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1.
Inter-locus sexual conflict occurs by definition when there is sexually antagonistic selection on a trait so that the optimal trait value differs between the sexes. As a result, there is selection on each sex to manipulate the trait towards its own optimum and resist such manipulation by the other sex. Sexual conflict often leads additionally to the evolution of harmful behaviour and to self-reinforcing and even perpetual sexually antagonistic coevolution. In an attempt to understand the determinants of these different outcomes, I compare two groups of traits-those related to parental investment (PI) and to mating-over which there is sexual conflict, but which have to date been explored by largely separate research traditions. A brief review suggests that sexual conflict over PI, particularly over PI per offspring, leads less frequently to the evolution of manipulative behaviour, and rarely to the evolution of harmful behaviour or to the rapid evolutionary changes which may be symptomatic of sexually antagonistic coevolution. The chief determinants of the evolutionary outcome of sexual conflict are the benefits of manipulation and resistance, the costs of manipulation and resistance, and the feasibility of manipulation. All three of these appear to contribute to the differences in the evolutionary outcome of conflicts over PI and mating. A detailed dissection of the evolutionary changes following from sexual conflict exposes greater complexity than a simple adaptation-counter-adaptation cycle and clarifies the role of harm. Not all of the evolutionary changes that follow from sexual conflict are sexually antagonistic, and harm is not necessary for sexually antagonistic coevolution to occur. In particular, whereas selection on the trait over which there is conflict is by definition sexually antagonistic, collateral harm is usually in the interest of neither sex. This creates the opportunity for palliative adaptations which reduce collateral harm. Failure to recognize that such adaptations are in the interest of both sexes can hinder our understanding of the evolutionary outcome of sexual conflict.  相似文献   

2.
It is widely understood that the costs and benefits of mating can affect the fecundity and survival of individuals. Sexual conflict may have profound consequences for populations as a result of the negative effects it causes males and females to have on one another's fitness. Here we present a model describing the evolution of sexual conflict, in which males inflict a direct cost on female fitness. We show that these costs can drive the entire population to extinction. To males, females are an essential but finite resource over which they have to compete. Population extinction owing to sexual conflict can therefore be seen as an evolutionary tragedy of the commons. Our model shows that a positive feedback between harassment and the operational sex ratio is responsible for the demise of females and, thus, for population extinction. We further show that the evolution of female resistance to counter harassment can prevent a tragedy of the commons. Our findings not only demonstrate that sexual conflict can drive a population to extinction but also highlight how simple mechanisms, such as harassment costs to males and females and the coevolution between harassment and resistance, can help avert a tragedy of the commons caused by sexual conflict.  相似文献   

3.
The contemporary dynamics of sexually antagonistic coevolution caused by sexual conflicts have seldom been investigated at the intraspecific level. We characterized natural populations of Gerris gillettei and documented significant intersexual correlations for morphological traits previously related to sexual conflict in water striders. These results strongly indicate that sexually antagonistic coevolution contributed to population differentiation and resulted in different balances of armaments between the sexes within natural populations of this species. No-choice mating experiments further revealed that both male and male-female relative arms levels influence copulation duration. However, there were no asymmetries in reproductive behaviour and fitness between sympatric and allopatric mating pairs, suggesting that differentiation by sexual conflict was not sufficient to influence the outcome of mating interactions. Altogether, these results question the relative importance of female connexival spines vs. genitalia traits in mediating pre- and post-copulatory conflict in Gerris.  相似文献   

4.
Recent research on diverse animal taxa has revealed that male adaptations to sperm competition often lead to a conflict with female interests. That is, male attempts to increase their own fertilization success can result in a reduction of female fitness. This sexual conflict has led to selection for a variety of female adaptations that apparently reduce male-imposed costs. Understanding the causes and consequences of sexual conflict arising from adaptations to sperm competition offers much potential for new insight into the coevolution of male and female sexual strategies.  相似文献   

5.
Theory predicts that sexual conflict can fuel evolutionary change and generate substantial reproductive costs. This was tested here by measuring the fitness of focal individuals across multiple generations using an experimental framework. We manipulated sexual conflict through high versus low exposure of females to males across a four-generation pedigree of Drosophila melanogaster, and assessed fitness in 1062 females and 639 males. We used the animal model to estimate (1) genotype by sexual conflict environment interactions for female fitness and (2) indirect benefits gained through sons and daughters. Some female genotypes achieved higher fitness under low, in comparison to high, conflict and vice versa. We found a consistent 10% reduction in female fitness under high conflict, regardless of maternal history. Following high exposure, females produced sons with increased, but grandsons with decreased, fitness. This opposing effect suggests no consistent fitness gains through sons for females that mated multiply. We saw no indirect benefits through daughters. Our pedigree was based exclusively on maternal links; however, maternal effects are unlikely to contribute significantly unless expressed across multiple generations. In sum, we quantified a significant sexual conflict load and a female genotype by sexual conflict interaction that could slow the erosion of genetic variation.  相似文献   

6.
Reproduction has classically been viewed as a predominantly cooperative process. However, over the last 20 years this concept has steadily yielded ground to one of continual conflict in which the interests of the sexes are typically discordant. Within this framework, males and females are seen to be locked into a perpetual arms race, each adaptation by one sex promoting the evolution of countermeasures in the other sex. However, under strict genetic monogamy, the interests of the sexes become congruent, and hence antagonistic coevolution does not occur. We subjected the fly Sepsis cynipsea, a species with conspicuous sexual conflict, to experimentally enforced monogamy or polyandry for 29 generations and evaluated the microevolutionary consequences. We found that there were longevity costs to females consistent with sexually antagonistic coevolution. However, our measure of female fitness, offspring emergence, did not differ between treatments, even though life-history characters such as fertility and fecundity did. Results are discussed in terms of costs and benefits of sexual selection and sexual conflict.  相似文献   

7.
Co‐evolutionary arms races have provided clear evidence for evolutionary change, especially in host–parasite systems. The evolution of host‐specific races in the common cuckoo (Cuculus canorus), however, is also an example where sexual conflict influences the outcome. Cuckoo females benefit from better adaptation to overcome host defences, whereas cuckoo males face a trade‐off between the benefits of better adaptation to a host and the benefits of multiple mating with females from other host‐races. The outcome of this trade‐off might be genetic differentiation or prevention of it by genetic swamping. We use a simulation model to test which outcome is more likely with three sympatric cuckoo host‐races. We assume a cost for cuckoo chicks that express a host adaptation allele not suited to their foster host species and that cuckoo males that switch to another host‐race experience either a fitness benefit or cost. Over most of the parameter space, cuckoo male host‐race fidelity increases significantly with time, and gene flow between host‐races ceases within a few thousand to a hundred thousand generations. Our results hence support the idea that common cuckoo host‐races might be in the incipient stages of speciation.  相似文献   

8.
Six sister populations of Drosophila melanogaster kept under identical environmental conditions for greater than 600 generations were reciprocally crossed to investigate the incidence of population divergence in allopatry. Population crosses directly influenced fitness, mating frequency, and sperm competition patterns. Changes in both female remating rate and the outcome of male sperm competition (P1, P2) in response to foreign males were consistent with intersexual coevolution. Moreover, seven of the 30 crosses between foreign mates resulted in significant reductions in female fitness, whereas two resulted in significant increases, compared to local matings. This tendency for foreign males to reduce female fitness may be interpreted as evidence for either sexually antagonistic coevolution or the disruption of mutualistic interactions. However, instances in which female fitness improved via cohabitation with foreign males may better reveal sexual conflict, signalling release from the cost of interacting with locally adapted males. By this metric, female reproduction in D. melanogaster is strongly constrained by local adaptation by males, a situation that would promote antagonistic coevolution between the sexes. We conclude that sexual selection can promote population differentiation in allopatry and that sexual conflict is likely to have played a role in population differentiation in this study system.  相似文献   

9.
Detecting sexual conflict and sexually antagonistic coevolution   总被引:3,自引:0,他引:3  
We begin by providing an operational definition of sexual conflict that applies to both inter- and intralocus conflict. Using this definition, we examine a series of simple coevolutionary models to elucidate fruitful approaches for detecting interlocus sexual conflict and resultant sexually antagonistic coevolution. We then use published empirical examples to illustrate the utility of these approaches. Three relevant attributes emerge. First, the dynamics of sexually antagonistic coevolution may obscure the conflict itself. Second, competing models of inter-sexual coevolution may yield similar population patterns near equilibria. Third, a variety of evolutionary forces underlying competing models may be acting simultaneously near equilibria. One main conclusion is that studies of emergent patterns in extant populations (e.g. studies of population and/or female fitness) are unlikely to allow us to distinguish among competing coevolutionary models. Instead, we need more research aimed at identifying the forces of selection acting on shared traits and sexually antagonistic traits. More specifically, we need a greater number of functional studies of female traits as well as studies of the consequences of both male and female traits for female fitness. A mix of selection and manipulative studies on these is likely the most promising route.  相似文献   

10.
Chapman T 《Current biology : CB》2006,16(17):R744-R754
Sexual conflict arises from differences in the evolutionary interests of males and females and can occur over traits related to courtship, mating and fertilisation through to parental investment. Theory shows that sexual conflict can lead to sexually antagonistic coevolution (SAC), where adaptation in one sex can lead to counter-adaptation in the other. Thus, sexual conflict can lead to evolutionary change within species. In addition, SAC can--through its effects on traits related to the probability of mating and of zygote formation--potentially lead to reproductive isolation. In this review, I discuss that, although sexual conflict is ubiquitous, the actual expression of sexual conflict leading to SAC is less frequent. The balance between the benefits and costs of the manipulation of one sex by the other, and the availability of mechanisms by which conflict is expressed, determine whether actual sexual conflict is likely to occur. New insights address the relationship between sexual conflict and conflict resolution, adaptation, sexual selection and fitness. I suggest that it will be useful to examine systematically the parallels and contrasts between sexual and other evolutionary conflicts. Understanding why some traits, but not others, are subject to evolutionary change by SAC will require data on the mechanisms of the traits involved and on the relative benefits and costs of manipulation and resistance to manipulation.  相似文献   

11.
Arms races between and within species.   总被引:35,自引:0,他引:35  
An adaptation in one lineage (e.g. predators) may change the selection pressure on another lineage (e.g. prey), giving rise to a counter-adaptation. If this occurs reciprocally, an unstable runaway escalation or 'arms race' may result. We discuss various factors which might give one side an advantage in an arms race. For example, a lineage under strong selection may out-evolve a weakly selected one (' the life-dinner principle'). We then classify arms races in two independent ways. They may be symmetric or asymmetric, and they may be interspecific or intraspecific. Our example of an asymmetric interspecific arms race is that between brood parasites and their hosts. The arms race concept may help to reduce the mystery of why cuckoo hosts are so good at detecting cuckoo eggs, but so bad at detecting cuckoo nestlings. The evolutionary contest between queen and worker ants over relative parental investment is a good example of an intraspecific asymmetric arms race. Such cases raise special problems because the participants share the same gene pool. Interspecific symmetric arms races are unlikely to be important, because competitors tend to diverge rather than escalate competitive adaptations. Intraspecific symmetric arms races, exemplified by adaptations for male-male competition, may underlie Cope's Rule and even the extinction of lineages. Finally we consider ways in which arms races can end. One lineage may drive the other to extinction; one may reach an optimum, thereby preventing the other from doing so; a particularly interesting possibility, exemplified by flower-bee coevolution, is that both sides may reach a mutual local optimum; lastly, arms races may have no stable and but may cycle continuously. We do not wish necessarily to suggest that all, or even most, evolutionary change results from arms races, but we do suggest that the arms race concept may help to resolve three long-standing questions in evolutionary theory.  相似文献   

12.
Microevolutionary studies have demonstrated sexually antagonistic selection on sexual traits, and existing evidence supports a macroevolutionary pattern of sexually antagonistic coevolution. Two current questions are how antagonistic selection within-populations scales to divergence among populations, and to what extent intraspecific divergence matches species-level patterns. To address these questions, we conducted an intraspecific comparative study of sexual armaments and mating behaviors in a water strider (Gerris incognitus) in which male genitals grasp resistant females and female abdominal structures help ward off males. The degree of exaggeration of these armaments coevolves across species. We found a similar strong pattern of antagonistic coevolution among populations, suggesting that sexual conflict drives population differentiation in morphology. Furthermore, relative exaggeration in armaments was closely related to mating outcomes in a common environment. Interestingly, the effect of armaments on mating was mediated by population sexual size dimorphism. When females had a large size advantage, mating activity was low and independent of armaments, but when males had a relative size advantage, mating activity depended on which sex had relatively exaggerated armaments. Thus, a strong signal of sexually antagonistic coevolution is apparent even among populations. These results open opportunities to understand links between sexual arms races, ecological variation, and reproductive isolation.  相似文献   

13.
Identifying factors which allow the evolution and persistence of cooperative interactions between species is a fundamental issue in evolutionary ecology. Various hypotheses have been suggested which generally focus on mechanisms that allow cooperative genotypes in different species to maintain interactions over space and time. Here, we emphasise the fact that even within mutualisms (interactions with net positive fitness effects for both partners), there may still be inherent costs, such as the occasional predation by ants upon aphids. Individuals engaged in mutualisms benefit from minimising these costs as long as it is not at the expense of breaking the interspecific interaction, which offers a net positive benefit. The most common and obvious defence traits to minimise interspecific interaction costs are resistance traits, which act to reduce encounter rate between two organisms. Tolerance traits, in contrast, minimise fitness costs to the actor, but without reducing encounter rate. Given that, by definition, it is beneficial to remain in mutualistic interactions, the only viable traits to minimise costs are tolerance-based 'defence' strategies. Thus, we propose that tolerance traits are an important factor promoting stability in mutualisms. Furthermore, because resistance traits tend to propagate coevolutionary arms races between antagonists, whilst tolerance traits do not, we also suggest that tolerance-based defence strategies may be important in facilitating the transition from antagonistic interactions into mutualisms. For example, the mutualism between ants and aphids has been suggested to have evolved from parasitism. We describe how phenotypic plasticity in honeydew production may be a tolerance trait that has prevented escalation into an antagonistic arms race and instead led to mutualistic coevolution.  相似文献   

14.
We describe a graphical model of interlocus coevolution used to distinguish between the interlocus sexual conflict that leads to sexually antagonistic coevolution, and the intrinsic conflict over mating rate that is an integral part of traditional models of sexual selection. We next distinguish the 'laboratory island' approach from the study of both inbred lines and laboratory populations that are newly derived from nature, discuss why we consider it to be one of the most fitting forms of laboratory analysis to study interlocus sexual conflict, and then describe four experiments using this approach with Drosophila melanogaster. The first experiment evaluates the efficacy of the laboratory model system to study interlocus sexual conflict by comparing remating rates of females when they are, or are not, provided with a spatial refuge from persistent male courtship. The second experiment tests for a lag-load in males that is due to adaptations that have accumulated in females, which diminish male-induced harm while simultaneously interfering with a male's ability to compete in the context of sexual selection. The third and fourth experiments test for a lag-load in females owing to direct costs from their interactions with males, and for the capacity for indirect benefits to compensate for these direct costs.  相似文献   

15.
Conflicts of interest between mates can promote the evolution of male traits that reduce female fitness and that drive coevolution between the sexes. The rate of adaptation depends on the intensity of selection and its efficiency, which depends on drift and genetic variability. This leads to the largely untested prediction that coevolutionary adaptations such as those driven by sexual conflict should evolve faster in large populations. We tested this using the bruchid beetle Callosobruchus maculatus, a species where harm inflicted by males is well documented. Although most experimental evolution studies remove sexual conflict, we reintroduced it in populations in which it had been experimentally removed. Both population size and standing genetic variability were manipulated in a factorial experimental design. After 90 generations of relaxed conflict (monogamy), the reintroduction of sexual conflicts for 30 generations favored males that harmed females and females that were more resistant to the genital damage inflicted by males. Males evolved to become more harmful when population size was large rather than when initial genetic variation was enriched. Our study shows that sexual selection can create conditions in which males can benefit from harming females and that selection may tend to be more intense and effective in larger populations.  相似文献   

16.
Sexual conflict drives the coevolution of sexually antagonistic traits, such that an adaptation in one sex selects an opposing coevolutionary response from the other. Although many adaptations and counteradaptations have been identified in sexual conflict over mating interactions, few are known for sexual conflict over parental investment. Here we investigate a possible coevolutionary sequence triggered by mate desertion in the burying beetle Nicrophorus vespilloides, where males commonly leave before their offspring reach independence. Rather than suffer fitness costs as a consequence, our data suggest that females rely on the male's absence to recoup some of the costs of larval care, presumably because they are then free to feed themselves on the carcass employed for breeding. Consequently, forcing males to stay until the larvae disperse reduces components of female fitness to a greater extent than caring for young singlehandedly. Therefore we suggest that females may have co-evolved to anticipate desertion by their partners so that they now benefit from the male's absence.  相似文献   

17.
The impact of community complexity on pairwise coevolutionary dynamics is theoretically dependent on the extent to which species evolve generalised or specialised adaptations to the multiple species they interact with. Here, we show that the bacteria Pseudomonas fluorescens diversifies into defence specialists, when coevolved simultaneously with a virus and a predatory protist, as a result of fitness trade‐offs between defences against the two enemies. Strong bacteria–virus pairwise coevolution persisted, despite strong protist‐imposed selection. However, the arms race dynamic (escalation of host resistance and parasite infectivity ranges) associated with bacteria–virus coevolution broke down to a greater extent in the presence of the protist, presumably through the elevated genetic and demographic costs of increased bacteria resistance ranges. These findings suggest that strong pairwise coevolution can persist even in complex communities, when conflicting selection leads to evolutionary diversification of different defence strategies.  相似文献   

18.

Background

Sexual conflict theory predicts sexually antagonistic coevolution of reproductive traits driven by conflicting evolutionary interests of two reproducing individuals. Most studies of the evolutionary consequences of sexual conflicts have, however, to date collectively investigated only a few species. In this study we used the annual herb Collinsia heterophylla to experimentally test the existence and evolutionary consequences of a potential sexual conflict over onset of stigma receptivity.

Methodology/Principal Findings

We conducted crosses within and between four greenhouse-grown populations originating from two regions. Our experimental setup allowed us to investigate male-female interactions at three levels of geographic distances between interacting individuals. Both recipient and pollen donor identity affected onset of stigma receptivity within populations, confirming previous results that some pollen donors can induce stigma receptivity. We also found that donors were generally better at inducing stigma receptivity following pollen deposition on stigmas of recipients from another population than their own, especially within a region. On the other hand, we found that donors did worse at inducing stigma receptivity in crosses between regions. Interestingly, recipient costs in terms of lowered seed number after early fertilisation followed the same pattern: the cost was apparent only if the pollen donor belonged to the same region as the recipient.

Conclusion/Significance

Our results indicate that recipients are released from the cost of interacting with local pollen donors when crossed with donors from a more distant location, a pattern consistent with a history of sexually antagonistic coevolution within populations. Accordingly, sexual conflicts may have important evolutionary consequences also in plants.  相似文献   

19.
Evolutionary conflict between the sexes has been studied in various taxa and in various contexts. When the sexes are in conflict over mating rates, natural selection favors both males that induce higher mating rates and females that are more successful at resisting mating attempts. Such sexual conflict may result in an escalating coevolutionary arms race between males and females. In this article, we develop simple replicator-dynamics models of sexual conflict in order to investigate its evolutionary dynamics. Two specific models of the dependence of a female's fitness on her number of matings are considered: in model 1, female fitness decreases linearly with increasing number of matings and in model 2, there is an optimal number of matings that maximizes female fitness. For each of these models, we obtain the conditions for a coevolutionary process to establish costly male and female traits and examine under what circumstances polymorphism is maintained at equilibrium. Then we discuss how assumptions in previous models of sexual conflict are translated to fit to our model framework and compare our results with those of the previous studies. The simplicity of our models allows us to consider sexual conflict in various contexts within a single framework. In addition, we find that our model 2 shows more complicated evolutionary dynamics than model 1. In particular, the population exhibits bistability, where the evolutionary outcome depends on the initial state, only in model 2.  相似文献   

20.
Genital coevolution is a pervasive phenomenon as changes in one sex tend to impose fitness consequences on the other, generating sexual conflict. Sexual conflict is often thought to cause stronger selection on males due to the Darwin–Bateman's anisogamy paradigm. However, recent studies have demonstrated that female genitalia may be equally elaborated and perform diverse extra‐copulatory functions. These characteristics suggest that female genitals can also be primary targets of selection, especially where natural selection acts on female‐exclusive functions such as oviposition. Here, we test this hypothesis in a statistical phylogenetic framework across the whole beetle (Coleoptera) phylogeny, investigating whether coevolution of specific genital traits may be triggered by changes in females. We focus on traits of the proctiger, which composes part of the male terminalia and the female ovipositor. Our results present a comprehensive case of male–female genital coevolution and provide solid statistical evidence for a female‐initiated coevolutionary process where the vast majority of evolutionary transitions in males have occurred only after changes in females. We corroborate the hypothesis that female traits may change independently and elicit counter‐adaptations in males. Furthermore, by showing a consistent pattern across the phylogeny of the most diverse group of animals, our results suggest that this female‐driven dynamics may persist through long time scales.  相似文献   

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