Hemiclonal reproduction slows down the speed of Muller's ratchet in the hybridogenetic frog Rana esculenta

Rare recombination in otherwise asexually reproducing organisms is known to beneficially influence the fitness in small populations. In most of the investigated organisms, asexual and rare sexual generations with recombination follow each other sequentially. Here we present a case where clonal reproduction and rare recombination occur simultaneously in the same population. The hybridogenetic water frog Rana esculenta (E), a hybrid between R. lessonae (L) and R. ridibunda (R) produces gametes that only contain the unaltered maternal R part of their genome. New generations of R. esculenta usually arise from E x L matings. Intraspecific E x E matings produce mostly inviable offspring, but in rare cases, female R. ridibunda arise from such matings which are capable of recombination. In the absence of conspecific males, these R females have to mate with E males, which results in further R females, or with L males, which produces new E lineages. This indirect mechanism reintroduces recombination into the otherwise clonally transmitted R genomes in R. esculenta populations. In this study, we show through Monte Carlo simulations that, in most cases, it is sufficient that only between 1 % and 10 % of mixed water frog populations consist of R females to prevent or significantly reduce the fixation and accumulation of deleterious mutations.     

Choosy females and indiscriminate males: mate choice in mixed populations of sexual and hybridogenetic water frogs (Rana lessonae, Rana esculenta)

For several decades, behavioral ecologists have studied theeffects of the environment on the behavior of individuals;but only fairly recently they have started to ask the reversequestion: how do the behavioral strategies of individuals affectthe composition and dynamics of populations and communities?Although intuitively obvious, this feedback from individualto higher levels is difficult to demonstrate, except in systemswith exceptionally fast and marked responses of the populationsto the behavior of its members. Such a system exists in sperm-dependentspecies. In European water frogs, for instance, successfulreproduction of a hybrid species (R. esculenta, genotype LR)requires mating with one of its parental species (R. lessonae,genotype LL), except in the rare cases where hybrids are triploid.The sexual host LL, however, should avoid matings with the sexual parasite LR, because the resulting LR offspring willeliminate the L genome from their germ line. In this studywe investigate how this conflict is solved. Since water froghybrids come in both sexes, rather than as females only likein other sperm-dependent systems, we performed the tests withboth females and males. One individual was given a choice betweentwo individuals of the opposite sex, one an LL and the otheran LR. In both species, females showed the predicted preferencefor LL males, whereas males did not discriminate between LLand LR females. On the individual level, we interpret the sexdifference in choosiness by the lower costs from mating withthe wrong species (LR) and the higher benefits from matingwith large individuals in males than in females. In "normal"species, male preference for large (i.e. more fecund) femalesis advantageous, but in this system such a choice can resultin mating with the larger LR females. With respect to the structureand dynamics of mixed populations, we discuss that the observed female preference is consistent with the higher mating successof LL males found in nature. Hence, mate female choice is astrong candidate for a mechanism promoting coexistence of thesperm-dependent hybrid and its sexual host. This confirms predictionsfrom previous theoretical models.     

Evolutionary history of the hybridogenetic hybrid frog Rana esculenta as deduced from mtDNA analyses [published erratum appears in Mol Biol Evol 1986 Sep;3(5):463]

mtDNA of the hybridogenetic hybrid frog Rana esculenta from Switzerland, Austria, and Poland was compared to mtDNA of the parental species R. ridibunda and R. lessonae using electrophoretic analysis of restriction enzyme fragments. Two mtDNA phenotypes, with 3.4% sequence divergence, are present in R. lessonae: type C is found in Poland, and type D is found in Switzerland. Rana ridibunda from Poland has either of two mtDNA phenotypes: type A is the typical ridibunda mtDNA, and type B is a lessonae mitochondrial genome, introgressed into R. ridibunda, that differs from type C mtDNA of R. lessonae by only 0.3%. Each of the three lessonae genomes differs from A, the typical ridibunda mtDNA, by approximately 8%. All four types of mtDNA (A and B of R. ridibunda, C and D of R. lessonae) are found in R. esculenta. Of 62 R. esculenta from Poland, 58 had type C, three had type A, and one had type B mtDNA. All nine R. esculenta from Switzerland had type D mtDNA. All three R. esculenta from Austria, from a population in which males of R. esculenta are rare, had ridibunda mtDNA, two having type B and one having type A. Both field observations and studies of mating preference indicate that the primary hybridizations that produce R. esculenta are between R. ridibunda females and R. lessonae males; thereafter, R. esculenta lineages are usually maintained by matings of R. esculenta females with R. lessonae males. The presence of ridibunda mtDNA in the three R. esculenta sampled from Austria, its occasional presence in R. esculenta populations in Poland, and its absence from R. esculenta in Switzerland support both the direction of the original hybridization and the rarity of formation of new R. esculenta lineages. The preponderance of R. esculenta individuals with lessonae mtDNA in our samples from central Europe suggests that most lineages have gone through at least one mating between an R. lessonae female and an R. esculenta male. This reveals a greater reproductive role for R. esculenta males than their partial sterility and infrequent matings would suggest.      

Cryptic female choice: frogs reduce clutch size when amplexed by undesired males

In species with internal fertilization, females can 'cryptically' choose (e.g. through sperm selection) which individuals sire their offspring, even when their overt preferences for copulatory partners are overrun by male-male competition and sexual coercion. The experiment presented here reveals that control of paternity after copulation has begun is also possible in species with external fertilization. Females of the hybridogenetic Rana essonae-Rana esculenta (LL-LR) waterfrog complex adjust their clutch size in response to mate type: they release fewer eggs when amplexed by hybrid LR males who--jeopardize successful reproduction--than when amplexed by parental LL males. This reduction in the number of eggs laid can increase a female's residual reproductive value through a second mating in the same breeding season or a larger clutch size in the next year. We argue that cryptic female choice through clutch size adjustment (i) may have evolved more often than previously assumed, and (ii) can arise even where females mate only once during a reproductive period.     

Character convergence in advertisement call and mate choice in two genetically distinct water frog hybridogenetic lineages (Rana kl esculenta, Rana kl grafi)

Patterns of advertisement call were investigated in two genetically distinct water frog lineages ( Rana kl esculenta, Rana. kl grafi ), which were identified by starch gel electrophoresis – the aim being to determinate the role of vocalization in the hybridogenetic process. Both hybrids displayed major modifications from the basic structure of the Rana ridibunda call. In Rana kl grafi , the call structure tended to correspond to that of Rana perezi in most of the studied parameters (frequency, duration, number of pulses) whereas the call of Rana kl esculenta tended to resemble that of Rana lessonae . The ascendant hierarchical classification clearly revealed such a convergence toward parental species and accounted for a divergence between hybrids. Changes in call patterns might result from both the expression of the non- ridibunda genome and the sexual selective pressure through female mate choice. Only few non- ridibunda females exhibited a preference for hybrid calls which, however, allowed some hybridogenetic males to obtain successful mates. Thus, hybridogenesis induced character convergence in courtship signal with the non- ridibunda species in hybrid zones. In any case, these changes in the courtship signal favoured the particular hybridogenetic process, which constitutes a quasi-parasitism of the non- ridibunda genome.     

Mitochondrial DNA reveals formation of nonhybrid frogs by natural matings between hemiclonal hybrids.

The European water frog Rana esculenta (RL), a natural hybrid between R. ridibunda (RR) and R. lessonae (LL), reproduces by hybridogenesis: haploid gametes usually contain an intact chromosome set of R. ridibunda (R); the lessonae nuclear genome (L) is lost from the germ line. Hybridity is restored in the next generation, via fertilization by syntopic R. lessonae. Matings between two hybrids (RL x RL) usually give inviable R. ridibunda (RR) progeny. The adult R. ridibunda subpopulation of Trubeschloo, a gravel pit in northern Switzerland, consists only of females. Fragment patterns for mitochondrial DNA (mtDNA) of these R. ridibunda were identical with those of syntopic R. esculenta and of local populations of R. lessonae; they differed from the patterns in eastern European populations of R. lessonae and of R. ridibunda mtDNAs (3.7% and 9.3% estimated sequence divergence, respectively). In contrast, mtDNAs of two R. ridibunda from an introduced Swiss population with both sexes, although different (2.7% divergence) from each other, were typical R. ridibunda rather than R. lessonae mtDNAs. These data, together with unisexuality, demonstrate conclusively that the all-female R. ridibunda population at Trubeschloo originated from matings between two R. esculenta. The formation of independently reproducing R. ridibunda populations via such hybrid x hybrid matings is precluded because progeny of these matings are unisexual. Recombination in the regenerated fertile R. ridibunda females, followed by matings with R. lessonae, nevertheless provides a mechanism for meiotic reshuffling of genetic material in ridibunda haplotypes that is not typically available in hemiclonal lineages.     

Mate sampling by female barking treefrogs (Hyla gratiosa)

Despite intense interest in mate choice, relatively little isknown about how individuals sample prospective mates. Indeed,a key issue is whether females sample males or simply matewith the first male encountered. We investigated mate samplingby female barking treefrogs (Hyla gratiosa). Females choosingmates in natural choruses did not move between males but insteadmated with the first male they approached closely. Most femalesmated with the male closest to them at the start of their mate-choiceprocess, and females were more likely to mate with the closest male when the distance to other males was large. These observationsare consistent with the hypothesis that females do not samplepotential mates but instead mate with the first male they distinguishfrom the rest of the chorus. To test this initial detectionhypothesis, we conducted a playback experiment in which weoffered females a choice between two calls, one of which was detectable above the background chorus sound at the female'srelease point, and one of which became detectable only as femalesmoved toward the initially detectable call. Females did notprefer the initially detectable call, thus ruling out the initialdetection hypothesis and implicating sampling of potentialmates by females. Based on the behavior of females in natural choruses, we hypothesize that females approach the chorus, moveto locations where they are able to detect the calls of severalmales simultaneously, and choose a mate from among these malesat some distance from the males. Such simultaneous samplingmay be common in lekking and chorusing species, which havebeen the subjects of many studies of sexual selection.     

Free female mate choice in house mice affects reproductive success and offspring viability and performance

We tested a critical assumption of sexual dialectics theory (Gowaty 1997, Feminism and Evolutionary Biology, Chapman & Hall) using house mice, Mus musculus. We asked if female house mice accrue viability benefits for their offspring when they mate with males they prefer versus with males they do not prefer. Our experiment was designed to eliminate or control other mechanisms of reproductive competition besides female mate choice. After allowing females to discriminate behaviourally between two males, which were at random with respect to phenotypic variation discriminating females were paired with preferred (P) or nonpreferred (NP) males. We then tested whether females mating with males they preferred had offspring of higher viability than females mating with nonpreferred males. In pairwise comparisons, we tested for differences in offspring performance in dominance contests and in nest-building skill. At weaning, we exposed half of the pups to cold stress. We tested progeny performance and viability in the laboratory or in outdoor field enclosures. In comparison to P females, NP females produced significantly fewer litters. Sons from P matings were socially dominant to sons from NP matings. Adult offspring from P matings built better nests than those from NP matings. In field enclosures significantly fewer NP than P offspring survived to 60 days after introduction. Male and female progeny from P matings established larger home ranges and constructed better nests than progeny from NP matings. This is the first demonstration of progeny viability differences for females allowed to express mate preferences between males presented to them at random. Copyright 2000 The Association for the Study of Animal Behaviour.     

Sexual conflict and the evolution of female mate choice and male social dominance

Conflicts between the sexes over control of reproduction are thought to lead to a cost of sexual selection through the evolution of male traits that manipulate female reproductive physiology and behaviour, and female traits that resist this manipulation. Although studies have begun to document negative fitness effects of sexual conflict, studies showing the expected association between sexual conflict and the specific behavioural mechanisms of sexual selection are lacking. Here we experimentally manipulated the opportunity for sexual conflict in the cockroach. Nauphoeta cinerea and showed that, for this species, odour cues in the social environment influence the behavioural strategies and fitness of males and females during sexual selection. Females provided with the opportunity for discriminating between males but not necessarily mating with preferred males produced fewer male offspring than females mated at random. The number of female offspring produced was not affected, nor was the viability of the offspring. Experimental modification of the composition of the males' pheromone showed that the fecundity effects were caused by exposure to the pheromone component that makes males attractive to females but also makes males less likely to be dominant. Female mate choice therefore carries a demographic cost but functions to avoid male manipulation and aggression. Male-male competition appears to function to circumvent mate choice rather than directly manipulating females, as the mate choice can be cryptic. The dynamic struggle between the sexes for control of mating opportunities and outcomes in N. cinerea therefore reveals a unique role for sexual conflict in the evolution of the behavioural components of sexual selection.     

The Effect of Assortative Mating on the Coexistence of a Hybridogenetic Waterfrog and Its Sexual Host

In central Europe, the hybridogenetic waterfrog Rana esculenta, a hybrid between Rana ridibunda and Rana lessonae, lives in sympatry with one of its parental species, the poolfrog Rana lessonae. As R. esculenta has to backcross constantly with R. lessonae in order to produce viable offspring, this coexistence is obligatory for R. esculenta. Since R. esculenta has a higher primary fitness than R. lessonae, a mechanism is required that prevents the hybrid from driving the parental species, and hence itself, to extinction. Here, we present an analytical model and a computer simulation that investigate whether assortative mating can operate as a such a control mechanism. Our results show that assortative mating is very effective in regulating coexistence in such a hybrid-host system. This is particularly true when choice is affected by the proportion of the two male types in the population. Furthermore, we could show that even if the species composition in a mixed hybrid-host population may be largely influenced by differences in life-history parameters, assortative mating still plays a very important role by stabilizing coexistence. Thus, mating behavior turns out to be more important for the populations dynamics of hybridogenetic waterfrog systems than previously assumed.     

Non-hybrid offspring from matings between hemiclonal hybrid waterfrogs suggest occasional recombination between clonal genomes

The hemiclonal waterfrog Rana esculenta , a hybrid between R. ridibunda and R. lessonae , eliminates the lessonae genome from the germline and clonally transmits the ridibunda genome (hybridogenesis). Such genomes are prone to accumulate deleterious mutations, which may explain why offspring from matings between hybrids are typically inviable. Here I present field data from a population for which experimental crossings showed that some R. esculenta pairs produce viable R. ridibunda offspring. I demonstrate: (1) that R. ridibunda metamorphs are also produced and survive under natural conditions; (2) that their genotypes are consistent with combinations of clonal ridibunda genomes found in hybrids; and (3) that all R. ridibunda are female. These females possibly recombine the clonal genomes they inherited and, upon mating with syntopic R. lessonae , produce new hemiclones with novel combinations of alleles. Hence, occasional recombination between otherwise clonal ridibunda genomes seems plausible and may provide an escape from the evolutionary dead end they were proposed to be trapped in.     

Females avoid manipulative males and live longer

Abstract Female mate choice has been demonstrated in a wide variety of species and is now accepted as an important factor in sexual selection. One of the remaining questions, however, is why females prefer specific males. Do females or their offspring benefit from their choice? Or do females choose mates to minimize costs of mating? Here we show that, in the ovoviviparous cockroach Nauphoeta cinerea, where sexual selection has been well documented, females chose mates to avoid costly male manipulation. Females were partnered with preferred or nonpreferred mates, and fitness of the females measured. We found that females lived longer when they mated with preferred males. Female lifespan depended on the rate at which offspring developed from egg to parturition: slower development led to longer life. We manipulated the male pheromone and showed that the component of the pheromone blend that makes males attractive to females also delayed parturition. Thus, like other aspects of sexual conflict in this species, offspring development and thereby the mother's lifespan depended on exposure of females to specific components of the male pheromone. Males benefit from manipulating offspring development because females with accelerated parturition remained unreceptive whereas females with slower developing offspring readily remated after giving birth to their offspring. Our results suggest a hormone‐like role for the male pheromone in N. cinerea and provide the first direct evidence of mate choice to avoid male manipulation. This study shows that dominant males may not be preferred males if they are manipulating females, why multiple components with contrasting effects can exist in a sexual signal, and emphasizes the complex fitness relationships that can arise in species with sexual conflict.     

Reproduction and hybrid load in all-hybrid populations of Rana esculenta water frogs in Denmark

All-hybrid populations of the water frog, Rana esculenta, are exceptional in consisting of independently and to some extent sexually reproducing interspecific hybrids. In most of its range R. esculenta reproduces hemiclonally with one of the parental species, R. lessonae or R. ridibunda, but viable populations of diploid and triploid hybrids, in which no individuals of the parental species have been found, exist in the northern part of the range. We test the hypothesis that nonhybrids arise every year in these all-hybrid populations, but die during larval development. Microsatellite markers were used to determine the genotypes of adults and abnormal and healthy offspring in three all-hybrid populations of R. esculenta in Denmark. Of all eggs and larvae, 63% developed abnormally or died, with some being nonhybrid (genomes matching one of the parental species), many being aneuploid (with noninteger chromosome sets), a few being tetraploid, and many eggs possibly being unfertilized. The 37% surviving and apparently healthy froglets were all diploid or triploid hybrids. In all three populations, gametogenesis matched the pattern previously described for all-hybrid R. esculenta populations in which most triploid adults have two R. lessonae genomes. This pattern was surprising for the one population in which triploid adults had two R. ridibunda genomes, because here it leads to a deficiency of gametes with an R. lessonae genome and should compromise the stability of this population. We conclude that faulty gametogenesis and mating between frogs with incompatible gametes induce a significant hybrid load in all-hybrid populations of R. esculenta, and we discuss compensating advantages and potential evolutionary trajectories to reduce this hybrid load.     

斜纹夜蛾的性选择行为

【目的】为了解斜纹夜蛾Spodoptera litura Fabricius体重、日龄、交配经历及形态特征对其性选择行为的影响。【方法】本实验通过标记成虫后,采用观察记录的方法对其进行探究。【结果】斜纹夜蛾雌虫的体重对雄虫的性选择影响比较明显,体重较大雄虫优先选择体重较小的雌虫(71.43%),而体重较小雄虫喜欢选择体重较大的雌虫(72.00%)。体重较大和体重较小的雄虫都能获得体重较大雌虫的交配选择,但是体重较大者被选择的机会更大(70.00%),体重较小的雄虫不能获得体重较小雌虫的选择。雄虫仅选择1日龄的雌虫,而雌虫偏向选择3日龄和5日龄雄虫。交配经历影响斜纹夜蛾的性选择,未交配的雄虫优先选择未交配的雌虫(86.67%),但未交配的雌虫则优先选择已交配的雄虫(66.67%)。雄虫的形态特征(体长、翅展、腹长、复眼间距和触角长)对雌虫性选择有较明显的影响,但雌虫的形态特征除翅展的大小外,其体长、腹长、复眼间距和触角长等形态特征在雄虫选择进行交配中的作用不大。【结论】体重、日龄、交配经历及形态特征都能不同程度影响斜纹夜蛾的性选择行为。     

Indications for female mate choice in grey-cheeked mangabeys <Emphasis Type="Italic">Lophocebus albigena johnstoni</Emphasis> in Kibale National Park,Uganda

Female sexual strategies affect male strategies and can play an important role in shaping mating systems. We investigated female sexual behaviour within five groups of grey-cheeked mangabeys in Kibale National Park, Uganda, and tested the hypothesis that females exhibit mate choice using as indications the prevalence of (1) females soliciting matings by presenting to males and (2) females refusing to mate with approaching males. In addition, we describe how these behaviours as well as grooming and copulation calls are distributed over high-ranking, low-ranking and migrating males and discuss these patterns with regard to trade-offs that could play a roll in female mate choice in multi-male groups. Females were promiscuous and initiated almost half of the matings, with both resident and migrating males. More than half of male mating approaches were refused by peak females. Female mate choice in this species may depend on individual female preferences, oestrus phase and male tactic.     

What is driving male mate preference evolution in Jamaican field crickets?

Male mating preferences are often a neglected aspect of studies on sexual selection. Male mating preferences may evolve if they provide males with direct‐fitness benefits such as increased opportunity to fertilize more eggs or indirect‐fitness benefits such as enhanced offspring survival. We tested these ideas using Jamaican field crickets, Gryllus assimilis, previously shown to exhibit male mating preferences. We randomly mated males to either their preferred or non‐preferred potential mates and then asked whether mating treatment influenced egg oviposition or offspring viability. Preferred females were not significantly more fecund and did not produce more viable eggs or offspring than non‐preferred females. Male mate preferences were therefore inconsistent with both the direct‐ and indirect‐fitness benefits hypotheses under the conditions of our experiment. Our null results leave us with an open question about what is driving the evolution of mating preferences in male crickets. Future research should explore the whether the offspring of preferred females are more attractive, have stronger immune systems, and/or experience higher adult longevity.     

Direct fitness benefits explain mate preference,but not choice,for similarity in heterozygosity levels

Under sexual selection, mate preferences can evolve for traits advertising fitness benefits. Observed mating patterns (mate choice) are often assumed to represent preference, even though they result from the interaction between preference, sampling strategy and environmental factors. Correlating fitness with mate choice instead of preference will therefore lead to confounded conclusions about the role of preference in sexual selection. Here we show that direct fitness benefits underlie mate preferences for genetic characteristics in a unique experiment on wild great tits. In repeated mate preference tests, both sexes preferred mates that had similar heterozygosity levels to themselves, and not those with which they would optimise offspring heterozygosity. In a subsequent field experiment where we cross fostered offspring, foster parents with more similar heterozygosity levels had higher reproductive success, despite the absence of assortative mating patterns. These results support the idea that selection for preference persists despite constraints on mate choice.     

First evidences of sexual selection by mate choice in marine zooplankton

Sexual selection is potentially important in marine zooplankton, presumably the most abundant metazoans on earth, but it has never been documented. We examine the conditions for sexual selection through mate choice and describe mating preferences in relation to size in a marine zooplankter, the pelagic copepod Acartia tonsa. Males produce spermatophores at a rate (~1 day⁻¹) much lower than known female encounter rates for most of the year and the decision to mate a particular female thus implies lost future opportunities. Female egg production increases with female size, and males mating larger females therefore sire more offspring per mating event. Similarly, females encounter males more frequently than they need to mate. Large males produce larger spermatophores than small males and the offspring production of female increases with the size of the spermatophore she receives. Additionally, large spermatophores allow females to fertilize eggs for a longer period. Thus, mating with large males reduces the female’s need for frequent matings and she may sire sons that produce more offspring because size is heritable in copepods. Finally, we show that both males and females mate preferentially with large partners. This is the first demonstration of sexual selection by mate choice in a planktonic organism.     

根田鼠的熟悉性及其自然动情下的配偶选择

报道了在室内雌鼠自然动情条件下根田鼠两性个体配偶选择的3种熟悉性效应的5组实验结果,包括雌性对熟悉和陌生雄鼠、配偶和陌生雄鼠、配偶和熟悉雄鼠的择偶行为实验 , 雄性对熟悉和陌生雌鼠、配偶和陌生雌鼠的择偶行为实验。在实验前, 将1对性成熟的雌雄鼠 (非亲缘关系) 每天关养8 h 共8 d 建立熟悉性; 配对雌雄鼠至少生育1胎则为配偶关系。在 Y 形迷宫内的30 min 实验中, 两个被选择鼠分别以项链拴在横跨选择箱顶端中央的一根铁丝上, 限制它们在各自箱内活动; 而允许异性选择鼠从中立箱自由进入两个选择箱。记录选择鼠对异性被选择鼠的访问、社会探究、攻击、交配和友好行为的频次和时间。经Wilcoxon 关联样本 T 检验发现, 除交配行为不显著外, 雌性根田鼠均选择熟悉性较高的雄鼠; 而雄鼠不具这种选择性。该结果提示雌雄根田鼠的不同择偶行为也许就是反映该种婚配制度特征的直接行为过程。因此, 在择偶行为中, 雌性根田鼠表现的单配性倾向和雄鼠的多配性倾向, 只能以其婚配制度为一雄多雌制的假设来解释。我们的实验还说明在多配制田鼠中, 一雄多雌制与混交制在雌鼠择偶行为上是不同的, 而与单配制的相似或相近, 故简单地比较多配制与单配制则不能反映田鼠亚科动物婚配制度的多样性。     

Female Copulation Calls in Guinea Baboons: Evidence for Postcopulatory Female Choice?

We tested the hypothesis that primate female copulation calls are a form of postcopulatory female choice. We collected data on female sexual swellings, sexual and agonistic behavior, copulation calls and postcopulatory behavioral interactions in a multimale-multifemale captive group of Guinea baboons over a 3-mo period. Males copulated with only a few females, and females copulated with only 1 or 2 different males in the group, suggesting a harem-like mating system similar to that of hamadryas and gelada baboons. Female copulations were most likely to occur at peak sexual swellings and male copulatory success was accounted for by dominance rank and age. Variation in female tendencies to call after copulation is best explained by the copulatory success of the male with which each female copulated the most and by the number of copulating partners. The findings are consistent with predictions that calls are likely to be associated with copulation with preferred males and the risk of sperm competition. The prediction that copulation calls increased the probability of postcopulatory mate guarding is also supported. Taken together, the findings suggest that female copulation calls may play an important role in postcopulatory sexual selection and in particular in the expression of postcopulatory female choice in primate species in which females have little opportunity to choose their mates or female mate choice is costly or both.