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With limited sampling, geographic variation within a single species can be difficult to distinguish from interspecific variation, confounding our ability to draw accurate species boundaries. We argue that thorough sampling and analysis of contact zones between putative taxa can determine if assortative mating or selection against hybrids exists (supporting the presence of two distinct species), or alternatively if mating is random among genotypes and admixture among adjacent populations is gradual and continuous (supporting geographic variation within a single species). Here, we test two alternative hypotheses for two pairs of named taxa at contact zones within the American milksnake (Lampropeltis triangulum) complex. A prior morphological analysis found areas of gradual intergradation among named taxa, and concluded that the taxa represented geographical races of a single polytypic species. In contrast, a subsequent analysis of gene sequence data, but with limited sampling near the contact zones, hypothesized distinct boundaries between species at the contact zones. At the contact zone between proposed species L. triangulum and Lampropeltis gentilis , we examined a |$\sim$| 700 km-wide transect across the states of Kansas and Missouri, with thorough sampling and reduced-representation genomic-level sequencing, to test the two opposing taxonomic hypotheses. Our transect analyses included examinations of population structure, fixed differences, cline-fitting, and an admixture index analysis. These analyses all supported a gradual and continuous geographic cline across a broad intergrade zone between two geographic forms of L. triangulum , thus providing strong support for a single species in this region (and no support for the recognition of L. gentilis as a distinct species). At a second contact zone between proposed species L. triangulum and Lampropeltis elapsoides (but variously treated as species or subspecies by different researchers) in Kentucky and Tennessee, we re-evaluated morphological data. In this case, the contact zone analysis indicated sympatry and reproductive isolation of the two taxa, and thus strongly supported L. triangulum and L. elapsoides as distinct species. We conclude that detailed studies of contact zones, based on either genetic or morphological data, are essential for distinguishing intraspecific from interspecific variation in the case of widely and continuously distributed taxa. [Contact zones; speciation; species concepts; species delimitation; taxonomy.] [ABSTRACT FROM AUTHOR]

Quantitative models that simulate the inheritance and evolution of fitness‐linked traits offer a method for predicting how environmental or anthropogenic perturbations can affect the dynamics of wild populations. Random mating between individuals within populations is a key assumption of many such models used in conservation and management to predict the impacts of proposed management or conservation actions. However, recent evidence suggests that non‐random mating may be underestimated in wild populations and play an important role in diversity‐stability relationships. Here we introduce a novel individual‐based quantitative genetic model that incorporates assortative mating for reproductive timing, a defining attribute of many aggregate breeding species. We demonstrate the utility of this framework by simulating a generalized salmonid lifecycle, varying input parameters, and comparing model outputs to theoretical expectations for several eco‐evolutionary, population dynamic scenarios. Simulations with assortative mating systems resulted in more resilient and productive populations than those that were randomly mating. In accordance with established ecological and evolutionary theory, we also found that decreasing the magnitude of trait correlations, environmental variability, and strength of selection each had a positive effect on population growth. Our model is constructed in a modular framework so that future components can be easily added to address pressing issues such as the effects of supportive breeding, variable age structure, differential selection by sex or age, and fishery interactions on population growth and resilience. With code published in a public Github repository, model outputs may easily be tailored to specific study systems by parameterizing with empirically generated values from long‐term ecological monitoring programs. [ABSTRACT FROM AUTHOR]

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Given the ever-increasing economic and social ties with the Mainland, Hong Kong-Mainland cross-border marriage patterns experienced significant changes after the handover. The proportion of cross-border marriages only accounted for 2% of marriages registered in Hong Kong in the pre-handover period but jumped to 34.7% after the handover. This study examines the impact of stronger economic ties and weakened social and cultural boundaries on the patterns of assortative mating in cross-border marriages. As most of the cross-border workers from Hong Kong are males, they have increasing opportunities for social interaction with Mainland women in communities and social circles in the Mainland. After the handover, the language skills of residents on both sides showed significant improvement and this can enhance the possibility of finding a marriage partner across the border. Empirical results suggest a weaker positive assortative mating in respect of age and educational attainment among Hong Kong husband-Mainland wife couples after the handover. Previous studies suggest that marital partner selection reflects the strength of social boundaries and the strength of these boundaries should be stronger for cross-border marriages. The results of this paper support the view that stronger economic ties and weakened social and cultural boundaries do promote cross-border marriages and negative assortative mating in these marriages. [ABSTRACT FROM AUTHOR]

The evolutionary trajectories and genetic architectures underlying ecological divergence with gene flow are poorly understood. Sympatric timing types of the intertidal insect Clunio marinus (Diptera) from Roscoff (France) differ in lunar reproductive timing. One type reproduces at full moon, the other at new moon, controlled by a circalunar clock of yet unknown molecular nature. Lunar reproductive timing is a magic trait for a sympatric speciation process, as it is both ecologically relevant and entails assortative mating. Here, we show that the difference in reproductive timing is controlled by at least four quantitative trait loci (QTL) on three different chromosomes. They are partly associated with complex inversions, but differentiation of the inversion haplotypes cannot explain the different phenotypes. The most differentiated locus in the entire genome, with QTL support, is the period locus, implying that this gene could not only be involved in circadian timing but also in lunar timing. Our data indicate that magic traits can be based on an oligogenic architecture and can be maintained by selection on several unlinked loci. [ABSTRACT FROM AUTHOR]

Multifactorial evolution algorithm (MFEA) is a powerful search paradigm with the purpose of addressing multiple optimization tasks simultaneously in the field of evolutionary computation. The assortative mating of MFEA is a key component to make it outperform traditional single-task optimization algorithms. However, the optimal solution of each generation has still not been well utilized to accelerate convergence in the process of assortative mating operation for existing MFEAs. This paper proposes a multifactorial differential evolution algorithm with optima-based transformation (MFDE-OBT), which employs the optimal solution of each generation to design an improved assortative mating operation based on the DE/rand/2 mutation. The improved operation generates an offspring for each individual by running a perturbation around a current optimal individual. The object of the assortative mating is a vector added for the perturbation, which is the sum of two difference vectors generated by a random sample with a certain probability from an individual set that can be same as or different from the one of the task involving the optimal individual. In addition, MFDE-OBT integrates an opposition-based search strategy behind the assortative mating operation to balance exploitation and exploration of each search space. Experimental results on benchmark problems constituted by tasks with different degree of similarity and intersection demonstrate the advantage of the proposed MFDE-OBT algorithm over some state-of-the-art algorithms, in terms of solution precision and convergence performance. [ABSTRACT FROM AUTHOR]

Mating behavior can play a key role in speciation by inhibiting or facilitating gene flow between closely related taxa. Hybrid zones facilitate a direct examination of mating behavior and the traits involved in establishing species barriers. The long‐tailed finch (Poephila acuticauda) has two hybridizing subspecies that differ in bill color (red and yellow), and the yellow bill phenotype appears to have introgressed ~350 km eastward following secondary contact. To examine the role of mate choice on bill color introgression, we performed behavioral assays using natural and manipulated bill colors. We found an assortative female mating preference for males of their own subspecies when bill color was not manipulated. However, we did not find this assortative preference in trials based on artificially manipulated bill color. This could suggest that assortative preference is not fixed entirely on bill color and instead may be based on a different trait (e.g., song) or a combination of traits, or alternatively may be due to lower statistical power alongside the bill manipulations being unconvincing to the female choosers. Intriguingly, we find a bias in the inheritance of bill color in captive bred F1 hybrid females. Previous modeling suggests that assortative mate preference and this kind of partial dominance in the underlying genes may together contribute to introgression, making the genetic architecture of bill color in this system a priority for future research. [ABSTRACT FROM AUTHOR]

The negative consequences of inbreeding have led animal biologists to assume that mate choice is generally biased against relatives. However, inbreeding avoidance is highly variable and by no means the rule across animal taxa. Even when inbreeding is costly, there are numerous examples of animals failing to avoid inbreeding or even preferring to mate with close kin. We argue that selective and mechanistic constraints interact to limit the evolution of inbreeding avoidance, notably when there is a risk of mating with heterospecifics and losing fitness through hybridization. Further, balancing inbreeding avoidance with conspecific mate preference may drive the evolution of multivariate sexual communication. Studying different social and sexual decisions within the same species can illuminate trade-offs among mate-choice mechanisms. Individuals often mate with relatives, even when it is costly: the 'inbreeding paradox'. Avoiding kin shares neural and molecular mechanisms with other social tasks, such as affiliative behavior and conspecific mate preference. 'Active' inbreeding avoidance battles against nonsexual kin affiliation. Trade-offs between conspecific preference and inbreeding avoidance may constrain or facilitate hybridization. [ABSTRACT FROM AUTHOR]

Assortative mating is non‐random mating by the mutual choice of phenotypes or behavioral types. In polygynandrous species, competition for mating by social rank can lead to assortative mating. However, although not an individual trait, social bonds also influence mating opportunities resembling assortative mating. Stump‐tailed macaques form long‐term close bonds and organize in a linear dominance–subordination hierarchy. Therefore, we studied whether the strength of the social bond and rank closeness influenced mating decisions and increased mating opportunities, particularly for low‐ and middle‐ranking animals. Firstly, we observed whether females directed proceptive behavior to close‐bonded or adjacent rank males. Secondly, we measured whether successful copulations were related to the strength of social bonds and close ranking. Thirdly, to ensure that copulations owed mainly to the aforementioned factors, we also evaluated whether sexual coercion was unrelated to social bonds and rank similarities. Finally, we assessed whether close bonds mediated agonistic support to females. The study subjects were 12 adult female and 11 male captive stump‐tailed macaques. We monitored daily females' reproductive status by vaginal cytology. Sexual behavior was recorded by all occurrences sampling and scan sampling to collect the agonistic and affiliative instances required to calculate social ranks, social bond strength, and agonistic support. The results indicated that the probability of females displaying proceptivity increased during the follicular phase toward close‐bonded and high‐ranking males. Copulation chances increased with male–female social bonds and rank closeness. Forced copulation decreased in close‐bonded individuals, while agonistic support increased in close‐ranking strong‐bonded animals. In conclusion, close social bonds and similar social rank result in non‐random mating in stump‐tailed macaques. [ABSTRACT FROM AUTHOR]

Sex-biased admixture can be inferred from ancestry-specific proportions of X chromosome and autosomes. In a paper published in the American Journal of Human Genetics , Micheletti et al. 1 used this approach to quantify male and female contributions following the transatlantic slave trade. Using a large dataset from 23andMe, they concluded that African and European contributions to gene pools in the Americas were much more sex biased than previously thought. We show that the reported extreme sex-specific contributions can be attributed to unassigned genetic ancestry as well as the limitations of simple models of sex-biased admixture. Unassigned ancestry proportions in the study by Micheletti et al. ranged from ∼1% to 21%, depending on the type of chromosome and geographic region. A sensitivity analysis illustrates how this unassigned ancestry can create false patterns of sex bias and that mathematical models are highly sensitive to slight sampling errors when inferring mean ancestry proportions, making confidence intervals necessary. Thus, unassigned ancestry and the sensitivity of the models effectively prohibit the interpretation of estimated sex biases for many geographic regions in Micheletti et al. Furthermore, Micheletti et al. assumed models of a single admixture event. Using simulations, we find that violations of demographic assumptions, such as subsequent gene flow and/or sex-specific assortative mating, may have confounded the analyses of Micheletti et al., but unassigned ancestry was likely the more important confounding factor. Our findings underscore the importance of using complete ancestry information, sufficiently large sample sizes, and appropriate models when inferring sex-biased patterns of demography. This Matters Arising paper is in response to Micheletti et al., 1 published in American Journal of Human Genetics. See also the response by Micheletti et al., 2 published in this issue. [ABSTRACT FROM AUTHOR]

Many animals exhibit size assortative mating (SAM), but how predation affects it remains largely unknown. We hypothesized that predation risk may turn prey less choosy, disrupting SAM, or reduce the expected reproductive value of mates, maintaining SAM but with different size ratio between mates. Using a manipulative field experiment, we found that desert isopods under risk of scorpion predation maintained SAM, but that males that choose and fight over females were on average smaller for a given female size. Less pairs were formed in risky sites, but there were no differences in female sizes and progeny number, size and age near and away from scorpion burrows. Our complementary behavioral experiments revealed that bigger males stayed longer near safe burrows, and won more male–male contests than smaller conspecifics. Our findings highlight that prey can anticipate future costs of predation and use this information to assess the expected reproductive value of mates. [ABSTRACT FROM AUTHOR]

When gene flow accompanies speciation, recombination can decouple divergently selected loci and loci conferring reproductive isolation. This barrier to sympatric divergence disappears when assortative mating and disruptive selection involve the same "magic" trait. Although magic traits could be widespread, the relative importance of different types of magic traits to speciation remains unclear. Because body size frequently contributes to host adaptation and assortative mating in plant-feeding insects, we evaluated several magic trait predictions for this trait in a pair of sympatric Neodiprion sawfly species adapted to different pine hosts. A large morphological dataset revealed that sawfly adults from populations and species that use thicker-needled pines are consistently larger than those that use thinner-needled pines. Fitness data from recombinant backcross females revealed that egg size is under divergent selection between the preferred pines. Lastly, mating assays revealed strong size-assortative mating within and between species in three different crosses, with the strongest prezygotic isolation between populations that have the greatest interspecific size differences. Together, our data support body size as a magic trait in pine sawflies and possibly many other plant-feeding insects. Our work also demonstrates how intraspecific variation in morphology and ecology can cause geographic variation in the strength of prezygotic isolation. [ABSTRACT FROM AUTHOR]

Hedrick et al. (2016) (Negative-assortative mating for color in wolves. Evolution , 70, 757–766) reported on "negative-assortative mating for color in wolves" from Yellowstone National Park, the "first documented case of significant negative-assortative mating in mammals." Here I report a logical inconsistency in their population genetic model that effectively imposes selection against some assortatively mating genotype. After pointing out this inconsistency, I derive new expressions for the frequency of different matings and the equilibrium allele frequencies. Compared to Hedrick et al. (2016) (Negative-assortative mating for color in wolves. Evolution , 70, 757–766), the system rapidly approaches an equilibrium based on observed levels of negative-assortative mating in this population. Hence, the revised model may strengthen the case that assortative mating can maintain polymorphism and provides logically consistent results to inform the study of nonrandom mating in other organisms. [ABSTRACT FROM AUTHOR]

The 'dark triad' represents the socially aversive personality traits of Machiavellianism, subclinical narcissism (henceforth, 'narcissim'), and subclinical psychopathy (henceforth, 'psychopathy'). There is evidence of assortative mating suggesting romantic partners are more similar than chance for these traits at the start of relationships (initial assortment) and not becoming alike with time (convergence), that people seek out partners to whom they are similar (active assortment), and that partner resemblance is not explained by social stratification processes (social homogamy). As the literature relates primarily to Eastern European and North American populations, we present studies from the UK (N = 104 couples) and Fiji (N = 99 couples). These showed significant positive assortment for each dark triad trait (other than psychopathy in the Fijian sample), and suggest the effects are explained by initial and active assortment and not by convergence or social homogamy. We also submitted the literature to meta-analytic review (Machiavellianism: k = 10, N = 1302; narcissism: k = 14, N = 1645; psychopathy: k = 13, N = 1989) and observed positive within-couple correlations of small (narcissism, psychopathy) to medium (Machiavellianism) effect size for each of the dark triad traits. • Assortative mating results in greater than chance similarity in romantic partners. • This process may occur for the dark triad of Machiavellianism, subclinical narcissism, and subclinical psychopathy. • Study 1 demonstrates couple similarity for the dark triad in a UK sample. • Study 2 broadly replicates these findings in a sample from Fiji. • Study 3 demonstrates robust couple similarity effects at the meta-analytic level. [ABSTRACT FROM AUTHOR]

Although studies have established that health and socioeconomic disadvantages often accumulate within families, little is known about the extent to which disability is concentrated within certain families and transmitted across generations. We use retrospective information about growing up with parent(s) or sibling(s) with a disability from the 2020 wave of the representative Survey of Health, Impairment and Living Conditions in Denmark (N = 7709). Building on this data and applying a family life course perspective, we examine if growing up with parent(s) and/or sibling(s) with a disability is associated with 1) having a disability oneself, 2) the probability of having a partner with a disability and 3) the occurrence of disability in the next generation. Our findings demonstrate that the odds of having a disability are higher among individuals who grew up with parent(s) and/or sibling(s) with a disability. While the odds of being partnered are not associated with family members' disabilities, we find a positive association between having grown up with parents with a disability and having a partner with a disability. Moreover, having a child with a disability is positively associated with one's own, parents', siblings' and partner's disabilities. We thus conclude that disability is concentrated within certain families and that both intergenerational transmission and assortative mating contribute to this concentration. • Disability is concentrated in certain families. • Assortative mating contributes to disability concentration. • Moreover, disability is transmitted across generations. • Both genetic and behavioral factors can explain concentration of disability. [ABSTRACT FROM AUTHOR]

The document highlights the awards presented at the 54th Annual Meeting of the Behavior Genetics Association in London, United Kingdom. Notable recipients include Lucía de Hoyos and Lukas Schaffer for Outstanding Associate Member Oral Presentation Awards, Hans Fredrik Sunde for the Outstanding Associate Member Poster Presentation Award, Zhaoying Chen and Floris Huider for Rising Star Awards, Rosa Cheesman and Olakunle Oginni for Early Career awards, Dirk Pelt for the Editors' Choice Award, and Eric Turkheimer for the Dobzhansky Founder's Lifetime Achievement Award. The awards recognize significant contributions to the field of behavior genetics from researchers around the world. [Extracted from the article]

We investigate the role of assortative mating in speciation using the sympatric model of Derrida and Higgs. The model explores the idea that genetic differences create incompatibilities between individuals, preventing mating if the number of such differences is too large. Speciation, however, only happens in this mating system if the number of genes is large. Here we show that speciation with small genome sizes can occur if assortative mating is introduced. In our model individuals are represented by three chromosomes: one responsible for reproductive compatibility, one for coding the trait on which assortativity will operate, and a neutral chromosome. Reproduction is possible if individuals are genetically similar with respect to the first chromosome, but among these compatible mating partners, the one with the most similar trait coded by the second chromosome is selected. We show that this type of assortativity facilitates speciation, which can happen with a small number of genes in the first chromosome. Species, classified according to reproductive isolation, dictated by the first chromosome, can display different traits values, as measured by the second and the third chromosomes. Therefore, species can also be identified based on similarity of the neutral trait, which works as a proxy for reproductive isolation. [ABSTRACT FROM AUTHOR]

Recent developments in sexual selection theory suggest that on their own, mate preferences can promote the maintenance of sexual trait diversity. However, how mate preferences constrain the permissiveness of sexual trait diversity in different environmental regimes remains an open question. Here, we examine how a range of mate choice parameters affect the permissiveness of sexual trait polymorphism under several selection regimes. We use the null model of sexual selection and show that environments with strong assortative mating significantly increase the permissiveness of sexual trait polymorphism. We show that for a given change in mate choice parameters, the permissiveness of polymorphism changes more in environments with strong natural selection on sexual traits than in environments with weak selection. Sets of nearly stable polymorphic populations with weak assortative mating are more likely to show accidental divergence in sexual traits than sets of populations with strong assortative mating. The permissiveness of sexual trait polymorphism critically depends upon particular combinations of natural selection and mate choice parameters.

The frequency and asymmetry of mixed-species mating set the initial stage for the ecological and evolutionary implications of hybridization. How such patterns of mixed-species mating, in turn, are influenced by the combination of mate choice errors and relative species abundance remains largely unknown. We develop a mathematical model that generates predictions for how relative species abundances and mate choice errors affect hybridization patterns. When mate choice errors are small (<5%), the highest frequency of hybridization occurs when one of the hybridizing species is at low abundance, but when mate choice errors are high (>5%), the highest hybridization frequency occurs when species occur in equal proportions. Furthermore, females of the less abundant species are overrepresented in mixed-species matings. We compare our theoretical predictions with empirical data on naturally hybridizing Ficedula flycatchers and find that hybridization is highest when the two species occur in equal abundance, implying rather high mate choice errors. We discuss ecological and evolutionary implications of our findings and encourage future work on hybrid zone dynamics that take demographic aspects, such as relative species abundance, into account. [ABSTRACT FROM AUTHOR]

In animal mating systems, individuals obtain fitness benefits by selecting a mate that increases their chance of reproductive success. Among amphibians, it is generally considered that females select males, primarily based on advertisement calls that signal their size, quality or compatibility. Yet, it is becoming increasingly apparent that amphibians exhibit a wide range of mating systems, including those where assortative mating can occur. Herein, we investigated mate selection in the sandpaper frog, Lechriodus fletcheri; an Australian anuran that breeds explosively during discrete periods of rainfall over an extended breeding period. We compared the size and condition of amplecting pairs relative to other potential suitors within the available population of reproductively active adults over 3 consecutive breeding years. We found no relationship between the SVL of amplecting pairs and no effect of SVL on amplecting status of males within pools. Instead, the condition of amplecting pairs was positively correlated, leading to positive assortative mating. While there was a general decline in condition of adult males and females across each season, changes in the temporal availability of better conditioned mates does not account for the assortative mating were found. Males found in amplexus were also generally of poorer condition, which may occur as individuals investing more heavily into higher-signalling effort are more successful in finding a mate but at the expense of maintaining current condition. We propose that both findings could be evidence of active mate choice in an explosive breeding species. Our findings highlight the need to consider mate condition alongside size to detect the presence of assortative mating or non-random mating among explosive breeding amphibians. [ABSTRACT FROM AUTHOR]

Due to their reduced morphology, non-photosynthetic plants have been one of the most challenging groups to delimit to species level. The mycoheterotrophic genus Monotropastrum, with the monotypic species M. humile, has been a particularly taxonomically challenging group, owing to its highly reduced vegetative and root morphology. Using integrative species delimitation, we have focused on Japanese Monotropastrum, with a special focus on an unknown taxon with rosy pink petals and sepals. We investigated its flowering phenology, morphology, molecular identity, and associated fungi. Detailed morphological investigation has indicated that it can be distinguished from M. humile by its rosy pink tepals and sepals that are generally more numerous, elliptic, and constantly appressed to the petals throughout its flowering period, and by its obscure root balls that are unified with the surrounding soil, with root tips that hardly protrude. Based on genome-wide single-nucleotide polymorphisms, molecular data has provided clear genetic differentiation between this unknown taxon and M. humile. Monotropastrum humile and this taxon are associated with different Russula lineages, even when they are sympatric. Based on this multifaceted evidence, we describe this unknown taxon as the new species M. kirishimense. Assortative mating resulting from phenological differences has likely contributed to the persistent sympatry between these two species, with distinct mycorrhizal specificity. [ABSTRACT FROM AUTHOR]

More than 50% of congenital hearing loss is hereditary, in which the majority form is non-syndromic. In this study we estimate the most prevalent pathogenic genetic changes in an Ossetian cohort of patients. This is useful for local public health officials to promote genetic counseling of affected families with regard to high allele frequencies of prevalent pathogenic variants and assortative mating in the community of people with hearing loss. In this study, genetic heterogeneity of hereditary non-syndromic sensorineural hearing loss (NSNHL) in a cohort of 109 patients and an assessment of the frequency of two GJB2 gene pathogenic variants in a cohort of 349 healthy individuals from the populations of the Republic of North Ossetia-Alania (RNO-Alania) were assessed. The molecular genetic cause of NSNHL in the GJB2 gene in RNO-Alania was confirmed in ~30% of the cases, including ~27% in Ossetians. In Russian patients, the most frequent variant is GJB2: c.35delG (~83%). The GJB2:c.358_360delGAG variant was found to be the most frequent among Ossetians (~54%). Two genetic variants in GJB2, c.35delG and c.358_360delGAG, accounted for 91% of GJB2 pathogenic alleles in the Ossetian patients. A search for large genome rearrangements revealed etiological cause in two Ossetian patients, a deletion at the POU3F4 gene locus associated with X-linked hearing loss (type DFNX2). In another Ossetian patient, a biallelic pathogenic variant in the MYO15A gene caused hearing loss type DFNB3 was identified, and in one Russian family a heterozygous MYH14 gene variant associated with dominant NSNHL was found. Thus, the informative value of the diagnosis was ~37% among all patients with NSNHL from RNO-Alania and ~32% among the Ossetians. These estimates correspond to the literature data on the fraction of recessive genetic forms of hearing loss within the affected population. The importance of this study consists not only in the estimation of the most prevalent pathogenic genetic changes in the Ossetian cohort of patients which could be useful for the public health but also in the genetic counselling of the affected families with regard to the high allele frequencies of revealed pathogenic variants as well as to the assortative mating in community of people with hearing loss. [ABSTRACT FROM AUTHOR]

In the last decade, the personality traits of the common vole (Microtus arvalis) have been well described. However, to date, the mechanisms by which they are maintained in vole populations have received only marginal attention. Inspired by a study of mound-building mice, the present study focused on the possible role of assortative mating based on similar personality traits within the breeding pairs. Under laboratory conditions, seven behavioural parameters were evaluated in 63 individuals (34 males, 29 females) during three successive open field (OF) tests: total distance moved, ratio between the inner area distance/total distance moved, grooming, jumping, locomotion, scanning, and latency to the first movement. Five observed behavioural parameters based on duration were reduced to two synthetic parameters using principal component analysis (PCA). Using GLMM, we calculated for each individual the intercepts (considered personality trait) and slopes of random effects in the total distance, ratio of distances, and the scores of two PCA ordination axes. The effect of within-pair differences in intercepts (personality traits similarity) for each tested variable on the number of offspring was then tested using the function for zero-inflated models. A significant negative correlation was obtained only for the personality trait similarity of the total distance moved. This means that the smaller the personality trait difference (higher similarity) of overcoming a distance (locomotor ability) between the parents led to an increased number of offspring. The results are discussed in terms of the parents' fitness strategies under different population densities. [ABSTRACT FROM AUTHOR]

Understanding evolutionary phenomena that involve size assortative mating requires elucidating the generating mechanisms on which assortment is based. Although various mechanisms have been suggested, their relative importance may differ across taxonomic groups. Males selecting for large, fecund females combined with the dominance of large males in the competition for females has been suggested as a major mechanism in specific groups. However, raptors do not appear to conform to this, because the selection for smallness among males (assumed in a theory of reversed sexual size dimorphism) and the selection for largeness among males (assumed in the theory of size assortative mating) are in opposite directions. We studied the assortative mating during a long‐term study of the Ryukyu Scops Owls Otus elegans interpositus. Significant assortative mating was found for culmen length (from the base to the tip of the bill) and wing length (from the bend of the wing to the tip of the longest primary). Statistical control of the spatial and temporal accessibility of potential mates did not affect the assortment. Males with short wings had slightly higher fitness components than those with long wings, and females settling early tended to have small wings. Considering that early‐settling females can preferentially choose their mates, these results suggest that smaller females have an advantage when choosing smaller males with good reproductive performance. Improved flying and hunting ability of smaller individuals may be the background of choosing smaller individuals. We propose that, not passive process like similarity between individuals and their potential mates, but active mate choice for small individuals is an explanation for the assortative mating in this owl. [ABSTRACT FROM AUTHOR]

Apparent cases of sympatric speciation may actually be due to micro-allopatric or micro-parapatric speciation. One way to distinguish between these models is to examine the existence and nature of genomic islands of divergence, wherein divergent DNA segments are interspersed with low-divergence segments. Such islands should be rare or absent under micro-allopatric speciation but common in cases of speciation with gene flow. Sympatric divergence of endemic fishes is known from isolated saline, crater, postglacial, and ancient lakes. Two morphologically distinct cyprinid fishes, Gymnocypris eckloni scoliostomus (GS) and G. eckloni eckloni (GE), in a small glacial lake on the Qinghai–Tibet Plateau, Lake Sunmcuo, match the biogeographic criteria of sympatric speciation. In this study, we examined genome-wide variation in 46 individuals from these two groups. The divergence time between the GS and GE lineages was estimated to be 20–60 Kya. We identified 54 large genomic islands (≥100 kb) of speciation, which accounted for 89.4% of the total length of all genomic islands. These islands harboured divergent genes related to olfactory receptors and olfaction signals that may play important roles in food selection and assortative mating in fishes. Although the genomic islands clearly indicated speciation with gene flow and rejected micro-allopatric speciation, they were too large to support the hypothesis of sympatric speciation. Theoretical and recent empirical studies suggested that continual gene flow in sympatry should give rise to many small genomic islands (as small as a few kilobases in size). Thus, the observed pattern is consistent with the extensive evidence on parapatric speciation, in which adjacent habitats facilitate divergent selection but also permit gene flow during speciation. We suggest that many, if not most, of the reported cases of sympatric speciation are likely to be micro-parapatric speciation. [ABSTRACT FROM AUTHOR]

Assortative mating is a phenomenon in which romantic partners typically resemble each other at a level greater than chance. There is converging evidence that social behaviours are subject to assortative mating, though less is known regarding social cognition. Social functioning requires the ability to identify and understand the mental states of others, i.e., theory of mind. The present study recruited a sample of 102 heterosexual couples via an online survey to test if theory of mind as measured using facial expressions (Reading the Mind in the Eyes Test) or language (Stiller-Dunbar Stories Task) is associated with assortative mating. Results provide evidence of assortative mating for theory of mind via facial expressions, though there was no such effect for theory of mind via language. Assortative mating for theory of mind via facial expressions was not moderated by length of relationship nor by partner similarity in age, educational attainment, or religiosity, all variables relevant to social stratification. This suggests assortative mating for theory of mind via facial expressions is better explained by partners being alike at the start of their relationship (initial assortment) rather than becoming similar through sustained social interaction (convergence), and by people seeking out partners that are like themselves (active assortment) rather than simply pairing with those from similar demographic backgrounds (social homogamy). [ABSTRACT FROM AUTHOR]

Non-random mating plays a key role in speciation and impacts the individual life history. Body size is known to be one of the most important traits on which the mate choice is based. Various patterns of body size preference are known in fish, but they have been studied in a limited number of species. Although the climbing perch (Anabas testudineus) is widespread and well known, a few reports of its spawning are published. Moreover, its breeding has only been described in captivity and in most cases it has been artificially induced with hormonal agents. This paper describes the main features of natural spawning of the climbing perch in aquarium compared to induced spawning. A positive size-assortative mating has been revealed. The mating system of Anabas has been shown to be flexible, presumably ranging from monogamy to polygamy. The results are discussed in the context of the general issue of the adequacy of fish behaviour research methods. [ABSTRACT FROM AUTHOR]

A key phenomenon to gauge the degree of ethnoracial integration is the pattern of assortative mating based on ethnoracial characteristics. However, possibly because of the assumption that class and not race is the relevant factor in the Mexican stratification regime, assortative mating based on ethnoracial characteristics has been an understudied phenomenon in the country. Based on a multidimensional perspective and using a novel national representative survey, we analyze ethnoracial homogamy patterns in Mexico using four dimensions: skin tone, ethnoracial identification, indigenous language, and Mayan surname. For comparative purposes, we also calculate and control for educational homogamy in our analysis. Results indicate that ethnoracial homogamy is significantly different to educational homogamy and that it differs among dimensions: the highest likelihood of ethnoracial homogamy is found in the linguistic dimension and the lowest in the skin tone dimension. Comparatively, ethnoracial identification and Mayan surname have intermediate levels of homogamy. [ABSTRACT FROM AUTHOR]

Research on educational assortative mating has devoted much attention to educational expansion but has been less focused on a concurrent trend of importance: growing differentiation among higher education institutions. In this study, I examine whether the bifurcation between high- and low-tier institutions in the context of high participation in tertiary education may clarify the mixed evidence on educational homogamy trends across countries. I apply log-linear and log-multiplicative models to analyze trends in educational assortative mating in Japan, which is characterized by a clear, widely acknowledged hierarchy of institutional selectivity. I find that the odds of homogamy are higher among graduates of selective universities than among graduates of nonselective universities. Further, assortative mating trends among graduates of selective and nonselective universities have diverged in recent years. This latter finding perhaps reflects that with the more rapid increase in the share of female students enrolled in less selective institutions, their opportunities to "marry up" have decreased. Results point to the importance of the growing heterogeneity of institutional characteristics, which was obscured in earlier studies, for understanding the impact of educational assortative mating on economic inequality. [ABSTRACT FROM AUTHOR]

This paper studies the relationship between education and early marriage by exploiting the 1986 Compulsory Schooling Laws in China. We find that one additional year of schooling decreases the probability of marriage before age 18 by 1.7% points and increases the age at first marriage by 0.734 years. We examine the role of labour market outcomes, marriage traditions, assortative mating, and peer marriage behaviours. We also find evidence that education decreases fertility outcomes and affects the marriage outcomes of the next generation. This suggests that policies aimed at combating early marriage could start with improving children's educational attainment. [ABSTRACT FROM AUTHOR]

The observation of genetic correlations between disparate human traits has been interpreted as evidence of widespread pleiotropy. Here, we introduce cross-trait assortative mating (xAM) as an alternative explanation. We observe that xAM affects many phenotypes and that phenotypic cross-mate correlation estimates are strongly associated with genetic correlation estimates (R2 = 74%). We demonstrate that existing xAM plausibly accounts for substantial fractions of genetic correlation estimates and that previously reported genetic correlation estimates between some pairs of psychiatric disorders are congruent with xAM alone. Finally, we provide evidence for a history of xAM at the genetic level using cross-trait even/odd chromosome polygenic score correlations. Together, our results demonstrate that previous reports have likely overestimated the true genetic similarity between many phenotypes. [ABSTRACT FROM AUTHOR]

Sexual imprinting is widespread in birds and other species but its existence requires explanation. Our results suggest that sexual imprinting leads to speciation in locally‐adapted populations if a neutral mating cue—e.g., novel plumage coloration—arises through mutation. Importantly, the mating cue locus is not linked to adaptation loci. Local adaptation is a necessary precursor to speciation and occurs when evolution results in stable genetic polymorphisms with one allele predominating in some areas while others predominate elsewhere. Here we use a deterministic two‐niche population genetic model to map the set of migration and selection rates for which polymorphic evolutionary outcomes, i.e., local adaptations, can occur. Approximate equations for the boundaries of the set of polymorphic evolutionary outcomes were derived by Bulmer (American Naturalist, 106, 254, 1972), but our results, obtained by deterministic simulation of the evolutionary process, show that one of Bulmer's equations is inaccurate except when the level of dominance is 0.5, and fails if one of the alleles is dominant. Having an accurate map of the set of migration and selection rates for which polymorphic evolutionary outcomes can occur, we then show using the model of Sibly et al. (Ecology and Evolution, 9, 13506, 2019) that local adaptation in all analyzed cases leads to speciation if a new neutral mating cue arises by mutation. We finish by considering how genome sequencing makes possible testing our model and its predictions. [ABSTRACT FROM AUTHOR]

Phenovariant is a pair of populations or species with distinct phenotypes but little to no genetic divergence, which may have resulted from strong assortative mating, hybridization, or incomplete lineage sorting that changes in the phenotype have exceeded the genotype. Previous studies had mainly tackled this issue on small, colourful reef fishes, but little effort has been made to the barely seen and solitary taxa like the morays (family Muraenidae). In the present study, three species pairs of sympatric morays from Taiwanese waters revealed as phenovariant in the mitochondrial cytochrome oxidase I (COI) were examined from the molecular and morphological perspectives, with three dissimilar scenarios discovered: (1) no hybridization was found between the morphologically most distinct Gymnothorax intesi and Gymnothorax neglectus; (2) Gymnothorax kidako bidirectionally hybridized with Gymnothorax prionodon instead of its closely related species Gymnothorax pseudokidako; and (3) frequently bidirectional hybridization and introgression were detected between Gymnothorax pseudothyrsoideus and Gymnothorax reevesii, a species pair that overlapped in all the morphometric and meristic characters. Nevertheless, the principal component analysis indicated that each species pair has evolved significant morphological divergence, further supporting their taxonomic validities. Our results document the natural hybridization of marine eel taxa for the first time and reveal a diverse evolutionary process among the morays. [ABSTRACT FROM AUTHOR]

Aim: Lanternfishes (Myctophidae) are one of the most species‐rich families of mid‐water fishes. They inhabit the mesopelagic zone, where physical barriers to dispersal and gene flow are permeable. Thus, modes of speciation that rely exclusively on geographical separation are potentially of less importance than those that rely more prominently on evolution of assortative mating through divergent habitat use and/or sexual signals, including visual signals from bioluminescent light organs. Here we used phylogenetic, ecological and morphological data to investigate the roles of geography, habitat use and lateral photophores in lanternfish speciation. Location: Global. Time period: Data collected between 1950 and 2015. Major taxa studied: Lanternfishes (Myctophidae). Methods: Ecological niche models (ENMs) were developed for 167 species, enabling the community composition of 33 mesopelagic ecoregions to be determined. Sequence data for seven protein‐coding regions from 175 species were used to reconstruct a phylogenetic tree of Myctophidae. Age‐overlap correlation tests were conducted using this phylogeny with outputs from ENMs (pairwise geographical overlap and pairwise ecological niche overlap, n = 136), in addition to matrices of pairwise depth overlap (n = 158) and photophore pattern dissimilarity (n = 161). Results: Communities assembled according to nine broad climatic regions, and recently diverged species pairs possessed greater geographical and ecological niche overlap than more distantly related species, indicating that sympatric or parapatric speciation might be dominant modes of divergence. Differences in photophore patterns increased with the relative age of speciation events, suggesting that photophore patterns are largely constrained by phylogeny. Main conclusions Based on this evidence, we suggest that large‐scale oceanographic features structure the diversity of lanternfish communities and that speciation within this family of deep‐water fishes might not have required geographical isolation. [ABSTRACT FROM AUTHOR]

Previous studies have found significant associations between estimated autozygosity - the proportion of an individual's genome contained in homozygous segments due to distant inbreeding - and multiple traits, including educational attainment (EA) and cognitive ability. In one study, estimated autozygosity showed a stronger association with parental EA than the subject's own EA. This was likely driven by parental EA's association with mobility: more educated parents tended to migrate further from their hometown, and because of the strong correlation between ancestry and geography in the Netherlands, these individuals chose partners farther from their ancestry and therefore more different from them genetically. We examined the associations between estimated autozygosity, cognitive ability, and parental EA in a contemporary sub-sample of adolescents from the Adolescent Brain Cognitive Development Study℠ (ABCD Study®) (analytic N = 6,504). We found a negative association between autozygosity and child cognitive ability consistent with previous studies, while the associations between autozygosity and parental EA were in the expected direction of effect (with greater levels of autozygosity being associated with lower EA) but the effect sizes were significantly weaker than those estimated in previous work. We also found a lower mean level of autozygosity in the ABCD sample compared to previous autozygosity studies, which may reflect overall decreasing levels of autozygosity over generations. Variation in spousal similarities in ancestral background in the ABCD study compared to other studies may explain the pattern of associations between estimated autozygosity, EA, and cognitive ability in the current study. [ABSTRACT FROM AUTHOR]

Premise: Reproductive fitness of individual plants depends on the timing of flowering, especially in mate‐limited populations, such as those in fragmented habitats. When flowering time traits are associated with differential reproductive success, the narrow‐sense heritability (h2) of traits will determine how rapidly trait means evolve in response to selection. Heritability of flowering time is documented in many annual plants. However, estimating h2 of flowering time in perennials presents additional methodological challenges, often including paternity assignment and trait expression over multiple years. Methods: We evaluated the h2 of onset and duration of flowering using offspring–midparent regressions and restricted maximum likelihood methods in an experimental population of an iterocarpic, perennial, herbaceous plant, Echinacea angustifolia, growing in natural conditions. We assessed the flowering time of the parental cohort in 2005 and 2006; the offspring in 2014 through 2017. We also examined the effects of the paternity assignment from Cervus and MasterBayes on estimates of h2. Results: We found substantial h2 for onset and duration of flowering. We also observed variation in estimates among years. The most reliable estimates for both traits fell in the range of 0.1–0.17. We found evidence of a genotype by year interaction for onset of flowering and strong evidence that genotypes are consistent in their duration of flowering across years. Conclusions: Substantial heritabilities in this population imply the capacity for a response to natural selection, while also suggesting the potential for differential contributions to adaptive evolution among seasons. [ABSTRACT FROM AUTHOR]

Individuals living in heterogeneous environments often choose microenvironments that provide benefits to their fitness. Theory predicts that such niche choice can promote rapid adaptation to novel environments and help maintain genetic diversity. An open question of large applied importance is how niche choice and niche choice evolution affect the evolution of insecticide resistance in phytophagous insects. We, therefore, developed an individual-based model based on phytophagous insects to examine the evolution of insecticide resistance and niche choice via oviposition preferences. To find biologically realistic parameter ranges, we performed an empirical literature survey on insecticide resistance in major agricultural pests and also conducted a density-dependent survival experiment using potato beetles. We find that, in comparison to a scenario where individuals randomly oviposit eggs on toxic or non-toxic plants, the evolution of niche choice generally leads to slower evolution of resistance and facilitates the coexistence of different phenotypes. Our simulations also reveal that recombination rate and dominance effects can influence the evolution of both niche choice and resistance. Thus, this study provides new insights into the effects of niche choice on resistance evolution and highlights the need for more studies on the genetic basis of resistance and choice., (© The Author(s) 2024. Published by Oxford University Press on behalf of the European Society of Evolutionary Biology.)

Theory predicts that performance-based habitat choice 1 , However, experimental evidence supporting these predictions has been largely lacking. In this study, we addressed this by inducing performance-based habitat choice in wild tree sparrows (Passer montanus) through the manipulation of differential access to transponder-operated feeders in two adjacent woodland areas. Sparrows overwhelmingly chose to move to and breed in the area where their feeding performance was highest, leading to local adaptation and increased reproductive success. Moreover, this non-random movement led to a high degree of assortative mating for transponder type and to reproductive isolation with respect to this ecological trait-all within a single generation. Our findings provide an empirical proof of principle that performance-based habitat choice can drive adaptive population divergence, even in the absence of divergent natural selection, underscoring its potential role as a key mechanism in ecological and evolutionary dynamics. This highlights the importance of integrating performance-based habitat choice into broader frameworks of adaptation and speciation, especially in the context of rapidly changing environments.2 , 3 -where individuals select environments based on their local performance-should be widespread in nature and significantly influence ecological and evolutionary processes, including local adaptation, population divergence, reproductive isolation, and speciation. 2 , 4 , 5 , 6 , 7 , 8 , 9 However, experimental evidence supporting these predictions has been largely lacking. In this study, we addressed this by inducing performance-based habitat choice in wild tree sparrows (Passer montanus) through the manipulation of differential access to transponder-operated feeders in two adjacent woodland areas. Sparrows overwhelmingly chose to move to and breed in the area where their feeding performance was highest, leading to local adaptation and increased reproductive success. Moreover, this non-random movement led to a high degree of assortative mating for transponder type and to reproductive isolation with respect to this ecological trait-all within a single generation. Our findings provide an empirical proof of principle that performance-based habitat choice can drive adaptive population divergence, even in the absence of divergent natural selection, underscoring its potential role as a key mechanism in ecological and evolutionary dynamics. This highlights the importance of integrating performance-based habitat choice into broader frameworks of adaptation and speciation, especially in the context of rapidly changing environments., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Secondary contact between incompletely isolated species can produce a wide variety of outcomes. The vinegar flies Drosophila simulans and D. sechellia diverged on islands in the Indian Ocean and are currently separated by partial pre- and postzygotic barriers. The recent discovery of hybridization between D. simulans and D. sechellia in the wild presents an opportunity to monitor the prevalence of alleles that influence hybridization between these sibling species. We therefore sought to identify those loci in females that affect interspecific mating, and we adapted a two-choice assay to capture female mate choice and female attractiveness simultaneously. We used shotgun sequencing to genotype female progeny of reciprocal F1 backcrosses at high resolution and performed QTL analysis. We found two major-effect QTL in both backcrosses, one on either arm of the third chromosome that each account for 32-37% of the difference in phenotype between species. The QTL of both backcrosses overlap and may each be alternate alleles of the same locus. Genotypes at these two loci followed an assortative mating pattern with D. simulans males but not D. sechellia males, which mated most frequently with females that were hybrid at both loci. These data reveal how different allele combinations at two major loci may promote isolation and hybridization in the same species pair. Identification of these QTL is an important step towards understanding how the genetic architecture of mate selection may shape the outcome of secondary contact., (© The Author(s) 2024. Published by Oxford University Press on behalf of The Genetics Society of America.)

Isolating barriers that drive speciation are commonly studied in the context of two-species hybrid zones. There is, however, evidence that more complex introgressive relationships are common in nature. Here, we use field observations and genomic analysis, including the sequencing and assembly of a novel reference genome, to study an emergent hybrid zone involving two colliding hybrid zones of three woodpecker species: red-breasted, red-naped, and yellow-bellied sapsuckers (Sphyrapicus ruber, S. nuchalis, and S. varius). Surveys of the area surrounding Prince George, British Columbia, Canada, show that all three species are sympatric, and Genotyping-by-Sequencing identifies hybrids from each species pair and birds with ancestry from all three species. Observations of phenotypes and genotypes of mated pairs provide evidence for assortative mating, though there is some heterospecific pairing. Hybridization is more extensive in this tri-species hybrid zone than in two di-species hybrid zones. However, there is no evidence of a hybrid swarm and admixture is constrained to contact zones, so we classify this region as a tension zone and invoke selection against hybrids as a likely mechanism maintaining species boundaries. Analysis of sapsucker age classes does not show disadvantages in hybrid survival to adulthood, so we speculate the selection upholding the tension zone may involve hybrid fecundity. Gene flow among all sapsuckers in di-species hybrid zones suggests introgression probably occurred before the formation of this tri-species hybrid zone, and might result from bridge hybridization, vagrancies, or other three-species interactions. [ABSTRACT FROM AUTHOR]

Advancing prior research that treated college graduates as a homogeneous group, we investigate heterogeneity in assortative mating patterns across baccalaureate degree fields. As baccalaureate degree fields are related to occupation, an important question remains about whether field-of-study homogamy begets occupational homogamy. We drew on the school-to-work transition literature, which shows that baccalaureate degree fields differ in their linkages to a targeted or diffuse set of occupational destinations. We analyzed 34,373 college-educated newlyweds from the 2009–2019 American Community Surveys. Log-linear analysis revealed a tendency for college graduates, especially those in vocational specific fields (fields that have targeted connections to specific occupations; e.g., law, health, and education), to marry a spouse in the same field. In addition, occupational homogamy was more likely to occur among couples with two spouses in the same vocational specific field than among couples with two spouses in different fields. By examining patterns and implications of field-of-study assortative mating, this study underlines the importance of horizontal stratification of higher education in shaping meeting opportunities and highlights how pathways from field of study to occupation structure marriage markets. [ABSTRACT FROM AUTHOR]

We investigated potential information content in red carotenoid-based undertail coverts of 28 pairs of breeding Great Spotted Woodpeckers by comparing plumage reflectance to measures of body condition and reproductive success. Plumage coloration was not significantly associated with sex or age, and did not correlate with body condition or the number of offspring fledged. Further, we found no evidence of assortative mating related to plumage colour. Our research provides an example of an exception from the commonly held hypothesis that carotenoid-based plumage coloration signals individual condition. Future surveys incorporating other plumage traits and physiological measures of condition in Great Spotted Woodpeckers are needed to verify our findings. [ABSTRACT FROM AUTHOR]

Simple Summary: The benefits of copulation with large males were investigated in the firebug, Pyrrhocoris apterus (L.) (Heteroptera). Sexually immature adults were transferred from the field and kept as female-male pairs with different partner size ratios. We investigated the influence of male body size on the number and weight of eggs and time elapsed from the transfer to their deposition. The expected positive effect of increasing male body size on the characteristics of female reproduction was not detected. Females and males of the abundant heteropteran species Pyrrhocoris apterus (L.) mate with the larger of the available partners. The male benefits from copulation with a large female, which is more productive than a small female. However, the benefit to females from copulation with a large male has not yet been investigated. Overwintered sexually immature adults were transferred from the field to indoors for a long day at 25 °C and subsequently kept as female-male pairs with different partner size ratios. The female lays eggs in several successive clutches. We investigated the influence of male size on the number and weight of eggs in individual clutches and the time elapsed from the transfer to their deposition. These characteristics of reproduction were first regressed on female size, and residuals of this regression were then regressed on male size. The positive effect of increasing male size on the characteristics of female reproduction manifested as a significant value of the latter regressions. The expected positive effect of increasing male body size on female reproductive characteristics was not detected. Several reasons for this deficiency are discussed. [ABSTRACT FROM AUTHOR]

Genetic data can provide insights into population history, but first, we must understand the patterns that complex histories leave in genomes. Here, we consider the admixed human population of Cabo Verde to understand the patterns of genetic variation left by social and demographic processes. First settled in the late 1400s, Cabo Verdeans are admixed descendants of Portuguese colonizers and enslaved West African people. We consider Cabo Verde's well-studied historical record alongside genome-wide SNP data from 563 individuals from 4 regions within the archipelago. We use genetic ancestry to test for patterns of nonrandom mating and sex-specific gene flow, and we examine the consequences of these processes for common demographic inference methods and genetic patterns. Notably, multiple population genetic tools that assume random mating underestimate the timing of admixture, but incorporating nonrandom mating produces estimates more consistent with historical records. We consider how admixture interrupts common summaries of genomic variation such as runs of homozygosity. While summaries of runs of homozygosity may be difficult to interpret in admixed populations, differentiating runs of homozygosity by length class shows that runs of homozygosity reflect historical differences between the islands in their contributions from the source populations and postadmixture population dynamics. Finally, we find higher African ancestry on the X chromosome than on the autosomes, consistent with an excess of European males and African females contributing to the gene pool. Considering these genomic insights into population history in the context of Cabo Verde's historical record, we can identify how assumptions in genetic models impact inference of population history more broadly. [ABSTRACT FROM AUTHOR]

Intermarriage among ethnic groups belonging to the same panethnic category (e.g., Asian, Latino) is an important indicator of the strength of panethnicity. Yet, most of the research on panethnic intermarriage uses older samples with signif­icant data limitations. In this article, I use data on recently married couples from the 2014–2018 American Community Surveys and the 1980 U.S. Census to analyze the likelihood of ethnic exogamy within the panethnic categories of Latino, East/Southeast Asian, and South Asian. I utilize a counterfactual marriage model that accounts for group size within local marriage markets, eliminates immigrants married abroad from analysis, and controls for birthplace and language endogamy. The results show that birthplace and language diversity are signif­icant barriers to ethnic exogamy among Asians but not Latinos. Once birthplace and language endogamy are held constant, panethnic intermarriage is far more likely among Asians than among Latinos. East/Southeast Asian ethnic exogamy has increased over time, while Latino ethnic exogamy has not. Furthermore, East/Southeast Asian and South Asian intermarriage remains rare, suggesting that panethnic intermarriage among Asians occurs within two separate melting pots. [ABSTRACT FROM AUTHOR]

Behavioral expression can vary both within‐ (i.e., plasticity) and among‐individuals (i.e., animal personality), and understanding the causes and consequences of variation at each of these levels is a major area of investigation in contemporary behavioral ecology. Here, we studied sources of variation in both plasticity and personality in nest defense behavior in Arctic peregrine falcons (Falco peregrinus tundrius) in two consecutive years. We found that peregrines adjusted their nest defense in response to nesting stage and year, revealing plastic, state‐dependent, adjustment of nest defense. At the same time, nest defense behavior was repeatable in peregrine falcons both within and between years. We tested if fluctuating selection on behavioral types (i.e., individuals average phenotypic expression) and/or assortative mating acted to maintain long‐term among‐individual differences in nest defense behavior. We found that selection on female nest defense differed across years; being positive in 1 year and negative in the other. We also found support for assortative mating in the first year, but disassortative mating in the second. We propose two potential explanations for the observed year‐specific patterns of nonrandom mating: (1) year‐specific plastic adjustment of nest defense and/or (2) changes in the age‐structure of the breeding population. These posthoc explanations are speculative, and require further study. Unfortunately, we could not evaluate this directly with the available data, and future studies are needed with more than 2 years of data on nest‐defense and fitness outcomes, and with a larger number of marked individuals, to properly evaluate these potential explanations. [ABSTRACT FROM AUTHOR]

It is thought that two species can coexist if they use different resources present in the environment, yet this assumes that species are completely reproductively isolated. We simulate coexistence outcomes for two sympatric species that are ecologically differentiated but have incomplete reproductive isolation. The consequences of interbreeding crucially depend on hybrid fitness. When hybrid fitness is high, just a small rate of hybridization can lead to collapse of two species into one. Low hybrid fitness can cause population declines, making extinction of one or both species likely. High intrinsic growth rates result in higher reproductive rates when populations are below carrying capacity, reducing the probability of extinction and increasing the probability of stable coexistence at moderate levels of assortative mating and hybrid fitness. Very strong but incomplete assortative mating can induce low hybrid fitness via a mating disadvantage to rare genotypes, and this can stabilize coexistence of two species at high but incomplete levels of assortative mating. Given these results and evidence that it may take many millions of years of divergence before related species become sympatric, we postulate that coexistence of closely related species is more often limited by insufficient assortative mating than by insufficient ecological differentiation. [ABSTRACT FROM AUTHOR]