6. Sexual conflict

2018 ◽  
pp. 88-103
Author(s):  
Leigh W. Simmons
Keyword(s):  
Sexual Selection ◽  
Sexual Conflict ◽  
Arms Race ◽  
Arms Races ◽  
Antagonistic Selection ◽  
Before And After ◽  
Sexually Antagonistic Selection ◽  
Males And Females ◽  
Evolutionary Consequences

The reproductive interests of males and females will almost always differ, for example over whether to mate and how often, when to produce offspring and how many, or how much to invest in each offspring. Whenever the reproductive interests of males and females differ, opposing selection on males and females to achieve their preferred outcome will generate sexually antagonistic selection. Such sexual conflict is reflected in differences in the appearance and behaviour of the sexes as each evolves to gain the advantage in a fitness ‘arms race’. ‘Sexual conflict’ explores the evolutionary consequences of these arms races in the context of sexual selection as it occurs both before and after mating.

Reproductive behavior

2018 ◽  
Author(s):  
Rachel Olzer ◽  
Rebecca L. Ehrlich ◽  
Justa L. Heinen-Kay ◽  
Jessie Tanner ◽  
Marlene Zuk
Keyword(s):  
Sexual Selection ◽  
Sexual Conflict ◽  
Female Choice ◽  
Reproductive Behavior ◽  
Mating Systems ◽  
Insect Behavior ◽  
Sequential Approach ◽  
Evolutionary Mechanisms ◽  
Anatomy And Physiology ◽  
Males And Females

Sex and reproduction lie at the heart of studies of insect behavior. We begin by providing a brief overview of insect anatomy and physiology, followed by an introduction to the overarching themes of parental investment, sexual selection, and mating systems. We then take a sequential approach to illustrate the diversity of phenomena and concepts behind insect reproductive behavior from pre-copulatory mate signalling through copulatory sperm transfer, mating positions, and sexual conflict, to post-copulatory sperm competition, and cryptic female choice. We provide an overview of the evolutionary mechanisms driving reproductive behavior. These events are linked by the economic defendability of mates or resources, and how these are allocated in each sex. Under the framework of economic defendability, the reader can better understand how sexual antagonistic behaviors arise as the result of competing optimal fitness strategies between males and females.

scholarly journals Sexual selection after gamete release in broadcast spawning invertebrates

2020 ◽  
Vol 375 (1813) ◽  
pp. 20200069 ◽  
Author(s):  
Jonathan P. Evans ◽  
Rowan A. Lymbery
Keyword(s):  
Sexual Selection ◽  
Mate Choice ◽  
Sperm Competition ◽  
Sexual Conflict ◽  
Gamete Release ◽  
Theme Issue ◽  
Animal Kingdom ◽  
External Fertilization ◽  
Broadcast Spawning ◽  
Males And Females

Broadcast spawning invertebrates offer highly tractable models for evaluating sperm competition, gamete-level mate choice and sexual conflict. By displaying the ancestral mating strategy of external fertilization, where sexual selection is constrained to act after gamete release, broadcast spawners also offer potential evolutionary insights into the cascade of events that led to sexual reproduction in more ‘derived’ groups (including humans). Moreover, the dynamic reproductive conditions faced by these animals mean that the strength and direction of sexual selection on both males and females can vary considerably. These attributes make broadcast spawning invertebrate systems uniquely suited to testing, extending, and sometimes challenging classic and contemporary ideas in sperm competition, many of which were first captured in Parker's seminal papers on the topic. Here, we provide a synthesis outlining progress in these fields, and highlight the burgeoning potential for broadcast spawners to provide both evolutionary and mechanistic understanding into gamete-level sexual selection more broadly across the animal kingdom. This article is part of the theme issue ‘Fifty years of sperm competition’.

scholarly journals Contrasting effects of intralocus sexual conflict on sexually antagonistic coevolution

2016 ◽  
Vol 113 (8) ◽  
pp. E978-E986 ◽  
Author(s):  
Tanya M. Pennell ◽  
Freek J. H. de Haas ◽  
Edward H. Morrow ◽  
G. Sander van Doorn
Keyword(s):  
Sexual Conflict ◽  
Genetic Model ◽  
Arms Races ◽  
Female Partners ◽  
Intralocus Sexual Conflict ◽  
Antagonistic Coevolution ◽  
Evolutionary Conflict ◽  
Quantitative Genetic Model ◽  
Female Specific ◽  
Evolutionary Consequences

Evolutionary conflict between the sexes can induce arms races in which males evolve traits that are detrimental to the fitness of their female partners, and vice versa. This interlocus sexual conflict (IRSC) has been proposed as a cause of perpetual intersexual antagonistic coevolution with wide-ranging evolutionary consequences. However, theory suggests that the scope for perpetual coevolution is limited, if traits involved in IRSC are subject to pleiotropic constraints. Here, we consider a biologically plausible form of pleiotropy that has hitherto been ignored in treatments of IRSC and arrive at drastically different conclusions. Our analysis is based on a quantitative genetic model of sexual conflict, in which genes controlling IRSC traits have side effects in the other sex, due to incompletely sex-limited gene expression. As a result, the genes are exposed to intralocus sexual conflict (IASC), a tug-of-war between opposing male- and female-specific selection pressures. We find that the interaction between the two forms of sexual conflict has contrasting effects on antagonistic coevolution: Pleiotropic constraints stabilize the dynamics of arms races if the mating traits are close to evolutionary equilibrium but can prevent populations from ever reaching such a state. Instead, the sexes are drawn into a continuous cycle of arms races, causing the buildup of IASC, alternated by phases of IASC resolution that trigger the next arms race. These results encourage an integrative perspective on the biology of sexual conflict and generally caution against relying exclusively on equilibrium stability analysis.

scholarly journals Macroevolutionary consequences of sexual conflict

2018 ◽  
Vol 14 (6) ◽  
pp. 20180186
Author(s):  
Jo S. Hermansen ◽  
Jostein Starrfelt ◽  
Kjetil L. Voje ◽  
Nils C. Stenseth
Keyword(s):  
Sexual Selection ◽  
Genetic Architecture ◽  
Time Frame ◽  
Sexual Conflicts ◽  
Males And Females ◽  
Selection For ◽  
Evolutionary Consequences ◽  
Future Work ◽  
Shared Genetic

Intralocus sexual conflicts arise whenever the fitness optima for a trait expressed in both males and females differ between the sexes and shared genetic architecture constrains the sexes from evolving independently towards their respective optima. Such sexual conflicts are commonplace in nature, yet their long-term evolutionary consequences remain unexplored. Using a Bayesian phylogenetic comparative framework, we studied the macroevolutionary dynamics of intersexual trait integration in stalk-eyed flies (Diopsidae) spanning a time frame of more than 25 Myr. We report that increased intensity of sexual selection on male eyestalks is associated with reduced intersexual eyestalk integration, as well as sex-specific rates of eyestalk evolution. Despite this, lineages where males have been under strong sexual selection for millions of years still exhibit high levels of intersexual trait integration. This low level of decoupling between the sexes may indicate that exaggerated female eyestalks are in fact adaptive—or alternatively, that there are strong constraints on reducing trait integration between the sexes. Future work should seek to clarify the relative roles of constraints and selection in contributing to the varying levels of intersexual trait integration in stalk-eyed flies, and in this way clarify whether sexual conflicts can act as constraints on adaptive evolution even on macroevolutionary time scales.

Sexual conflict inGerris gillettei(Insecta: Hemiptera): influence of effective mating rate and morphology on reproductive success

2012 ◽  
Vol 90 (11) ◽  
pp. 1297-1306 ◽  
Author(s):  
Marie-Claude Gagnon ◽  
Pierre Duchesne ◽  
Julie Turgeon
Keyword(s):  
Sexual Selection ◽  
Reproductive Success ◽  
Sexual Conflict ◽  
Water Strider ◽  
Mating Rate ◽  
Multiple Matings ◽  
Males And Females ◽  
Genetic Mating System ◽  
Selection Framework ◽  
Resistance Traits

In water striders, the interests of both sexes diverge over the decision to mate, leading to precopulatory sexual conflict. The influence of mating rate and key persistence and resistance traits on reproductive success has seldom been investigated in the context of multiple matings. We used amplified fragment length polymorphism (AFLP) based genetic parentage analyses to estimate mating and reproductive success in Gerris gillettei Lethierry and Severin, 1896, while allowing for free multiple matings. We tested the hypotheses that males should display stronger opportunity for sexual selection and steeper Bateman gradients. In each sex, persistence and resistance traits should also impact mating and reproductive success. Surprisingly, males and females had similarly high and variable effective mating rates (i.e., number of genetic partners), and both sexes produce more offspring when mating with more partners. As predicted, exaggerated persistence traits allowed males to mate with more partners and sire more offspring. However, we found no evidence for an impact of resistance traits for females. The mating environment may have favoured low resistance in females, but high promiscuity can be beneficial for females. This first description of the genetic mating system for a water strider species suggests that the determinants of fitness can be further deciphered using the sexual selection framework.

scholarly journals Sexual conflict mediated by ecological sex differences can generate diverse patterns of transgenerational plasticity

2019 ◽  
Author(s):  
Nathan William Burke ◽  
Shinichi Nakagawa ◽  
Russell Bonduriansky
Keyword(s):  
Sex Differences ◽  
Sexual Selection ◽  
Sexual Conflict ◽  
Evolutionary Mechanisms ◽  
Transgenerational Plasticity ◽  
Wide Range ◽  
Sex Limitation ◽  
Sexually Antagonistic Selection ◽  
And Performance ◽  
Health Cognition

ABSTRACTTransgenerational plasticity (TGP) occurs when the environment experienced by parents induces changes in traits of offspring and/or subsequent generations. Such effects can be adaptive or non-adaptive and are increasingly recognised as key determinants of health, cognition, development and performance across a wide range of taxa, including humans. While the conditions that favour maternal TGP are well understood, rapidly accumulating evidence indicates that TGP can be maternal or paternal, and offspring responses can be sex-specific. However, the evolutionary mechanisms that drive this diversity are unknown. We used an individual-based model to investigate the evolution of TGP when the sexes experience different ecologies. We find that adaptive TGP rarely evolves when alleles at loci that determine offspring responses to environmental information originating from the mother and father are subject to sexually antagonistic selection. By contrast, duplication and sex-limitation of such loci can allow for the evolution of a variety of sex-specific responses, including non-adaptive sex-specific TGP when sexual selection is strong. Sexual conflict could therefore help to explain why adaptive TGP evolves in some species but not others, why sons and daughters respond to parental signals in different ways, and why complex patterns of sex-specific TGP may often be non-adaptive.

scholarly journals Stable linkage disequilibrium owing to sexual antagonism

2010 ◽  
Vol 278 (1707) ◽  
pp. 855-862 ◽  
Author(s):  
Francisco Úbeda ◽  
David Haig ◽  
Manus M. Patten
Keyword(s):  
Linkage Disequilibrium ◽  
Genomic Structure ◽  
Natural Populations ◽  
Allele Frequencies ◽  
Population Subdivision ◽  
Sexual Antagonism ◽  
Antagonistic Selection ◽  
Sexually Antagonistic Selection ◽  
Males And Females ◽  
Frequent Observation

Linkage disequilibrium (LD) is an association between genetic loci that is typically transient. Here, we identify a previously overlooked cause of stable LD that may be pervasive: sexual antagonism. This form of selection produces unequal allele frequencies in males and females each generation, which upon admixture at fertilization give rise to an excess of haplotypes that couple male-beneficial with male-beneficial and female-beneficial with female-beneficial alleles. Under sexual antagonism, LD is obtained for all recombination frequencies in the absence of epistasis. The extent of LD is highest at low recombination and for stronger selection. We provide a partition of the total LD into distinct components and compare our result for sexual antagonism with Li and Nei's model of LD owing to population subdivision. Given the frequent observation of sexually antagonistic selection in natural populations and the number of traits that are often involved, these results suggest a major contribution of sexual antagonism to genomic structure.

scholarly journals Sexually antagonistic selection promotes genetic divergence between males and females in an ant

2019 ◽  
Vol 116 (48) ◽  
pp. 24157-24163 ◽  
Author(s):  
Pierre-André Eyer ◽  
Alexander J. Blumenfeld ◽  
Edward L. Vargo
Keyword(s):  
Sex Chromosomes ◽  
Hot Spot ◽  
Genetic Bottleneck ◽  
Invasion Success ◽  
Invasive Ant ◽  
Antagonistic Selection ◽  
Nylanderia Fulva ◽  
Hymenopteran Species ◽  
Sexually Antagonistic Selection ◽  
Males And Females

Genetic diversity acts as a reservoir for potential adaptations, yet selection tends to reduce this diversity over generations. However, sexually antagonistic selection (SAS) may promote diversity by selecting different alleles in each sex. SAS arises when an allele is beneficial to one sex but harmful to the other. Usually, the evolution of sex chromosomes allows each sex to independently reach different optima, thereby circumventing the constraint of a shared autosomal genome. Because the X chromosome is found twice as often in females than males, it represents a hot spot for SAS, offering a refuge for recessive male-beneficial but female-costly alleles. Hymenopteran species do not have sex chromosomes; females are diploid and males are haploid, with sex usually determined by heterozygosity at the complementary sex-determining locus. For this reason, their entire genomes display an X-linked pattern, as every chromosome is found twice as often in females than in males, which theoretically predisposes them to SAS in large parts of their genome. Here we report an instance of sexual divergence in the Hymenoptera, a sexually reproducing group that lacks sex chromosomes. In the invasive ant Nylanderia fulva, a postzygotic SAS leads daughters to preferentially carry alleles from their mothers and sons to preferentially carry alleles from their grandfathers for a substantial region (∼3%) of the genome. This mechanism results in nearly all females being heterozygous at these regions and maintains diversity throughout the population, which may mitigate the effects of a genetic bottleneck following introduction to an exotic area and enhance the invasion success of this ant.

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