scholarly journals Assessing sex-specific selection against deleterious alleles: males don’t pay for sex

2016 ◽  
Author(s):  
Zofia M. Prokop ◽  
Monika A. Prus ◽  
Tomasz S. Gaczorek ◽  
Karolina Markot ◽  
Joanna K. Palka ◽  
...  
Keyword(s):  
Sexual Selection ◽  
Mutation Load ◽  
Induced Mutations ◽  
Relative Contribution ◽  
Deleterious Alleles ◽  
Flour Beetles ◽  
Novel Approach ◽  
Evolutionary Force ◽  
Hypothetical Scenario ◽  
Asexual Populations

AbstractSelection acting on males can reduce mutation load of sexual relative to asexual populations, thus mitigating the two-fold cost of sex. This requires that it seeks and destroys the same mutations as selection acting on females, but with higher efficiency, which could happen due to sexual selection-a potent evolutionary force that in most systems predominantly affects males. We used replicate populations of red flour beetles (Tribolium castaneum) to study sex-specific selection against deleterious mutations introduced with ionizing radiation. Additionally, we employed a novel approach to quantify the relative contribution of sexual selection to the overall selection observed in males. The induced mutations were selected against in both sexes, with decreased sexual competitiveness contributing, on average, over 40% of the total decline in male fitness. However, we found no evidence for selection being stronger in males than in females; in fact, we observed a non-significant trend in the opposite direction. These results suggest that selection on males does not reduce mutation load below the level expected under the (hypothetical) scenario of asexual reproduction. Thus, we found no support for the hypothesis that sexual selection contributes to the evolutionary maintenance of sex.

scholarly journals Sexual selection and inbreeding: two efficient ways to limit the accumulation of deleterious mutations

2018 ◽  
Author(s):  
E. Noël ◽  
E. Fruitet ◽  
D. Lelaurin ◽  
N. Bonel ◽  
A. Ségard ◽  
...  
Keyword(s):  
Sexual Selection ◽  
Experimental Evolution ◽  
Genetic Load ◽  
Deleterious Mutations ◽  
Mutation Load ◽  
Male Function ◽  
Female Function ◽  
Deleterious Alleles ◽  
Self Fertilization ◽  
Male Specific

AbstractTheory and empirical data showed that two processes can boost selection against deleterious mutations, thus facilitating the purging of the mutation load: inbreeding, by exposing recessive deleterious alleles to selection in homozygous form, and sexual selection, by enhancing the relative reproductive success of males with small mutation loads. These processes tend to be mutually exclusive because sexual selection is reduced under mating systems that promote inbreeding, such as self-fertilization in hermaphrodites. We estimated the relative efficiency of inbreeding and sexual selection at purging the genetic load, using 50 generations of experimental evolution, in a hermaphroditic snail (Physa acuta). To this end, we generated lines that were exposed to various intensities of inbreeding, sexual selection (on the male function) and nonsexual selection (on the female function). We measured how these regimes affected the mutation load, quantified through the survival of outcrossed and selfed juveniles. We found that juvenile survival strongly decreased in outbred lines with reduced male selection, but not when female selection was relaxed, showing that male-specific sexual selection does purge deleterious mutations. However, in lines exposed to inbreeding, where sexual selection was also relaxed, survival did not decrease, and even increased for self-fertilized juveniles, showing that purging through inbreeding can compensate for the absence of sexual selection. Our results point to the further question of whether a mixed strategy combining the advantages of both mechanisms of genetic purging could be evolutionary stable.

scholarly journals The Effect of Deleterious Alleles on Adaptation in Asexual Populations

Genetics ◽  
2002 ◽  
Vol 162 (1) ◽  
pp. 395-411 ◽  
Author(s):  
Toby Johnson ◽  
Nick H Barton
Keyword(s):  
Selective Sweep ◽  
Deleterious Mutation ◽  
Short Interval ◽  
Selective Advantage ◽  
Asexual Population ◽  
Restrictive Assumption ◽  
Deleterious Alleles ◽  
Fixation Probabilities ◽  
Asexual Populations ◽  
Beneficial Allele

Abstract We calculate the fixation probability of a beneficial allele that arises as the result of a unique mutation in an asexual population that is subject to recurrent deleterious mutation at rate U. Our analysis is an extension of previous works, which make a biologically restrictive assumption that selection against deleterious alleles is stronger than that on the beneficial allele of interest. We show that when selection against deleterious alleles is weak, beneficial alleles that confer a selective advantage that is small relative to U have greatly reduced probabilities of fixation. We discuss the consequences of this effect for the distribution of effects of alleles fixed during adaptation. We show that a selective sweep will increase the fixation probabilities of other beneficial mutations arising during some short interval afterward. We use the calculated fixation probabilities to estimate the expected rate of fitness improvement in an asexual population when beneficial alleles arise continually at some low rate proportional to U. We estimate the rate of mutation that is optimal in the sense that it maximizes this rate of fitness improvement. Again, this analysis relaxes the assumption made previously that selection against deleterious alleles is stronger than on beneficial alleles.

scholarly journals Natural selection increases female fitness by reversing the exaggeration of a male sexually selected trait

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Kensuke Okada ◽  
Masako Katsuki ◽  
Manmohan D. Sharma ◽  
Katsuya Kiyose ◽  
Tomokazu Seko ◽  
...  
Keyword(s):  
Sexual Selection ◽  
Natural Selection ◽  
Experimental Evolution ◽  
Genetic Correlations ◽  
Lifetime Reproductive Success ◽  
Fundamental Theory ◽  
Female Fitness ◽  
Male Trait ◽  
Flour Beetles ◽  
Male Specific

AbstractTheory shows how sexual selection can exaggerate male traits beyond naturally selected optima and also how natural selection can ultimately halt trait elaboration. Empirical evidence supports this theory, but to our knowledge, there have been no experimental evolution studies directly testing this logic, and little examination of possible associated effects on female fitness. Here we use experimental evolution of replicate populations of broad-horned flour beetles to test for effects of sex-specific predation on an exaggerated sexually selected male trait (the mandibles), while also testing for effects on female lifetime reproductive success. We find that populations subjected to male-specific predation evolve smaller sexually selected mandibles and this indirectly increases female fitness, seemingly through intersexual genetic correlations we document. Predation solely on females has no effects. Our findings support fundamental theory, but also reveal unforseen outcomes—the indirect effect on females—when natural selection targets sex-limited sexually selected characters.

scholarly journals Selection, Load and Inbreeding Depression in a Large Metapopulation

Genetics ◽  
2002 ◽  
Vol 160 (3) ◽  
pp. 1191-1202 ◽  
Author(s):  
Michael C Whitlock
Keyword(s):  
Population Structure ◽  
Inbreeding Depression ◽  
Population Subdivision ◽  
Response To Selection ◽  
Mutation Load ◽  
Deleterious Alleles ◽  
Subdivided Population ◽  
Soft Selection ◽  
Mean Fitness ◽  
The Mean

Abstract The subdivision of a species into local populations causes its response to selection to change, even if selection is uniform across space. Population structure increases the frequency of homozygotes and therefore makes selection on homozygous effects more effective. However, population subdivision can increase the probability of competition among relatives, which may reduce the efficacy of selection. As a result, the response to selection can be either increased or decreased in a subdivided population relative to an undivided one, depending on the dominance coefficient FST and whether selection is hard or soft. Realistic levels of population structure tend to reduce the mean frequency of deleterious alleles. The mutation load tends to be decreased in a subdivided population for recessive alleles, as does the expected inbreeding depression. The magnitude of the effects of population subdivision tends to be greatest in species with hard selection rather than soft selection. Population structure can play an important role in determining the mean fitness of populations at equilibrium between mutation and selection.

scholarly journals Sexual selection and sexual size dimorphism in animals

2021 ◽  
Vol 17 (9) ◽  
pp. 20210251
Author(s):  
Tim Janicke ◽  
Salomé Fromonteil
Keyword(s):  
Sexual Selection ◽  
Sex Difference ◽  
Positive Relationship ◽  
Sexual Size Dimorphism ◽  
Effect Sizes ◽  
Size Dimorphism ◽  
Bateman Gradient ◽  
Mixed Support ◽  
Evolutionary Force ◽  
Length Measurements

Sexual selection is often considered as a critical evolutionary force promoting sexual size dimorphism (SSD) in animals. However, empirical evidence for a positive relationship between sexual selection on males and male-biased SSD received mixed support depending on the studied taxonomic group and on the method used to quantify sexual selection. Here, we present a meta-analytic approach accounting for phylogenetic non-independence to test how standardized metrics of the opportunity and strength of pre-copulatory sexual selection relate to SSD across a broad range of animal taxa comprising up to 95 effect sizes from 59 species. We found that SSD based on length measurements was correlated with the sex difference in the opportunity for sexual selection but showed a weak and statistically non-significant relationship with the sex difference in the Bateman gradient. These findings suggest that pre-copulatory sexual selection plays a limited role for the evolution of SSD in a broad phylogenetic context.

scholarly journals Sexual Selection Does Not Increase the Rate of Compensatory Adaptation to a Mutation Influencing a Secondary Sexual Trait in Drosophila melanogaster

2020 ◽  
Vol 10 (5) ◽  
pp. 1541-1551
Author(s):  
Christopher H. Chandler ◽  
Anna Mammel ◽  
Ian Dworkin
Keyword(s):  
Drosophila Melanogaster ◽  
Sexual Selection ◽  
Natural Selection ◽  
Spontaneous Mutation ◽  
Phenotypic Expression ◽  
Theoretical Work ◽  
Phenotypic Suppression ◽  
Compensatory Adaptation ◽  
Deleterious Alleles ◽  
Sex Comb

Theoretical work predicts that sexual selection can enhance natural selection, increasing the rate of adaptation to new environments and helping purge harmful mutations. While some experiments support these predictions, remarkably little work has addressed the role of sexual selection on compensatory adaptation—populations’ ability to compensate for the costs of deleterious alleles that are already present. We tested whether sexual selection, as well as the degree of standing genetic variation, affect the rate of compensatory evolution via phenotypic suppression in experimental populations of Drosophila melanogaster. These populations were fixed for a spontaneous mutation causing mild abnormalities in the male sex comb, a structure important for mating success. We fine-mapped this mutation to an ∼85 kb region on the X chromosome containing three candidate genes, showed that the mutation is deleterious, and that its phenotypic expression and penetrance vary by genetic background. We then performed experimental evolution, including a treatment where opportunity for mate choice was limited by experimentally enforced monogamy. Although evolved populations did show some phenotypic suppression of the morphological abnormalities in the sex comb, the amount of suppression did not depend on the opportunity for sexual selection. Sexual selection, therefore, may not always enhance natural selection; instead, the interaction between these two forces may depend on additional factors.

Behavioural and genetic analyses of mate choice and reproductive success in two Chinook salmon populations

2013 ◽  
Vol 70 (2) ◽  
pp. 263-270 ◽  
Author(s):  
Melissa L. Evans ◽  
Bryan D. Neff ◽  
Daniel D. Heath
Keyword(s):  
Sexual Selection ◽  
Natural Selection ◽  
Reproductive Success ◽  
Mate Choice ◽  
Mhc Class Ii ◽  
Chinook Salmon ◽  
Oncorhynchus Tshawytscha ◽  
Mating Behaviour ◽  
Selection Pressures ◽  
Evolutionary Force

Sexual selection is recognized as an important evolutionary force in salmon. However, relatively little is known about variation in sexual selection pressures across salmon populations or the potential role of natural selection as a driver of adaptive mating patterns. Here, we examine mating behaviour and correlates of reproductive success in Chinook salmon (Oncorhynchus tshawytscha) from the Quinsam and Little Qualicum rivers in British Columbia, Canada — two populations for which we have previously found evidence of natural selection operating on major histocompatibility complex (MHC) genes. In both populations, males courted females and exhibited dominance behaviour towards other males, and the frequency of each behaviour was positively associated with reproductive success. Males were more aggressive towards females with whom they would produce offspring of low or high MHC class II diversity, and the offspring of males from the Quinsam River exhibited higher diversity at the MHC class I than expected. We discuss our results in relation to local natural selection pressures on the MHC and the potential for MHC-dependent mate choice.

Titrating haemophilia B phenotypes using siRNA strategy: evidence that antithrombotic activity is separated from bleeding liability

2015 ◽  
Vol 113 (06) ◽  
pp. 1300-1311 ◽  
Author(s):  
Anil Thankappan ◽  
Walter R. Strapps ◽  
Marti DiPietro ◽  
Karen Leander ◽  
Zuo Zhang ◽  
...  
Keyword(s):  
Target Gene ◽  
Gene Knockout ◽  
Coagulation Factor ◽  
Coagulation Factors ◽  
Factor Ix ◽  
Antithrombotic Activity ◽  
Relative Contribution ◽  
Treatment And Prevention ◽  
Novel Approach ◽  
Gene Mrna

SummaryHaemophilia A and B are characterised by a life-long bleeding predisposition, and several lines of evidence suggest that risks of atherothrombotic events may also be reduced. Establishing a direct correlation between coagulation factor levels, thrombotic risks and bleeding propensity has long been hampered by an inability to selectively and specifically inhibit coagulation factor levels. Here, the exquisite selectivity of gene silencing combined with a gene knockout (KO) approach was used to define the relative contribution of factor IX (fIX) to thrombosis and primary haemostasis in the rat. Using a lipid nanoparticle (LNP) formulation, we successfully delivered fIX siRNAs to the liver by intravenous administration. The knockdown (KD) of target gene mRNA was achieved rapidly (within 24 hour post-siRNA dosing), sustained (maintained for at least 7 days post dosing) and not associated with changes in mRNA expression levels of other coagulation factors. We found that intermediate levels of liver fIX mRNA silencing (60–95 %) translating into a 50–99 % reduction of plasma fIX activity provided protection from thrombosis without prolonging the cuticle bleeding time. Over 99 % inhibition of fIX activity was required to observe increase in bleeding, a phenotype confirmed in fIX KO rats. These data provide substantial evidence of a participation of fIX in the mechanisms regulating thrombosis prior to those regulating primary haemostasis, therefore highlighting the potential of fIX as a therapeutic target. In addition, hepatic mRNA silencing using LNP-encapsulated siRNAs may represent a promising novel approach for the chronic treatment and prevention of coagulation-dependent thrombotic disorders in humans.

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