scholarly journals Assortative mating can impede or facilitate fixation of underdominant alleles

2016 ◽  
Author(s):  
Mitchell G Newberry ◽  
David M McCandlish ◽  
Joshua B Plotkin
Keyword(s):  
Sexual Selection ◽  
Assortative Mating ◽  
Mechanistic Model ◽  
Random Mating ◽  
Complex Form ◽  
Rare Alleles ◽  
Large Populations ◽  
Classical Models ◽  
Mating Opportunities ◽  
Coloration Patterns

ABSTRACTAlthough underdominant mutations have undoubtedly fixed between divergent species, classical models of population genetics suggest underdominant alleles should be purged quickly, except in small or subdivided populations. Here we study the fixation of underdominant alleles at loci that also influence mate choice, such as loci encoding coloration patterns visible to mates and predators alike. We analyze a mechanistic model of positive assortative mating in which individuals havenchances to sample compatible mates. This one-parameter model naturally spans the two classical extremes of random mating (n= 1) and complete assortment (n→ ∞), and yet it produces a complex form of sexual selection that depends non-monotonically on the number of mating opportunities,n. The resulting interaction between viability selection and sexual selection can either inhibit or facilitate fixation of underdominant alleles, compared to random mating. As the number of mating opportunities increases, underdominant alleles can fix at rates that even approach the neutral substitution rate. This result is counterintuitive because sexual selection and underdominance each suppress rare alleles in this model, and yet in combination they can promote the fixation of rare alleles. This phenomenon constitutes a new mechanism for the fixation of underdominant alleles in large populations, and it illustrates how incorporating life history characteristics can alter the predictions of population-genetic models for evolutionary change.

Size and shape assortative mating in Japanese beetles (Popillia japonica)

2020 ◽  
Vol 98 (10) ◽  
pp. 691-695
Author(s):  
Clint D. Kelly
Keyword(s):  
Sexual Selection ◽  
Assortative Mating ◽  
Insect Pest ◽  
Popillia Japonica ◽  
Japanese Beetle ◽  
Size And Shape ◽  
Temporal Autocorrelation ◽  
Mating Opportunities ◽  
Body Shapes ◽  
Similar Body

Assortative mating is hypothesized to be a product of sexual selection, mating constraints, or temporal autocorrelation. I test these hypotheses in the Japanese beetle (Popillia japonica Newman, 1841), a sexually size dimorphic invasive insect pest in North America, by measuring the size and shape of bodies and wings of pair members in a wild population. Because male P. japonica prefer to mate with larger females and larger males outcompete rivals for mating opportunities, sexual selection is expected to produce size-related assortative mating. The current study did not support this hypothesis. The mating constraints hypothesis was also not supported because beetle pairs did not have similar body shapes. I, however, did find support for the temporal autocorrelation hypothesis as the wing size and shape of pair members were significantly correlated. This mating pattern likely arises due to individuals with larger and more slender wings arriving earlier at aggregation sites and pairing according to their arrival sequence. Although I found less support for the sexual selection hypothesis, I argue that mate choice might play an important, but secondary, role to temporal autocorrelation in explaining assortative mating in Japanese beetles.

scholarly journals Patterns of introgression vary within an avian hybrid zone

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Logan M. Maxwell ◽  
Jennifer Walsh ◽  
Brian J. Olsen ◽  
Adrienne I. Kovach
Keyword(s):  
Sexual Selection ◽  
Assortative Mating ◽  
Hybrid Zone ◽  
Spatial Scales ◽  
Random Mating ◽  
Relative Influence ◽  
Hybrid Index ◽  
Interspecific Mating ◽  
Selective Pressures ◽  
Demographic Processes

Abstract Background Exploring hybrid zone dynamics at different spatial scales allows for better understanding of local factors that influence hybrid zone structure. In this study, we tested hypotheses about drivers of introgression at two spatial scales within the Saltmarsh Sparrow (Ammospiza caudacuta) and Nelson’s Sparrow (A. nelsoni) hybrid zone. Specifically, we evaluated the influence of neutral demographic processes (relative species abundance), natural selection (exogenous environmental factors and genetic incompatibilities), and sexual selection (assortative mating) in this mosaic hybrid zone. By intensively sampling adults (n = 218) and chicks (n = 326) at two geographically proximate locations in the center of the hybrid zone, we determined patterns of introgression on a fine scale across sites of differing habitat. We made broadscale comparisons of patterns from the center with those of prior studies in the southern edge of the hybrid zone. Results A panel of fixed SNPs (135) identified from ddRAD sequencing was used to calculate a hybrid index and determine genotypic composition/admixture level of the populations. Another panel of polymorphic SNPs (589) was used to assign paternity and reconstruct mating pairs to test for sexual selection. On a broad-scale, patterns of introgression were not explained by random mating within marshes. We found high rates of back-crossing and similarly low rates of recent-generation (F1/F2) hybrids in the center and south of the zone. Offspring genotypic proportions did not meet those expected from random mating within the parental genotypic distribution. Additionally, we observed half as many F1/F2 hybrid female adults than nestlings, while respective male groups showed no difference, in support of Haldane’s Rule. The observed proportion of interspecific mating was lower than expected when accounting for mate availability, indicating assortative mating was limiting widespread hybridization. On a fine spatial scale, we found variation in the relative influence of neutral and selective forces between inland and coastal habitats, with the smaller, inland marsh influenced primarily by neutral demographic processes, and the expansive, coastal marsh experiencing higher selective pressures in the form of natural (exogenous and endogenous) and sexual selection. Conclusions Multiple drivers of introgression, including neutral and selective pressures (exogenous, endogenous, and sexual selection), are structuring this hybrid zone, and their relative influence is site and context-dependent.

scholarly journals Multi-model inference of non-random mating from an information theoretic approach

2018 ◽  
Author(s):  
Antonio Carvajal-Rodriguez
Keyword(s):  
Sexual Selection ◽  
Model Selection ◽  
Mate Choice ◽  
Assortative Mating ◽  
Random Mating ◽  
Intrasexual Competition ◽  
Maximum Likelihood Estimates ◽  
Theoretic Approach ◽  
Multimodel Inference ◽  
Discrete Traits

AbstractNon-random mating has a significant impact on the evolution of organisms. Here, I developed a modelling framework for discrete traits (with any number of phenotypes) to explore different models connecting the non-random mating causes (intra sexual competition and/or mate choice) and their consequences (sexual selection and/or assortative mating).I derived the formulas for the maximum likelihood estimates of each model and used information criteria for performing multimodel inference. Simulation results showed a good performance of both model selection and parameter estimation. The methodology was applied to data from Galician Littorina saxatilis ecotypes, to show that the mating pattern is better described by models with two parameters that involve both mate choice and intrasexual competition, generating positive assortative mating plus female sexual selection.As far as I know, this is the first standardized methodology for model selection and multimodel inference of mating parameters for discrete traits. The advantages of this framework include the ability of setting up models from which the parameters connect causes, as intrasexual competition and mate choice, with their outcome in the form of data patterns of sexual selection and assortative mating. For some models, the parameters may have a double effect i.e. they cause both kind of patterns, while for others models there are separated parameters for one kind of pattern or another.The full methodology was implemented in a software called InfoMating (available at http://acraaj.webs6.uvigo.es/InfoMating/Infomating.htm).

scholarly journals Assortative mating by population of origin in a mechanistic model of admixture

2019 ◽  
Author(s):  
Amy Goldberg ◽  
Ananya Rastogi ◽  
Noah A Rosenberg
Keyword(s):  
Assortative Mating ◽  
Mechanistic Model ◽  
Random Mating ◽  
Population History ◽  
Source Population ◽  
Mating Preferences ◽  
Positive Assortative Mating ◽  
Special Cases ◽  
Mating Population ◽  
Over Time

AbstractPopulations whose mating pairs have levels of similarity in phenotypes or genotypes that differ systematically from the level expected under random mating are described as experiencing assortative mating. Excess similarity in mating pairs is termed positive assortative mating, and excess dissimilarity is negative assortative mating. In humans, empirical studies suggest that mating pairs from various admixed populations—whose ancestry derives from two or more source populations—possess correlated ancestry components that indicate the occurrence of positive assortative mating on the basis of ancestry. Generalizing a two-sex mechanistic admixture model, we devise a model of one form of ancestry-assortative mating that occurs through preferential mating based on source population. Under the model, we study the moments of the admixture fraction distribution for different assumptions about mating preferences, including both positive and negative assortative mating by population. We consider the special cases of assortative mating by population that involve a single admixture event and that consider a model of constant contributions to the admixed population over time. We demonstrate that whereas the mean admixture under assortative mating is equivalent to that of a corresponding randomly mating population, the variance of admixture depends on the level and direction of assortative mating. In contrast to standard settings in which positive assortment increases variation within a population, certain assortative mating scenarios allow the variance of admixture to decrease relative to a corresponding randomly mating population: with the three populations we consider, the variance-increasing effect of positive assortative mating within a population might be overwhelmed by a variance-decreasing effect emerging from mating preferences involving other pairs of populations. The effect of assortative mating is smaller on the X chromosome than the autosomes because inheritance of the X in males depends only on the mother’s ancestry, not on the mating pair. Because the variance of admixture is informative about the timing of admixture and possibly about sex-biased admixture contributions, the effects of assortative mating are important to consider in inferring features of population history from distributions of admixture values. Our model provides a framework to quantitatively study assortative mating under flexible scenarios of admixture over time.

Assortative mating in a fiddler crab

Behaviour ◽  
2016 ◽  
Vol 153 (2) ◽  
pp. 175-185 ◽  
Author(s):  
H.L. Clark ◽  
P.R.Y. Backwell
Keyword(s):  
Sexual Selection ◽  
Assortative Mating ◽  
Fiddler Crab ◽  
Size Range ◽  
Random Mating ◽  
Mate Availability ◽  
Mating Period ◽  
Full Size ◽  
Mechanical Constraints ◽  
Evolutionary Consequences

Non-random mating, particularly positive size-assortative mating, is common and can have major evolutionary consequences. The causes of size-assortative mating, however, are rarely examined. Here we explore the possibility of sexual selection, mate availability and mating constraints causing the strong correlation between male and female sizes in the fiddler crabUca mjoebergi. We show that the full size range of males is available to females throughout the mating period, so mate availability is unlikely to cause size-assortative mating in this species. We also show that mechanical constraints do not prevent females from entering the burrows or mating with the full size range of males. We suggest that the strong size assortative mating that we observed throughout the mating cycle is driven by sexual selection. Both males and females prefer large partners. The benefit to mating with large partners needs further investigation.

scholarly journals Quantifying the prevalence of assortative mating in a human population

2019 ◽  
Author(s):  
Klaus Jaffe
Keyword(s):  
Assortative Mating ◽  
Genetic Relatedness ◽  
Random Mating ◽  
Human Populations ◽  
Genetic Composition ◽  
Genetic Studies ◽  
Maintenance Of Sex ◽  
Animal Populations ◽  
The Uk ◽  
First Time

AbstractFor the first time, empirical evidence allowed to construct the frequency distribution of a genetic relatedness index between the parents of about half a million individuals living in the UK. The results suggest that over 30% of the population is the product of parents mating assortatively. The rest is probably the offspring of parents matching the genetic composition of their partners randomly. High degrees of genetic relatedness between parents, i.e. extreme inbreeding, was rare. This result shows that assortative mating is likely to be highly prevalent in human populations. Thus, assuming only random mating among humans, as widely done in ecology and population genetic studies, is not an appropriate approximation to reality. The existence of assortative mating has to be accounted for. The results suggest the conclusion that both, assortative and random mating, are evolutionary stable strategies. This improved insight allows to better understand complex evolutionary phenomena, such as the emergence and maintenance of sex, the speed of adaptation, runaway adaptation, maintenance of cooperation, and many others in human and animal populations.

scholarly journals EFFECTS OF POPULATION SIZE AND SELECTION INTENSITY ON RESPONSES TO DISRUPTIVE SELECTION IN DROSOPHILA MELANOGASTER

Genetics ◽  
1974 ◽  
Vol 78 (2) ◽  
pp. 715-735
Author(s):  
J S F Barker ◽  
L J E Karlsson
Keyword(s):  
Assortative Mating ◽  
Random Mating ◽  
Female Parent ◽  
Disruptive Selection ◽  
Lethal Gene ◽  
Selection Intensity ◽  
Bristle Number ◽  
Isolation Index ◽  
Selection Intensities ◽  
High Selection

ABSTRACT Disruptive selection for sternopleural bristle number with opportunity for random mating was done in the four treatment combinations of two population sizes (40 pairs and 8 pairs of selected parents) and two selection intensities (1 in 40 and 1 in 2). In each generation, matings among selected parents were observed in a mating chamber, and progeny collected separately from each female parent. In the high number, high selection intensity treatment, divergence between the high and low parts ceased about generation 11. The isolation index increased rapidly to generation 3, but then fluctuated to termination of the population at generation 17. The overall isolation index was significant, indicating a real tendency to assortative mating. The failure of the isolation index to increase after generation 3 was attributed to lower average mating fitness of high males (due to inbreeding) and reduced receptivity of low females (due to a homozygous lethal gene with a large effect on sternopleural bristle number in heterozygotes). In the two low number treatments, isolation indices fluctuated from generation to generation with no obvious trends, and none of the overall isolation indices were significantly different from zero. The high number, low selection intensity treatment showed very little divergence, and one of the replicates showed, in contrast with expectation and the high number, high selection intensity treatment, a significant tendency to disassortative mating. Intense disruptive selection may lead to assortative mating.

scholarly journals The effect of sexual selection on adaptation and extinction under increasing temperatures

2018 ◽  
Vol 285 (1877) ◽  
pp. 20180303 ◽  
Author(s):  
Jonathan M. Parrett ◽  
Robert J. Knell
Keyword(s):  
Sexual Selection ◽  
Environmental Changes ◽  
Population Level ◽  
Offspring Survival ◽  
Positive Effects ◽  
Fitness Consequences ◽  
Indian Meal ◽  
Mating Opportunities ◽  
Entire Experiment ◽  
Positive Effect

Strong sexual selection has been reported to both enhance and hinder the adaptive capacity and persistence of populations when exposed to novel environments. Consequently, how sexual selection influences population adaption and persistence under stress remains widely debated. Here, we present two empirical investigations of the fitness consequences of sexual selection on populations of the Indian meal moth, Plodia interpunctella, exposed to stable or gradually increasing temperatures. When faced with increasing temperatures, strong sexual selection was associated with both increased fecundity and offspring survival compared with populations experiencing weak sexual selection, suggesting sexual selection acts to drive adaptive evolution by favouring beneficial alleles. Strong sexual selection did not, however, delay extinction when the temperature became excessively high. By manipulating individuals' mating opportunities during fitness assays, we were able to assess the effect of multiple mating independently from the effect of population-level sexual selection, and found that polyandry has a positive effect on both fecundity and offspring survival under increasing temperatures in those populations evolving with weak sexual selection. Within stable temperatures, there were some benefits from strong sexual selection but these were not consistent across the entire experiment, possibly reflecting changing costs and benefits of sexual selection under stabilizing and directional selection. These results indicate that sexual selection can provide a buffer against climate change and increase adaptation rates within a continuously changing environment. These positive effects of sexual selection may, however, be too small to protect populations and delay extinction when environmental changes are relatively rapid.

Non-random mating and sexual selection

1985 ◽  
pp. 383-398
Author(s):  
Bryan F. J. Manly
Keyword(s):  
Sexual Selection ◽  
Random Mating
Sign in / Sign up

Export Citation Format

Share Document