Sexual difference in modes of selection on the pleopods of crayfish (Decapoda: Astacoidea) revealed by the allometry of developmentally homologous traits

2003 ◽  
Vol 81 (6) ◽  
pp. 971-978 ◽  
Author(s):  
Naoko Kato ◽  
Tadashi Miyashita
Keyword(s):  
Sexual Difference ◽  
Procambarus Clarkii ◽  
Regression Line ◽  
Directional Selection ◽  
Stabilizing Selection ◽  
Allometric Relationships ◽  
Selective Force ◽  
Developmental Constraints ◽  
Selection Pressures ◽  
Males And Females

Crayfish have five pairs of abdominal limbs called pleopods. In males, the first and second pairs of pleopods are used for transferring spermatophores to the female during copulation. The remaining pleopods in males have no obvious function. Female crayfish use their pleopods to carry eggs. Accordingly, it is expected that the selection pressures that act on the pleopods differ between males and females. To test this hypothesis, we estimated modes of selection on pleopods in two species of crayfish (Procambarus clarkii and Pacifastacus trowbridgii) by comparing allometric relationships in functional and nonfunctional pleopods. Since pleopods are serially homologous traits, developmental constraints on these traits appear to be minimal. The lengths of the first male pleopods, used in copulation, showed lower allometric values and less dispersion around the regression line, suggesting that they have been under stabilizing selection. This likely occurs because the major selective force is the ability of males to copulate with females of various sizes. The pleopods of females showed higher allometric values than pleopods of males without an assigned function. This suggests that the pleopods of females have been under directional selection, most likely because they are longer and can therefore carry more eggs.

scholarly journals How development affects evolution

2021 ◽  
Author(s):  
Mauricio González-Forero ◽  
Andy Gardner
Keyword(s):  
Niche Construction ◽  
Fitness Landscape ◽  
Stabilizing Selection ◽  
Mathematical Framework ◽  
Phenotypic Evolution ◽  
Landscape Development ◽  
Developmental Constraints ◽  
Evolutionary Pathway ◽  
Punctuated Equilibria ◽  
Adaptive Radiations

How development affects evolution. A mathematical framework that explicitly integrates development into evolution has recently been derived. Here we use this framework to analyse how development affects evolution. We show that, whilst selection pushes genetic and phenotypic evolution uphill on the fitness landscape, development determines the admissible evolutionary pathway, such that evolutionary outcomes occur at path peaks, which need not be peaks of the fitness landscape. Development can generate path peaks, triggering adaptive radiations, even on constant, single-peak landscapes. Phenotypic plasticity, niche construction, extra-genetic inheritance, and developmental bias variously alter the evolutionary path and hence the outcome. Selective development, whereby phenotype construction may point in the adaptive direction, may induce evolution either towards or away landscape peaks depending on the developmental constraints. Additionally, developmental propagation of phenotypic effects over age allows for the evolution of negative senescence. These results help explain empirical observations including punctuated equilibria, the paradox of stasis, the rarity of stabilizing selection, and negative senescence, and show that development has a major role in evolution.

scholarly journals Quantitative genetic variability maintained by mutation-stabilizing selection balance: sampling variation and response to subsequent directional selection

1989 ◽  
Vol 54 (1) ◽  
pp. 45-58 ◽  
Author(s):  
Peter D. Keightley ◽  
William G. Hill
Keyword(s):  
Genetic Variance ◽  
Directional Selection ◽  
Quantitative Character ◽  
Stabilizing Selection ◽  
Effective Population ◽  
Selection Responses ◽  
Quantitative Genetic ◽  
Before And After ◽  
Cage Population ◽  
Selection Of

SummaryA model of genetic variation of a quantitative character subject to the simultaneous effects of mutation, selection and drift is investigated. Predictions are obtained for the variance of the genetic variance among independent lines at equilibrium with stabilizing selection. These indicate that the coefficient of variation of the genetic variance among lines is relatively insensitive to the strength of stabilizing selection on the character. The effects on the genetic variance of a change of mode of selection from stabilizing to directional selection are investigated. This is intended to model directional selection of a character in a sample of individuals from a natural or long-established cage population. The pattern of change of variance from directional selection is strongly influenced by the strengths of selection at individual loci in relation to effective population size before and after the change of regime. Patterns of change of variance and selection responses from Monte Carlo simulation are compared to selection responses observed in experiments. These indicate that changes in variance with directional selection are not very different from those due to drift alone in the experiments, and do not necessarily give information on the presence of stabilizing selection or its strength.

scholarly journals Sex-Specific Selection Drives the Evolution of Alternative Splicing in Birds

2020 ◽  
Author(s):  
Thea F Rogers ◽  
Daniela H Palmer ◽  
Alison E Wright
Keyword(s):  
Gene Expression ◽  
Sex Differences ◽  
Alternative Splicing ◽  
Bird Species ◽  
Gene Expression Level ◽  
Expression Level ◽  
Selection Pressures ◽  
Specific Adaptation ◽  
Beneficial Effects ◽  
Males And Females

Abstract Males and females of the same species share the majority of their genomes, yet they are frequently exposed to conflicting selection pressures. Gene regulation is widely assumed to resolve these conflicting sex-specific selection pressures, and although there has been considerable focus on elucidating the role of gene expression level in sex-specific adaptation, other regulatory mechanisms have been overlooked. Alternative splicing enables different transcripts to be generated from the same gene, meaning that exons which have sex-specific beneficial effects can in theory be retained in the gene product, whereas exons with detrimental effects can be skipped. However, at present, little is known about how sex-specific selection acts on broad patterns of alternative splicing. Here, we investigate alternative splicing across males and females of multiple bird species. We identify hundreds of genes that have sex-specific patterns of splicing and establish that sex differences in splicing are correlated with phenotypic sex differences. Additionally, we find that alternatively spliced genes have evolved rapidly as a result of sex-specific selection and suggest that sex differences in splicing offer another route to sex-specific adaptation when gene expression level changes are limited by functional constraints. Overall, our results shed light on how a diverse transcriptional framework can give rise to the evolution of phenotypic sexual dimorphism.

The Pop Culture of Sex: An Evolutionary Window on the Worlds of Pornography and Romance

2012 ◽  
Vol 16 (2) ◽  
pp. 152-160 ◽  
Author(s):  
Catherine Salmon
Keyword(s):  
Evolutionary History ◽  
Human Sexuality ◽  
Pop Culture ◽  
Modern Technology ◽  
Selection Pressures ◽  
Male And Female ◽  
Widespread Distribution ◽  
The World ◽  
Males And Females ◽  
The Way

Pornography and romance, at first glance they seem to be two genres that are almost polar opposites. Yet both are the products of our evolved human sexuality and both have been the subjects of a variety of authors and researchers. Particularly in the case of pornography, some have argued strongly against its very existence, charging it, its creators and consumers with many of the evils in the world (real and imagined). In the case of romance, many have been derogatory and dismissive of the writers' skills and the readers' minds. In this article, I hope to introduce a different approach to these genres, through an evolutionary lens that serves to illuminate the way in which our sexual natures combined with modern technology to create such widespread distribution and sales. Romance and pornography are both multibillion dollar industries, and their stark contrasts reflect the deep divide at the heart of male and female erotic fantasies. These differences reflect the fact that the selection pressures males and females faced in the reproductive realm over human evolutionary history were not identical.

scholarly journals The relative impact of evolving pleiotropy and mutational correlation on trait divergence

2019 ◽  
Author(s):  
Jobran Chebib ◽  
Frédéric Guillaume
Keyword(s):  
Stochastic Model ◽  
Directional Selection ◽  
Population Variation ◽  
The Other ◽  
Common Mechanism ◽  
Stabilizing Selection ◽  
Relative Impact ◽  
Relative Importance ◽  
Trait Evolution ◽  
Trait Divergence

AbstractBoth pleiotropic connectivity and mutational correlations can restrict the divergence of traits under directional selection, but it is unknown which is more important in trait evolution. In order to address this question, we create a model that permits within-population variation in both pleiotropic connectivity and mutational correlation, and compare their relative importance to trait evolution. Specifically, we developed an individual-based, stochastic model where mutations can affect whether a locus affects a trait and the extent of mutational correlations in a population. We find that traits can diverge whether there is evolution in pleiotropic connectivity or mutational correlation but when both can evolve then evolution in pleiotropic connectivity is more likely to allow for divergence to occur. The most common genotype found in this case is characterized by having one locus that maintains connectivity to all traits and another that loses connectivity to the traits under stabilizing selection (subfunctionalization). This genotype is favoured because it allows the subfunctionalized locus to accumulate greater effect size alleles, contributing to increasingly divergent trait values in the traits under directional selection without changing the trait values of the other traits (genetic modularization). These results provide evidence that partial subfunctionalization of pleiotropic loci may be a common mechanism of trait divergence under regimes of corridor selection.

scholarly journals The quantitative genetic consequences of pleiotropy under stabilizing and directional selection.

Genetics ◽  
1990 ◽  
Vol 125 (1) ◽  
pp. 207-213 ◽  
Author(s):  
M Slatkin ◽  
S A Frank
Keyword(s):  
Directional Selection ◽  
Stabilizing Selection ◽  
Normal Model ◽  
Multivariate Normal ◽  
Genetic Covariance ◽  
Phenotypic Characters ◽  
House Of Cards ◽  
Quantitative Genetic ◽  
Stepwise Mutation ◽  
Multivariate Normal Model

Abstract The independence of two phenotypic characters affected by both pleiotropic and nonpleiotropic mutations is investigated using a generalization of M. Slatkin's stepwise mutation model of 1987. The model is used to determine whether predictions of either the multivariate normal model introduced in 1980 by R. Lande or the house-of-cards model introduced in 1985 by M. Turelli can be regarded as typical of models that are intermediate between them. We found that, under stabilizing selection, the variance of one character at equilibrium may depend on the strength of stabilizing selection on the other character (as in the house-of-cards model) or not (as in the multivariate normal model) depending on the types of mutations that can occur. Similarly, under directional selection, the genetic covariance between two characters may increase substantially (as in the house-of-cards model) or not (as in the multivariate normal model) depending on the kinds of mutations that are assumed to occur. Hence, even for the simple model we consider, neither the house-of-cards nor the multivariate normal model can be used to make predictions, making it unlikely that either could be used to draw general conclusions about more complex and realistic models.

Egg-laying site, fecundity and degree of sexual size dimorphism in frogs

2020 ◽  
Vol 131 (3) ◽  
pp. 600-610
Author(s):  
Nelson Rodrigues Silva ◽  
Bianca V M Berneck ◽  
Helio R da Silva ◽  
Célio F B Haddad ◽  
Kelly R Zamudio ◽  
...  
Keyword(s):  
Sexual Size Dimorphism ◽  
Egg Laying ◽  
Female Size ◽  
Selective Force ◽  
Size Dimorphism ◽  
Body Sizes ◽  
Space Limitation ◽  
Males And Females ◽  
Similar Body ◽  
Oviposition Sites

Abstract Female fecundity is an important selective force leading to female-biased sexual size dimorphism (SSD) in frogs. Because anurans exhibit diverse reproductive modes, we investigated whether variation in SSD and fecundity are related with oviposition site. We asked whether arboreal breeding species show pronounced female-biased SSD and if, paradoxically, females have lower fecundity because of the costs of carrying oocytes and amplectant males. Conversely, we tested whether species that deposit eggs in concealed sites show less pronounced SSD, because females do not carry males and space limitation may reduce female size and fecundity. Our results showed that, in general, males were approximately 20% smaller than females. However, for species with hidden oviposition sites, males and females exhibited more similar body sizes and arboreal hylids showed more pronounced female-biased SSD. Overall, fecundity was higher in aquatic breeders, as expected, but in hylids, fecundity was smaller in arboreal breeders, which suggests that arboreality may impose restrictions on fecundity. By analysing SSD in a broader and more specific lineage (Hylidae), we found that reproductive microhabitat may also influence female size and fecundity, playing an important role in the evolution of SSD in frogs at different evolutionary scales.

scholarly journals The statistical mechanics of a polygenic character under stabilizing selection, mutation and drift

2010 ◽  
Vol 8 (58) ◽  
pp. 720-739 ◽  
Author(s):  
Harold P. de Vladar ◽  
Nick H. Barton
Keyword(s):  
Population Genetics ◽  
Statistical Mechanics ◽  
Generating Function ◽  
Genetic Drift ◽  
Infinite Series ◽  
Genetic Variance ◽  
Directional Selection ◽  
Entropy Measure ◽  
Stabilizing Selection ◽  
Approximation Procedure

By exploiting an analogy between population genetics and statistical mechanics, we study the evolution of a polygenic trait under stabilizing selection, mutation and genetic drift. This requires us to track only four macroscopic variables, instead of the distribution of all the allele frequencies that influence the trait. These macroscopic variables are the expectations of: the trait mean and its square, the genetic variance, and of a measure of heterozygosity, and are derived from a generating function that is in turn derived by maximizing an entropy measure. These four macroscopics are enough to accurately describe the dynamics of the trait mean and of its genetic variance (and in principle of any other quantity). Unlike previous approaches that were based on an infinite series of moments or cumulants, which had to be truncated arbitrarily, our calculations provide a well-defined approximation procedure. We apply the framework to abrupt and gradual changes in the optimum, as well as to changes in the strength of stabilizing selection. Our approximations are surprisingly accurate, even for systems with as few as five loci. We find that when the effects of drift are included, the expected genetic variance is hardly altered by directional selection, even though it fluctuates in any particular instance. We also find hysteresis, showing that even after averaging over the microscopic variables, the macroscopic trajectories retain a memory of the underlying genetic states.

Why breed early? A study of reproductive tactics in Peromyscus

1977 ◽  
Vol 55 (5) ◽  
pp. 862-871 ◽  
Author(s):  
Daphne J. Fairbairn
Keyword(s):  
British Columbia ◽  
Reproductive Success ◽  
Peromyscus Maniculatus ◽  
Frequent Occurrence ◽  
Deer Mice ◽  
Reproductive Tactics ◽  
Selection Pressures ◽  
Bimodal Pattern ◽  
Early Peak ◽  
Males And Females

Female deer mice (Peromyscus maniculatus) near Vancouver, British Columbia, were found to have a bimodal pattern of breeding. This paper compares the success of females that attempted to breed in the early peak of breeding with that of females that did not breed until the later breeding peak. While the average success was about the same for the two tactics, early breeding had a much higher variance. It is suggested that this difference in variances would result in eventual elimination of the early-breeding phenotype, unless it were favored by other factors. Differences in the selection pressures on males and females, and the relatively frequent occurrence of years of good reproductive success for early-breeding females, may contribute to the maintenance of this phenotype in the population. A hypothesis is presented to explain both the bimodality of the breeding pattern, and the dominance of the second breeding peak.

Observations on Males and Females of Sitophilus granarius (L.), the Granary Weevil, GG Strain, Exposed for Six Generations to Allethrin and Piperonyl Butoxide

1961 ◽  
Vol 93 (7) ◽  
pp. 545-552 ◽  
Author(s):  
C. Sevintuna ◽  
A. J. Musgrave
Keyword(s):  
Insect Resistance ◽  
Specific Resistance ◽  
Regression Line ◽  
Sitophilus Granarius ◽  
Recent Discussion ◽  
Granary Weevil ◽  
The Subject ◽  
Sublethal Doses ◽  
Males And Females ◽  
Genetic Phenomenon

In a recent discussion of the subject of insect resistance to insecticides, Brown (1958) has claimed that true resistance is characterized by a five-fold to ten-fold decrease in susceptibility. It is a genetic phenomenon arising as a result of selection. There is no evidence that insecticides are mutagenic, nor can resistance be induced by exposing insects to sublethal doses. A decrease in susceptibility that cannot be regarded as resistance is regarded as a condition of tolerance. In addition, the term “vigour tolerance”, intioduced by Hoskins and Gordon (see Brown, 1958) defines instances of enhanced tolerance due to extra vigour: true specific resistance is marked by a change of slope in the dosage-mortality regression line, while “vigour tolerance” is suggested if the regression line shifts but does not change in slope.

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