Sexual selection and its effect on the fixation of an asexual clone

Marcel Salathé

doi:10.1098/rsbl.2006.0529

Sexual selection and its effect on the fixation of an asexual clone

Biology Letters ◽

10.1098/rsbl.2006.0529 ◽

2006 ◽

Vol 2 (4) ◽

pp. 536-538 ◽

Cited By ~ 4

Author(s):

Marcel Salathé

Keyword(s):

Sexual Selection ◽

Sexual Reproduction ◽

Mutation Rates ◽

Male Mating ◽

Mutational Load ◽

Deleterious Mutations ◽

Sexual Population ◽

Fitness Advantage ◽

Genomic Mutation ◽

Cost Of Sex

Sexual selection is a powerful and ubiquitous force in sexual populations. It has recently been argued that sexual selection can eliminate the twofold cost of sex even with low genomic mutation rates. By means of differential male mating success, deleterious mutations in males become more deleterious than in females, and it has been shown that sexual selection can drastically reduce the mutational load in a sexual population, with or without any form of epistasis. However, any mechanism that claims to maintain sexual reproduction must be able to prevent the fixation of an asexual mutant clone with a twofold fitness advantage. Here, I show that despite very strong sexual selection, the fixation of an asexual mutant cannot be prevented under reasonable genomic mutation rates. Sexual selection can have a strong effect on the average mutational load in a sexual population, but as it cannot prevent the fixation of an asexual mutant, it is unlikely to play a key role on the maintenance of sexual reproduction.

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Sexual selection can reduce mutational load in Drosophila subobscura

Genetika ◽

10.2298/gensr1302537v ◽

2013 ◽

Vol 45 (2) ◽

pp. 537-552 ◽

Cited By ~ 3

Author(s):

Marija Savic-Veselinovic ◽

Sofija Pavkovic-Lucic ◽

Zorana Kurbalija-Novicic ◽

Mihailo Jelic ◽

Marko Andjelkovic

Keyword(s):

Sexual Selection ◽

Sexual Conflict ◽

Male Mating ◽

Mutational Load ◽

Genetic Quality ◽

Genetic Structure Of Populations ◽

Deleterious Alleles ◽

Theoretical Predictions ◽

Set Up ◽

Genetic Pool

According to theoretical predictions sexual selection can reduce mutational load through male mating success. Males of good genetic quality should be more successful in matings, compared to the males of low genetic quality, thus in this way females can prevent deleterious alleles to be transmitted to the next generation. We tested this hypothesis through set up of two experimental groups from same genetic pool, where in one group genetic quality was manipulated by ionizing radiation. Within each group opportunity for choosing mates was imposed: males and females had no choice or had multiple choice. Mutational load was measured through the variability of different fitness components: fecundity and egg-to-adult viability. Our results indicate that sexual selection can reduce mutational load, only for fecundity. Group with the presence of female choice exhibited higher fecundity than group in which sexual selection was experimentally eliminated, but only in ?irradiated? group. There was no overall difference in egg-to-adult viability between different sexual selection regimes in any of the group. It should be considered that sexual selection can cause sexual conflict, and potential opposite effects of sexual selection and sexual conflict on fitness. Genetic structure of populations, in terms of the level of mutational load, is an important factor which can determinate the role of sexual selection.

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Sexual selection for rare beneficial mutations promotes the evolution of sexual reproduction and adaptation

10.1101/2021.05.25.445661 ◽

2021 ◽

Author(s):

Gilbert Roberts ◽

Marion Petrie

Keyword(s):

Sexual Selection ◽

Sexual Reproduction ◽

Negative Impact ◽

Reproductive Rate ◽

Beneficial Mutations ◽

Selection For ◽

The Cost ◽

Average Fitness ◽

Cost Of Sex

The evolution and widespread maintenance of sexual reproduction remains a conundrum in biology because asexual reproduction should allow twice the reproductive rate. One hypothesis is that sexual selection lessens the negative impact on fitness of accumulating deleterious mutations. However, for adaptation to occur, there must also be selection for beneficial mutations. Here we show that sexual selection can help explain the evolution and maintenance of sexual reproduction. In our model, females chose males with more beneficial mutations (as opposed to just fewer harmful ones) even when these occurred much more rarely. Sexual selection thereby increased fixation of beneficial mutations which increased the absolute genetic quality of sexual offspring. This increase in fitness relative to asexual offspring adds to the previously postulated effect of reduced mutation load in offsetting the cost of sex. Analysing our simulations reveals that female choice among males raised the fitness of reproducing males above that of females. We found that this effect could overcome the decline in average fitness that occurs when mutation rate increases, allowing an increase in the fixation of beneficial mutations. Sexual selection thereby not only facilitates the evolution of sexual reproduction but maintains sex by leveraging its benefits and driving adaptation.

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Population genetic aspects of deleterious cytoplasmic genomes and their effect on the evolution of sexual reproduction

Genetics Research ◽

10.1017/s0016672300030500 ◽

1992 ◽

Vol 59 (3) ◽

pp. 215-225 ◽

Cited By ~ 69

Author(s):

Ian M. Hastings

Keyword(s):

Sexual Reproduction ◽

Host Cell ◽

Conflict Of Interest ◽

Deleterious Effect ◽

Standard Theory ◽

Uniparental Inheritance ◽

Sexual Population ◽

Intracellular Parasites ◽

The Cost ◽

Cost Of Sex

SummaryA conflict of interest may arise between intra-cellular genomes and their host cell. The example explicitly investigated is that of a ‘selfish’ mitochondrion which increases its own rate of replication at the cost of reduced metabolic activity which is deleterious to the host cell. The results apply to deleterious cytoplasmic agents in general, such as intracellular parasites. Numerical simulation suggests that selfish mitochondria are able to invade an isogamous sexual population and are capable of reducing its fitness to below “5 % of that prior to their invasion. Their spread is enhanced by decreasing the number of mitotic divisions between meioses, and this may constitute a significant constraint on the evolution of lifecycles. The presence of such deleterious cytoplasmic agents favours a nuclear mutation whose expression prevents cytoplasm from the other gamete entering the zygote at fertilization, resulting in uniparental inheritance of cytoplasm. Such a mutation appears physiologically plausible and can increase in frequency despite its deleterious effect in halving the amount of cytoplasm in the zygote. It is suggested that these were the conditions under which anisogamy evolved. These results have implications for the evolution of sexual reproduction. Standard theory suggests there is no immediate cost of sex, a twofold cost being incurred later as anisogamy evolves. The analysis described here predicts a large, rapid reduction in fitness associated with isogamous sexual reproduction, due to the spread of deleterious cytoplasmic agents with fitness only subsequently rising to a maximum twofold cost as uniparental inheritance of cytoplasm and anisogamy evolve.

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Limited Dispersal, Deleterious Mutations and the Evolution of Sex

Genetics ◽

10.1093/genetics/142.3.1053 ◽

1996 ◽

Vol 142 (3) ◽

pp. 1053-1060

Author(s):

Joel R Peck

Keyword(s):

Mathematical Model ◽

Sexual Reproduction ◽

Genetic Locus ◽

Genetic Material ◽

Plant Population ◽

Deleterious Mutations ◽

Animal Populations ◽

Offspring Sex ◽

Limited Dispersal ◽

Hermaphroditic Plant

Abstract This study presents a mathematical model that allows for some offspring to be dispersed at random, while others stay close to their mothers. A single genetic locus is assumed to control fertility, and this locus is subject to the occurrence of deleterious mutations. It is shown that, at equilibrium, the frequency of deleterious mutations in the population is inversely related to the rate of dispersal. This is because dispersal of offspring leads to enhanced competition among adults. The results also show that sexual reproduction can lead to a decrease in the equilibrium frequency of deleterious mutations. The reason for this relationship is that sex involves the dispersal of genetic material, and thus, like the dispersal of offspring, sex enhances competition among adults. The model is described using the example of a hermaphroditic plant population. However, the results should apply to animal populations as well.

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On the Rate and Linearity of Viability Declines in Drosophila Mutation-Accumulation Experiments: Genomic Mutation Rates and Synergistic Epistasis Revisited

Genetics ◽

10.1093/genetics/166.2.797 ◽

2004 ◽

Vol 166 (2) ◽

pp. 797-806 ◽

Cited By ~ 4

Author(s):

James D Fry

Keyword(s):

Mutation Rate ◽

Average Rate ◽

Natural Populations ◽

Mutation Accumulation ◽

High Rate ◽

Deleterious Mutations ◽

Order Of Magnitude ◽

Contamination Event ◽

Genomic Mutation ◽

The 1960S

Abstract High rates of deleterious mutations could severely reduce the fitness of populations, even endangering their persistence; these effects would be mitigated if mutations synergize each others’ effects. An experiment by Mukai in the 1960s gave evidence that in Drosophila melanogaster, viability-depressing mutations occur at the surprisingly high rate of around one per zygote and that the mutations interact synergistically. A later experiment by Ohnishi seemed to support the high mutation rate, but gave no evidence for synergistic epistasis. Both of these studies, however, were flawed by the lack of suitable controls for assessing viability declines of the mutation-accumulation (MA) lines. By comparing homozygous viability of the MA lines to simultaneously estimated heterozygous viability and using estimates of the dominance of mutations in the experiments, I estimate the viability declines relative to an appropriate control. This approach yields two unexpected conclusions. First, in Ohnishi’s experiment as well as in Mukai’s, MA lines showed faster-than-linear declines in viability, indicative of synergistic epistasis. Second, while Mukai’s estimate of the genomic mutation rate is supported, that from Ohnishi’s experiment is an order of magnitude lower. The different results of the experiments most likely resulted from differences in the starting genotypes; even within Mukai’s experiment, a subset of MA lines, which I argue probably resulted from a contamination event, showed much slower viability declines than did the majority of lines. Because different genotypes may show very different mutational behavior, only studies using many founding genotypes can determine the average rate and distribution of effects of mutations relevant to natural populations.

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The Advantages of Segregation and the Evolution of Sex

Genetics ◽

10.1093/genetics/164.3.1099 ◽

2003 ◽

Vol 164 (3) ◽

pp. 1099-1118 ◽

Cited By ~ 12

Author(s):

Sarah P Otto

Keyword(s):

Sexual Reproduction ◽

Asexual Reproduction ◽

Deleterious Mutations ◽

Evolution Of Sex ◽

Beneficial Mutations ◽

Selection Regime ◽

Strong Selection ◽

Genome Wide ◽

Low Levels

AbstractIn diploids, sexual reproduction promotes both the segregation of alleles at the same locus and the recombination of alleles at different loci. This article is the first to investigate the possibility that sex might have evolved and been maintained to promote segregation, using a model that incorporates both a general selection regime and modifier alleles that alter an individual’s allocation to sexual vs. asexual reproduction. The fate of different modifier alleles was found to depend strongly on the strength of selection at fitness loci and on the presence of inbreeding among individuals undergoing sexual reproduction. When selection is weak and mating occurs randomly among sexually produced gametes, reductions in the occurrence of sex are favored, but the genome-wide strength of selection is extremely small. In contrast, when selection is weak and some inbreeding occurs among gametes, increased allocation to sexual reproduction is expected as long as deleterious mutations are partially recessive and/or beneficial mutations are partially dominant. Under strong selection, the conditions under which increased allocation to sex evolves are reversed. Because deleterious mutations are typically considered to be partially recessive and weakly selected and because most populations exhibit some degree of inbreeding, this model predicts that higher frequencies of sex would evolve and be maintained as a consequence of the effects of segregation. Even with low levels of inbreeding, selection is stronger on a modifier that promotes segregation than on a modifier that promotes recombination, suggesting that the benefits of segregation are more likely than the benefits of recombination to have driven the evolution of sexual reproduction in diploids.

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Size does not matter for male Marbled Salamanders (Ambystoma opacum)

Canadian Journal of Zoology ◽

10.1139/cjz-2014-0229 ◽

2015 ◽

Vol 93 (10) ◽

pp. 735-740

Author(s):

D.A. Croshaw ◽

J.H.K. Pechmann

Keyword(s):

Sexual Selection ◽

Body Size ◽

Reproductive Success ◽

Large Male ◽

Male Mating ◽

Ambystoma Opacum ◽

Positive Assortative Mating ◽

Important Trait ◽

Breeding Groups ◽

Gravid Females

Understanding the phenotypic attributes that contribute to variance in mating and reproductive success is crucial in the study of evolution by sexual selection. In many animals, body size is an important trait because larger individuals enjoy greater fitness due to the ability to secure more mates and produce more offspring. Among males, this outcome is largely mediated by greater success in competition with rival males and (or) advantages in attractiveness to females. Here we tested the hypothesis that large male Marbled Salamanders (Ambystoma opacum (Gravenhorst, 1807)) mate with more females and produce more offspring than small males. In experimental breeding groups, we included males chosen specifically to represent a range of sizes. After gravid females mated and nested freely, we collected egg clutches and genotyped all adults and samples of hatchlings with highly variable microsatellite markers to assign paternity. Size had little effect on male mating and reproductive success. Breeding males were not bigger than nonbreeding males, mates of polyandrous females were not smaller than those of monogamous females, and there was no evidence for positive assortative mating by size. Although body size did not matter for male Marbled Salamanders, we documented considerable fitness variation and discuss alternative traits that could be undergoing sexual selection.

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Sex ratio effects on reproductive strategies in humans

Royal Society Open Science ◽

10.1098/rsos.140402 ◽

2015 ◽

Vol 2 (1) ◽

pp. 140402 ◽

Cited By ~ 53

Author(s):

Ryan Schacht ◽

Monique Borgerhoff Mulder

Keyword(s):

Sexual Selection ◽

Sex Ratio ◽

Ethnic Group ◽

Reproductive Strategies ◽

Situational Factors ◽

Male Mating ◽

Mating Effort ◽

Short Term ◽

Adult Sex Ratio ◽

Using Data

Characterizations of coy females and ardent males are rooted in models of sexual selection that are increasingly outdated. Evolutionary feedbacks can strongly influence the sex roles and subsequent patterns of sex differentiated investment in mating effort, with a key component being the adult sex ratio (ASR). Using data from eight Makushi communities of southern Guyana, characterized by varying ASRs contingent on migration, we show that even within a single ethnic group, male mating effort varies in predictable ways with the ASR. At male-biased sex ratios, men's and women's investment in mating effort are indistinguishable; only when men are in the minority are they more inclined towards short-term, low investment relationships than women. Our results support the behavioural ecological tenet that reproductive strategies are predictable and contingent on varying situational factors.

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