid zone. We examined evidence of EPFs in the hybrid zone to test for either (1) positive assortative mating or (2) preference for the brighter plumage form. Although there were significant levels of EPFs of ∼30%, there was no evidence for positive assortative mating or prefer...

Ethnic intermarriage among immigrants: human capital and assortative mating

This paper analyzes the determinants of interethnic marriages by immigrants in the United States. The dependent variable is intermarriage across ethnic groups (on the basis of ancestry and country of birth) and the inclusion of the explanatory variables is justified by a simple rational choice economic model. A binomial logistic regression is estimated using data from the 1980 US Census, the last Census where post-migration marriages can be identified. Results show that the probability of intermarriage increases the longer a migrant resides in the U.S. and the younger the age at arrival. Both relationships can be attributable to the accumulation of US-specific human capital and an erosion of ethnic-specific human capital. Inter-ethnic marriages are more likely between individuals with similar education levels, providing evidence of positive assortative mating by education for immigrants. The construction of the “availability ratio” for potential spouses from one’s own group and group size where one lives using data from several Censuses provides a the measure of the marriage market. Intermarriage is lower the greater the availability ratio and the larger the size of one’s own group. Linguistic distance of the immigrant’s mother tongue from English indirectly measures the effect of English language proficiency at arrival and is found to be a significant negative predictor of intermarriage. Those who report multiple ancestries and who were previously married are more likely to intermarry.

Sexual Selection and the Random Union of Gametes: Testing for a Correlation in Fitness between Mates inDrosophila melanogaster

Both males and females vary in fitness. While high-fitness males typically have greater siring success, it is not clear whether these males sire an equal fraction of offspring from all females or a disproportionately large fraction with high-fitness females. The latter nonrandom reproductive pattern can arise as the result of sexual selection and creates a positive correlation in fitness between mates. Such a correlation, if it reflects a positive genetic correlation between mates with respect to fitness, increases the efficiency of selection, reducing mutation load and speeding adaptation. While there is evidence from many taxa that assortative mating for fitness may occur, these studies typically focus on observed matings rather than realized reproductive output. Here, we examine assortative mating for fitness in Drosophila melanogaster, first in the context of virgin matings and then using a measure of realized reproduction that incorporates remating and postcopulatory processes. We find evidence for positive assortative mating among virgins but no evidence of assortative mating using the more complete measure of reproduction.

Ethnic Intermarriage Among Immigrants: Human Capital and Assortative Mating

This paper analyzes the determinants of interethnic marriages by immigrants in the United States. The dependent variable is intermarriage across ethnic groups (on the basis of ancestry and country of birth) and the inclusion of the explanatory variables is justified by a simple rational choice economic model. A binomial logistic regression is estimated using data from the 1980 US Census, the last Census where post-migration marriages can be identified. Results show that the probability of intermarriage increases the longer a migrant resides in the U.S. and the younger the age at arrival. Both relationships can be attributable to the accumulation of US-specific human capital and an erosion of ethnic-specific human capital. Inter-ethnic marriages are more likely between individuals with similar education levels, providing evidence of positive assortative mating by education for immigrants. The construction of the availability ratio for potential spouses from one’s own group and group size using data from several Censuses provides a more accurate measure of the marriage market. Intermarriage is lower the greater the availability ratio and the larger the size of one’s own group. Linguistic distance of the immigrant’s mother tongue from English indirectly measures the effect of English language ability at arrival and is found to be a significant negative predictor of intermarriage. Those who report multiple ancestries and who were previously married are more likely to intermarry.

Sexual Dimorphism, Female-Female Pairs, and Test for Assortative Mating in Common Terns

We trapped 656 Common Terns (Sterna hirundo) and measured five body dimensions and body mass for each bird; 313 birds were of known age, and 229 were sexed by DNA. Males were larger than females in all five dimensions, but were smaller in body mass. Early-nesting birds were larger than late-nesting birds in all five dimensions: at least for wing length, this difference was related to both laying date and age. Head length (from back of skull to tip of bill) was the most useful measure for sexing Common Terns in the field. Discriminant functions indicated that 75.9% of single birds and 84.5% of pairs could be sexed correctly by head length alone. We present rules and nomograms for field sexing of Common Terns; these provide trade-offs between sensitivity (proportion of birds classified) and specificity (proportion of birds correctly sexed). Three of 80 pairs (4%) included two females: these pairs nested early and were at least as successful as male-female pairs. Within pairs, tarsus lengths were negatively correlated; we found no evidence for positive assortative mating by linear dimensions or body mass. This study confirms some previous reports of sexual dimorphism in this species based on less reliable methods of sexing, but fails to confirm other reports of sexual dimorphism and assortative mating.

Species and Populations of the &lt;I&gt;Anopheles gambiae&lt;/I&gt; Complex in Cameroon with Special Emphasis on Chromosomal and Molecular Forms of &lt;I&gt;Anopheles gambiae&lt;/I&gt; s.s.

We studied the geographical distribution of species, chromosomal, and molecular forms of the Anopheles gambiae Giles (Diptera: Culicidae) complex in 23 sites in Cameroon, Central Africa. Almost all the specimens collected in the four northern-most arid sites were Anopheles arabiensis. Anopheles melas was found in a rural locality surrounded by mangrove swamps, on the Atlantic Coast. In total, 1,525 An. gambiae s.s. females were identified down to their molecular form, and inversion polymorphisms on polytene chromosomes were scored from 186 half-gravid females. The Forest chromosomal form, with standard arrangements almost fixed on both arms of chromosome-2, was the only one observed in the southern, more humid localities. Karyotypes typical of Savanna and Mopti were recorded northwards, in the humid savannas of the Adamawa Province. The molecular forms M and S were widespread throughout Cameroon, and assort independently from the chromosomal forms. S-form populations were characterized by karyotypes typical of Forest and Savanna chromosomal forms, and M-form populations were characterized by karyotypes typical of Forest, Savanna, and Mopti. No M/S hybrid patterns were detected, although M and S mosquitoes were sympatric in 15 sites, providing further evidence for positive assortative mating within molecular forms. The observed ecogeographical distribution of M and S was peculiar: the ecological parameters involved in this distribution still need to be clarified as well as the possible role of competitive exclusion between chromosomally homosequential molecular forms. No difference was observed in host preference or in Plasmodium falciparum infection rates between sympatric M and S populations.

Species and Populations of theAnopheles gambiaeComplex in Cameroon with Special Emphasis on Chromosomal and Molecular Forms ofAnopheles gambiaes.s.

We studied the geographical distribution of species, chromosomal, and molecular forms of the Anopheles gambiae Giles (Diptera: Culicidae) complex in 23 sites in Cameroon, Central Africa. Almost all the specimens collected in the four northern-most arid sites were Anopheles arabiensis. Anopheles melas was found in a rural locality surrounded by mangrove swamps, on the Atlantic Coast. In total, 1,525 An. gambiae s.s. females were identified down to their molecular form, and inversion polymorphisms on polytene chromosomes were scored from 186 half-gravid females. The Forest chromosomal form, with standard arrangements almost fixed on both arms of chromosome-2, was the only one observed in the southern, more humid localities. Karyotypes typical of Savanna and Mopti were recorded northwards, in the humid savannas of the Adamawa Province. The molecular forms M and S were widespread throughout Cameroon, and assort independently from the chromosomal forms. S-form populations were characterized by karyotypes typical of Forest and Savanna chromosomal forms, and M-form populations were characterized by karyotypes typical of Forest, Savanna, and Mopti. No M/S hybrid patterns were detected, although M and S mosquitoes were sympatric in 15 sites, providing further evidence for positive assortative mating within molecular forms. The observed ecogeographical distribution of M and S was peculiar: the ecological parameters involved in this distribution still need to be clarified as well as the possible role of competitive exclusion between chromosomally homosequential molecular forms. No difference was observed in host preference or in Plasmodium falciparum infection rates between sympatric M and S populations.

Testing the ‘assortative mating’ hypothesis on a variation maintenance mechanism for flowering time within a forest‐floor population of Primula sieboldii

AbstractFlowering phenology and allozyme variation were studied to test the existence of positive assortative mating for flowering time in a natural population of Primula sieboldii E. Morren, a heterostylous perennial herb, consisting of approximately 180 genets in a deciduous forest. There was significant variation in flowering date among genets, but not between heterostylous morphs. The temporal order of the flowering time of genets was fairly constant for the two years of the study. The spatial heterogeneity of light availability at the study site was small during the flowering season of the species. In order to analyze the extent of genetic differentiation between early‐ and late‐flowering genet groups, allozyme diversities were analyzed with 10 loci. The GST between the early‐ and late‐flowering groups was not significantly different from zero. Evidence of positive assortative mating for flowering time was not detected. Prolongation of flowering duration due to pollen limitation may be one important factor preventing the genetic differentiation of early‐ and late‐flowering groups by enhancing the overlap of flowering time among genets.