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200 results for “assortativity”
Data from: Assortative mating frames establishment in a young island bird population
Successful island colonizations are key events to understand range dynamic processes, but studying a young population right after it reaches establishment is a rare opportunity in natural systems. However, the genetic structure of a recently established population may offer unique insights into its colonization history and demographic processes important for a successful colonization. Here, we studied the population genetics of a recently established island population of Eurasian blackbirds (Aves: Turdus merula) located on the island of Heligoland in the German North Sea. Using microsatellites, we genotyped the majority of the island population, including the nestlings, over a four-year period between 2004 and 2007. We also genotyped high numbers of migrants on stopover and mainland individuals, as they are potential founders of the island population. We identified two genetic clusters that comply with the migrating and mainland birds respectively. While most of the island birds belong to the mainland cluster, some breeding individuals and a low fraction of the offspring belong to the genetic cluster found in migrating individuals with almost no admixture between the two, pointing to assortative mating acting on the island population. We did not find any evidence for founder events and detected deviations from Hardy-Weinberg equilibrium that disappeared in cohorts of older age that coincide with a lower number of siblings in older cohorts. The observed genetic patterns unravel a complex colonization history to which migratory and mainland birds have contributed and which is characterized by assortative mating. Further research will be directed towards habitat selection and phenotypic differences as potential drivers of assortative mating in this island population.
Data from: Are assortative mating and genital divergence driven by reinforcement?
The evolution of assortative mating is a key part of the speciation process. Stronger assortment, or greater divergence in mating traits, between species pairs with overlapping ranges is commonly observed, but possible causes of this pattern of reproductive character displacement are difficult to distinguish. We use a multidisciplinary approach to provide a rare example where it is possible to distinguish among hypotheses concerning the evolution of reproductive character displacement. We build on an earlier comparative analysis that illustrated a strong pattern of greater divergence in penis form between pairs of sister species with overlapping ranges than between allopatric sister-species pairs, in a large clade of marine gastropods (Littorinidae). We investigate both assortative mating and divergence in male genitalia in one of the sister-species pairs, discriminating among three contrasting processes each of which can generate a pattern of reproductive character displacement: reinforcement, reproductive interference and the Templeton effect. We demonstrate reproductive character displacement in assortative mating, but not in genital form between this pair of sister species and use demographic models to distinguish among the different processes. Our results support a model with no gene flow since secondary contact and thus favour reproductive interference as the cause of reproductive character displacement for mate choice, rather than reinforcement. High gene flow within species argues against the Templeton effect. Secondary contact appears to have had little impact on genital divergence.
Data from: Assortative flocking in crossbills and implications for ecological speciation
How reproductive isolation is related to divergent natural selection is a central question in speciation. Here we focus on several ecologically specialised taxa or "call types" of red crossbills (Loxia curvirostra complex), one of the few groups of birds providing much evidence for ecological speciation. Call types differ in bill sizes and feeding capabilities, and also differ in vocalizations, such that contact calls provide information on crossbill phenotype. We found that two call types of red crossbills were more likely to approach playbacks of their own call type than those of heterotypics, and that their propensity to approach heterotypics decreased with increasing divergence in bill size. Although call similarity also decreased with increasing divergence in bill size, comparisons of responses to familiar versus unfamiliar call types indicate that the decrease in the propensity to approach heterotypics with increasing divergence in bill size was a learned response, and not a byproduct of calls diverging pleiotropically as bill size diverged. Because crossbills choose mates while in flocks, assortative flocking could lead indirectly to assortative mating as a byproduct. These patterns of association therefore provide a mechanism by which increasing divergent selection can lead to increasing reproductive isolation.
Data from: Female polyandry and size-assortative mating in isolated local populations of the Japanese common toad Bufo japonicus
In anurans, female polyandry under male harassment is distributed across taxa because of external aquatic fertilisation. According to the sexual selection theory, male–male competition for access to females is affected by the operational sex ratio (OSR) and population density. The Japanese common toad, Bufo japonicus, is widespread in mainland Japan, and like the European common toad, B. bufo, it engages in explosive breeding. We observed the breeding behaviour of B. japonicus in isolated local populations for three years in two breeding ponds with different population sizes and densities: large-low (L-pond) and small-high (S-pond). We analysed the relative polyandry ratio in egg clutches laid by females and estimated the size-assortative mating pattern to be an indicator of male–male competition in the two ponds. Both ponds tended to exhibit a size-assortative mating pattern; however, the frequency of polyandry was different in the two ponds (L-pond = 20% and S-pond = 90%). We also found that polyandry could occur without multiple amplexus with a high population density, i.e. eggs were often fertilised by free-swimming sperm in the small shallow pond. We propose that high female polyandry ratios without continuous male harassment are generated because of a male-biased OSR and a high population density in the small pond.
Data from: The scale-of-choice effect and how estimates of assortative mating in the wild can be biased due to heterogeneous samples
The mode in which sexual organisms choose mates is a key evolutionary process, as it can have a profound impact on fitness and speciation. One way to study mate choice in the wild is by measuring trait correlation between mates. Positive assortative mating is inferred when individuals of a mating pair display traits that are more similar than those expected under random mating while negative assortative mating is the opposite. A recent review of 1134 trait correlations found that positive estimates of assortative mating were more frequent and larger in magnitude than negative estimates. Here we describe the scale-of-choice effect (SCE), which occurs when mate choice exists at a smaller scale than that of the investigator's sampling, while simultaneously the trait is heterogeneously distributed at the true scale-of-choice. We demonstrate the SCE by Monte Carlo simulations and estimate it in two organisms showing positive (Littorina saxatilis) and negative (L. fabalis) assortative mating. Our results show that both positive and negative estimates are biased by the SCE by different magnitudes, typically towards positive values. Therefore, the low frequency of negative assortative mating observed in the literature may be due to the SCE's impact on correlation estimates, which demands new experimental evaluation.
Data from: Assortative mating by flowering time and its effect on correlated traits in variable environments
Reproductive timing is a key life history trait that impacts the pool of available mates, the environment experienced during flowering, and the expression of other traits through genetic covariation. Selection on phenology, and its consequences on other life history traits, has considerable implications in the context of ongoing climate change and shifting growing seasons. To test this, we grew field-collected seed from the wildflower Mimulus guttatus in a greenhouse to assess the standing genetic variation for flowering time and covariation with other traits. We then created full-sib families through phenological assortative mating and grew offspring in three photoperiod treatments representing seasonal variation in daylength. We find substantial quantitative genetic variation for the onset of flowering time, which covaried with vegetative traits. In the assortatively-mated offspring, we discover over 2-hours variation in critical photoperiod, so that families differed in the probability of flowering across treatments. Allocation to flowering and vegetative growth changed across the daylength treatments, with consistent direction and magnitude of covariation amongst flowering time and other traits. Our results suggest that future studies of flowering time evolution should consider the joint evolution of correlated traits and shifting seasonal selection to understand how environmental variation influences life histories.
Data from: Effects of assortative mate choice on the genomic and morphological structure of a hybrid zone between two bird subspecies
Phenotypic differentiation plays an important role in the formation and maintenance of reproductive barriers. In some cases, variation in a few key aspects of phenotype can promote and maintain divergence; hence the identification of these traits and their associations with patterns of genomic divergence are crucial for understanding the patterns and processes of population differentiation. We studied hybridization between the alba and personata subspecies of the white wagtail (Motacilla alba), and quantified divergence and introgression of multiple morphological traits and 19,437 SNP loci on a 3000 km transect. Our goal was to identify traits that may contribute to reproductive barriers and to assess how variation in these traits corresponds to patterns of genome-wide divergence. Variation in only one trait – head plumage patterning – was consistent with reproductive isolation. Transitions in head plumage were steep and occurred over otherwise morphologically and genetically homogeneous populations, whereas cline centers for other traits and genomic ancestry were displaced over one hundred kilometers from the head cline. Field observational data show that social pairs mated assortatively by head plumage, suggesting that these phenotypes are maintained by divergent mating preferences. In contrast, variation in all other traits and genetic markers could be explained by neutral diffusion, although weak ecological selection cannot be ruled out. Our results emphasize that assortative mating may maintain phenotypic differences independent of other processes shaping genome-wide variation, consistent with other recent findings that raise questions about the relative importance of mate choice, ecological selection and selectively neutral processes for divergent evolution.
Data from: Assortative mating and the maintenance of population structure in a natural hybrid zone
Understanding the factors that give rise to natural hybrid zones and govern their dynamics and structure is important to predicting the evolutionary consequences of hybridization. Here we use a combination of multi-generational population genetic data, mating patterns from a natural population, behavioral assays, and mark-recapture data within clinal hybrid zones of the genus Xiphophorus to test the role of assortative mating in maintaining population structure and the potential for ongoing genetic exchange between heterospecifics. Our data demonstrate that population structure is temporally robust and driven largely by assortative mating stemming from pre-copulatory isolation between pure species. Furthermore, mark-recapture data revealed that rates of migration within the same stream reach are far below the level needed to support population structure. Contrasting with many empirical studies of natural hybrid zones, there appeared to be no hybrid male dysfunction nor discrimination against hybrid males by pure parental females, and hybrid females mated and associated with pure species and hybrid males at random. Despite strong isolation between pure parentals, hybrids therefore can act as a conduit for genetic exchange between heterospecifics, which has been shown to increase the tempo of evolutionary change. Additionally, our findings highlight the complexity of natural hybrid zone dynamics, demonstrating that multivariate selection can give rise to patterns that do not fit classical models of hybrid zone evolution.
Data from: 'Prudent habitat choice': a novel mechanism of size-assortative mating
Assortative mating, an ubiquitous form of nonrandom mating, strongly impacts Darwinian fitness and can drive biological diversification. Despite its ecological and evolutionary importance, the behavioural processes underlying assortative mating are often unknown, and in particular, mechanisms not involving mate choice have been largely ignored so far. Here, we propose that assortative mating can arise from 'prudent habitat choice', a general mechanism that acts under natural selection, and that it can occur despite a complete mixing of phenotypes. We show that in the cichlid Eretmodus cyanostictus size-assortative mating ensues, because individuals of weaker competitive ability ignore high-quality but strongly competed habitat patches. Previous studies showed that in E. cyanostictus, size-based mate preferences are absent. By field and laboratory experiments, here we showed that (i) habitat quality and body size are correlated in this species; (ii) territories with more stone cover are preferred by both sexes in the absence of competition; and (iii) smaller fish prudently occupy vacant territories of worse quality than do larger fish. Prudent habitat choice is likely to be a widespread mechanism of assortative mating, as both preferences for and dominance-based access to high-quality habitats are generic phenomena in animals.
Cooperation in public goods game does not require assortment and depends on population density
<p>The threshold public goods game is one of the best-known models of nonlinear public goods dilemmas. Cooperators and defectors typically coexist in this game when the population is assumed to follow the so-called structured deme model. In this paper we develop a dynamical model of a general N-player game in which there is no deme structure: individuals interact with randomly chosen neighbours and selection occurs between randomly chosen pairs of indi- viduals. We show that in the deterministic limit the dynamics in this model leads to the same replicator dynamics as in the structured deme model, i.e. coexistence of cooperators and defectors is typical in threshold public goods game even when the population is completely well-mixed. We extend the model to study the effect of density dependence and density fluctuation on the dynamics. We show analytically and numerically that decreasing population density increases the equilibrium frequency of cooperators till the fixation of this strategy, but below a critical density coop- erators abruptly disappear from the population. Our numerical investigations show that weak density fluctuations enhance cooperation, while strong fluctuations suppress it.</p>
Phenotypic assortment by morphology in social partners of the forked fungus beetle Bolitotherus cornutus
<p>Social interactions with conspecifics can dramatically affect an individual's fitness. The positive or negative consequences of interacting with social partners typically depend on the value of traits that they express. These pathways of social selection connect the traits and genes expressed in some individuals to the fitness realized by others, thereby altering the total phenotypic selection on and evolutionary response of traits across the multivariate phenotype. The downstream effects of social selection are mediated by the patterns of phenotypic assortment between focal individuals and their social partners (the interactant covariance, C<sup>ij</sup> , or the multivariate form, C<sup>I</sup>). Depending on the sign and magnitude of the interactant covariance, the direction of social selection can be reinforced, reversed, or erased. We report estimates of C<sup>ij </sup>from a variety of studies of forked fungus beetles to address the largely unexplored questions of consistency and plasticity of phenotypic assortment in natural populations. We found that phenotypic assortment of male beetles based on body size or horn length was highly variable among subpopulations, but that those differences also were broadly consistent from year to year. At the same time, the strength and direction of C<sup>ij </sup>changed quickly in response to experimental changes in resource distribution and social properties of populations. Generally, interactant covariances were more negative in contexts in which the number of social interactions was greater in both field and experimental situations. These results suggest that patterns of phenotypic assortment could be important contributors to variability in multilevel selection through their mediation of social selection gradients.</p>
Replication data for: Processed food intake assortativity in the personal networks of older adults
<p>This is the replication data for the scientific paper titled "Processed food intake assortativity in the personal networks of older adults." For details on how to use the data files, please consider the "Supplementary Material" file and the paper preprint where the context of the study and the variables of interest are presented.</p>
Data from: Linking intra- and interspecific assortative mating: consequences for asymmetric sexual isolation
Assortative mating is of interest because of its role in speciation and the maintenance of species boundaries. However, we know little about how within-species assortment is related to interspecific sexual isolation. Most previous studies of assortative mating have focused on a single trait in males and females, rather than utilizing multivariate trait information. Here we investigate how intraspecific assortative mating relates to sexual isolation in two sympatric and congeneric damselfly species (genus Calopteryx). We connect intraspecific assortment to interspecific sexual isolation by combining field observations, mate preference experiments and enforced copulation experiments. Using canonical correlation analysis, we demonstrate multivariate intraspecific assortment for body size and body shape. Males of the smaller species mate more frequently with heterospecific females than males of the larger species, which showed less attraction to small heterospecific females. Field experiments suggest that sexual isolation asymmetry is caused by male preferences for large heterospecific females, rather than by mechanical isolation due to interspecific size differences or female preferences for large males. Male preferences for large females and male-male competition for high quality females can therefore counteract sexual isolation. This sexual isolation asymmetry therefore indicates that sexual selection currently opposes a species boundary.
Mutual mate choice and assortative mating in relation to a carotenoid-based color trait in blue tits
<p>Choosing an appropriate partner is a critical decision for many animal species. However, many mechanisms involved in mate choice are still poorly understood. Do both males and females choose their sexual partners, do both sexes use the same criteria for choosing, and do their own phenotype influence the choices they make, are questions that need further investigation. Over two successive experiments conducted in captivity with hand-reared blue tits (Cyanistes caeruleus), we manipulated the color of the chest plumage, a secondary sexual trait that reflects an individual's condition, to create two different color morphs (one pale and one colored). We then tested whether both sexes express a preference, whether they are attracted to the same morphs, and if the subjects' own chest color influences the preference they show. Our data reveal that both sexes are choosy, with females tending to be slightly choosier than males. We also show that both sexes preferentially select individuals with a pale chest plumage over colorful individuals, and this was again more pronounced in females. Finally, paler individuals tend to be selected by birds that are themselves pale, even if this phenotype matching was not very robust. Such a preference for paler individuals is intriguing since mates are predicted to associate with individuals displaying higher, not lower, value of quality signals. It could result from adaptive mechanisms related to avoidance of aggressiveness in confined environment, avoidance of conflicting sexual signals within individuals, or from cultural mechanisms leading to preference for individuals that match its own phenotype.</p>
Assorted x1d and c1d test files
<p>Assorted x1d and c1d test files</p>
Data from: Spatiotemporal segregation by migratory phenotype indicates potential for assortative mating in lake sturgeon
<p>Migratory diversity can promote population differentiation if sympatric phenotypes become temporally, spatially, or behaviorally segregated during breeding. In this study, the potential for spatiotemporal segregation was tested among three migratory phenotypes of lake sturgeon (<em>Acipenser fulvescens</em>) that spawn in the St. Clair River of North America's Laurentian Great Lakes but differ in how often they migrate into the river and in which direction they move after spawning. Acoustic telemetry over nine years monitored use of two major spawning sites by lake sturgeon that moved north to overwinter in Lake Huron or south to overwinter in Lake St. Clair. Lake St. Clair migrants were further distinguished by whether they migrated into the St. Clair River each year (annual migrants) or intermittently (intermittent migrants). Social network analyses indicated lake sturgeon generally co-occurred with individuals of the same migratory phenotype more often than with different migratory phenotypes. A direct test for differences in space use revealed one site was almost exclusively visited by Lake St. Clair migrants whereas the other site was visited by Lake Huron migrants, intermittent Lake St. Clair migrants, and, to a lesser extent, annual Lake St. Clair migrants. Analysis of arrival and departure dates indicated an opportunity for co-occurrence at the site visited by all phenotypes but showed Lake Huron migrants arrived approximately two weeks before Lake St. Clair migrants. Taken together, our results indicated partial spatiotemporal segregation of migratory phenotypes that may generate assortative mating and promote population differentiation.</p>
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Data from: Extensive seed and pollen dispersal and assortative mating in the rain forest tree Entandrophragma cylindricum (Meliaceae) inferred from indirect and direct analyses
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Data from: No assortative mating based on size in black guillemots breeding in the Canadian Arctic
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Data from: Can MHC-assortative partner choice promote offspring diversity? A new combination of MHC-dependent behaviors among sexes in a highly successful invasive mammal
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