Sperm Competition

Zoological Journal of the Linnean Society (2001), 133: 369–375. With 1 figure doi:10.1006/zjls.2000.0287, available online at http://www.idealibrary.com on ... Sperm size and number variation in the red flour ... LUDOVIC ARNAUD1, ERIC HAUBRUGE1 and ...

Sexual conflict between mating partners can give rise to strategies that are advantageous for one sex but harmful to the opposite sex. Usually, sperm donors develop (offensive) traits to enhance their chances in sperm competition, while sperm recipients evolve (defensive) traits that allow them to stay in control of who fathers their offspring. Here, we demonstrate that these processes are also at work in simultaneous hermaphrodites. The hermaphroditic earthworm Lumbricus terrestris uses 40 to 44 copulatory setae to pierce into its partner's skin, causing damage and injecting a substance from its setal glands. Experimental injection of the gland substance indicates that a refractory period may be induced. More importantly, removal of the copulatory setae shows that they influence the partner's sperm uptake. When the setae are present, more sperm are taken up and sperm are distributed more equally over the four spermathecae. We interpret this as a strategy that stacks the odds for the donor's sperm in fertilizing cocoons.

Introductory courses dealing with sex, gender and sexuality are usually quite biased, going as far as to deny the reality of biology. Drawing on the Catholic tradition (Aquinas), this article presents an accessible argument aimed at restoring deliberative balance in the classroom.

World Wide Web: http://www.kli.ac.at/ Editors: Rupert Riedl, Manfred Wimmer Layout: Alexander Riegler Aim and Scope: "Evolution and Cognition" is an interdisciplinary forum devoted to all aspects of research on cognition in animals and humans. The major emphasis of the journal is on evolutionary approaches to cognition, reflecting the fact that the cognitive capacities of organisms result from biological evolution. Empirical and theoretical work from both fields, evolutionary and cognitive science, is accepted, but particular attention is paid to interdisciplinary perspectives on the mutual relationship between evolutionary and cognitive processes. Submissions dealing with the significance of cognitive research for the theories of biological and sociocultural evolution are also welcome. "Evolution and Cognition" publishes both original papers and review articles.

The European bitterling Rhodeus sericeus Pallas is a freshwater fish belonging to the Acheilognathinae, a subfamily that has an unusual spawning symbiosis with freshwater mussels. Female bitterling possess long ovipositors that they use to place their eggs onto the gills of a mussel through the mussels' exhalant siphon. Males fertilize the eggs by releasing sperm into the inhalant siphon of the mussel. The embryos develop inside the mussel for approximately a month, eventually leaving the mussel as actively swimming larvae. Because they use a discrete spawning site that can be readily manipulated they have recently been used in studies to understand oviposition choice with respect to mate and spawning site quality, host-parasite coevolution, alternative male mating tactics, and linking behavioural decisions with population dynamics. The current state of knowledge of bitterling reproductive ecology is reviewed and synthesized, and future directions for research on this species are proposed.

Although alternative mating tactics are found in males of many species, little is known about tactic-specific adaptations to sperm competition and the mechanism by which fertilization success is obtained. We now report on the sperm investment patterns of males that use alternative mating tactics in bluegill sunfish (Lepomis macrochirus). Bluegill males are characterized by three alternative mating tactics: parentals, sneakers, and satellites. Parentals delay maturation and adopt a courting and guarding tactic, whereas sneakers and satellites mature precociously and, respectively, use sneaking and female mimicry to steal fertilizations from parentals. We found differences among the tactics in testes weight, sperm longevity, and ejaculate sperm density and competitiveness. Parentals had the largest testes, but the smallest relative to their body weight. Satellites had intermediate-sized testes, and sneakers had the smallest testes, but the largest relative to their body weight. Within each tactic, there was a positive relationship between testes weight and body weight, but the exact relationship differed among the tactics and could not be attributed solely to allometry. Parentals had longer-lived sperm compared with that of both sneakers and satellites. Ejaculate sperm density was greatest in sneakers, satellites were intermediate, and parentals had the lowest. Competition experiments involving equal volumes of ejaculate showed that fertilization success increased linearly with sperm number, consistent with a rafflelike process. However, independent of sperm number, parental sperm were superior at fertilizing eggs. We interpret these sperm investment patterns in relation to differences in sperm competition risk, number of mating opportunities, and alternative investment options.

At night, bats utter loud echolocation calls at high repetition rates that may reveal the location and current behaviour of callers to eavesdropping bats. Given the strong attenuation of echolocation calls, we predicted that territorial males of a harem-polygynous species ought to forage at close distance to females to survey their movements by social eavesdropping. We estimated a maximum detection distance of 38 m for echolocation calls of Saccopteryx bilineata (Temminck, 1838) (Chiroptera; Emballonuridae) broadcasted within the forest under the sound transmission conditions of our study site and for an assumed signal detection threshold of 20 dB SPL (50 m for a threshold of 0 dB SPL). We then simultaneously radio-tracked the nocturnal movements of eight male-female pairs that each rested in the same harem territory during the day and measured the distances at which dyads foraged. Male-female pairs foraged at a median distance of 139 m. In the case of 90% of simultaneous bearings, males foraged at distances that prevented eavesdropping on 44 kHz echolocation calls (>38 m; 87% of radio fixes >50 m). Males and females of the same daytime territory roosted, on average, 226 ± 194 m apart from each other at night. Thus, males were most likely unaware of where females foraged as a result of the strong attenuation of female echolocation calls. In general, such acoustic constraints on social eavesdropping may promote extra-harem group paternities, female choice, and sperm competition in bats, and may therefore present an important selective force in the evolution of bat mating systems.

Eriophyoid mites are excellent candidates for ethological research using the approaches of behavioural ecology and sociobiology. These tiny haplodiploid mites are highly specialized plant parasites, producing galls, forming nests, inhabiting refuges or living freely on plants. They reproduce via spermatophores deposited on a substrate and without pairing, which is a fascinating, though still poorly understood, mode of reproduction widespread in some groups of arthropods. Eriophyoid males can be involved in external sperm competition. In some species they also guard pre-emergent females and deposit spermatophores beside them. Although slow-walking, the minute eriophyoid mites can disperse for long distances on air currents or specific animal carriers. After landing on a plant they can distinguish between suitable and unsuitable hosts. Biological observations on a deuterogynous species indicate that parasociality could occur among eriophyoid mites. Many eriophyoids are of economic importance. Knowledge of their behaviour may promote understanding their ecology, may resolve problems in their phylogeny and may help developing methods for their control. In this paper, attention is directed to dispersal modes of eriophyoid mites, their feeding and host acceptance, spermatophore deposition and mating, defence against predators, and social behaviour.

To study the effects of Citrullus colocynthis on testicular function and fertility, 70% methanolic extract of C. colocynthis was fed orally to male albino rats at the dose levels of 75 and 150 mg/kg body wt/day for 60 days. Oral administration of C. colocynthis caused a significant decrease in testicular weight and sperm concentration. The level of serum testosterone, LH and FSH also declined and spermatogenesis was impaired. The histoarchitecture of the testes in the rats receiving C. colocynthis methanolic extract showed degenerative changes and disruption of spermatogenesis and the number of spermatogonia remained significantly decreased. Thus the antifertility effects of C. colocynthis seemed to be mediated by disturbances in structure and testicular function including leydig and Sertoli cells resulting in an alteration in physio-morphological events of spermatogenesis.

We explored aspects of men's and women's short-term sexual psychology as a function of a potential short-term partner's relationship status. A total of 209 men and 288 women reported how likely they would be to pursue a casual sexual relationship with an attractive member of the opposite sex who was (1) married, (2) not married but has casual sexual partners, or (3) not married and has no casual sexual partners. Guided by sperm competition theory, we predicted and found that men prefer short-term sex partners who are not already involved in relationships and hence present a relatively low risk of sperm competition. Because women sometimes use short-term sexual relationships to acquire long-term partners, we predicted and found that women prefer short-term sexual partners who are not already involved in relationships and hence present relatively greater promise as a potential long-term partner. Finally, across each of the three levels of the imagined partner's relationship status, men reported a greater likelihood than did women of pursuing a casual sexual relationship. Discussion addressed methodological limitations and directions for future work.

The timing of breeding may not only affect breeding patterns such as the overlap of chick rearing period with the peak in food availability but also the opportunity for extra-pair mating. A negative relationship has been predicted between extra-pair paternity and breeding synchrony, assuming that male extra-pair activity is traded against mate guarding and parenting duties. In contrast, if female ability to assess male quality is temporally constrained, sperm competition might be a positive function of breeding synchrony. Here we manipulated the progress of nesting by nest material exchange within nesting aggregations to see whether the timing of breeding affects extra-pair paternity in house sparrows. We found that late broods within nesting clusters contained extra-pair young more often than early broods, but breeding synchrony did not turn out to be a significant predictor of extra-pair paternity. Our study indicates that temporal constraints of male extra-pair activity may account for extra-pair paternity levels, but it is also possible that late-breeding females may accept extra-pair copulations to ensure egg fertilization.

Sperm competition is the competition between the sperm of two or more males to fertilize a femaleÕs egg(s). We examined how men under a high recurrent risk of sperm competition might attempt to prevent and correct their partnersÕ sexual infidelity. Three hundred and five males drawn from universities and surrounding communities rated their partnerÕs physical attractiveness and personality characteristics (to assess their recurrent risk of sperm competition), and reported their use of tactics designed to prevent partner infidelity (mate retention tactics) and their use of specific copulatory behaviors arguably designed to displace the semen of rival men (semen-displacing behaviors). As hypothesized, men at a high recurrent risk of sperm competition were more likely to use mate retention tactics and to perform semen-displacing behaviors.

Territoriality and agonistic behaviour against conspecifics and heterospecifics was recorded for nine breeding pairs of bearded vulture Gypaetus barbatus between 1992 and 1996 in the Pyrenees (NE Spain). For both sexes, the defence intensity increased from the pre-laying to the chick-rearing period. The intensity of nest defence was significantly higher in males during the pre-laying period but no sex differences were found during the incubation and chick-rearing periods. Competition for nest sites, food and the potential risk of predation may affect the bearded vulture's nest defence behaviour towards other species. Most agonistic interactions took place against Eurasian griffon vultures (the most abundant species and the most important competing for nest sites) and common ravens (the most likely potential predator and a kleptoparasitic species). Nest defence against conspecifics mainly took place during the pre-laying period and may be linked to sperm competition and food resource competition.

The evolution of alternative male mating phenotypes inevitably involves variation in risk or intensity of sperm competition. Males that typically mate in disfavoured roles (i.e. sneakers/parasitic males) are predicted to experience higher magnitudes of sperm competition than males mating in favoured roles (preferred by females/exhibiting mate monopolisation). Here, we investigated whether two distinct male phenotypes in corkwing wrasse (Symphodus melops) differ with respect to adaptations for sperm competition in terms of sperm quantity, sperm motility and fertilising capacity. We found that males exhibiting female mimicry (disfavoured role) had both absolutely and relatively larger gonads than males with typical secondary sexual characters (favoured role). Moreover, a higher proportion of sperm from female mimics was motile 5 min after activation compared to sperm of territorial males. There were, however, no differences in sperm concentration or in in vitro fertilisation ability between the two male morphs. We also examined whether the male phenotypes differed in some immune parameters and if any such variation is associated with sperm traits. Current theories predict that ejaculate quality should be negatively correlated with the level of immunocompetence. Territorial males had relatively heavier spleens than female mimics, but whether this reflects differing immunocompetence is uncertain, since the spleen is also an important organ for erythrocyte storage. Furthermore, there were no differences in the densities of circulating lymphocytes or granulocytes, and the immune parameters did not covary with the sperm traits. Differences in immunocompetence are therefore unlikely to provide a major proximate explanation for variations in sperm traits in corkwing wrasse.

"Rape of women by men might be generated either by a specialized rape adaptation or as a by-product of other psychological adaptations. Although increasing number of sexual partners is a proposed benefit of rape according to the “rape as an adaptation” and the “rape as a by-product” hypotheses, neither hypothesis addresses directly why some men rape their long-term partners, to whom they already have sexual access. In two studies we tested specific hypotheses derived from the general hypothesis that sexual coercion in the context of an intimate relationship may function as a sperm competition tactic. We hypothesized that men’s sexual coercion in the context of an intimate relationship is related positively to his partner’s perceived infidelities and that men’s sexual coercion is related positively to their mate retention behaviors (behaviors designed to prevent a partner’s infidelity). The results from Study 1 (self-reports from 246 men) and Study 2 (partner-reports from 276 women) supported the hypotheses. The Discussion section addresses limitations of this research and highlights future directions for research on sexual coercion in intimate relationships."

Over the last century, sexual selection has grown from a controversial theory into a vast field of theoretical and empirical research. Although Darwin outlined two major mechanisms within his theory, male-male competition and female mate choice, the latter has promoted a wealth of research by virtue of its complexity. Despite decades of research into how female preferences and sexually selected traits have evolved, there is still little consensus as to why females prefer the males they do. Preferences are thought to evolve from either direct selection on the preference, as females themselves benefit directly from mating with a preferred male, or through indirect selection on the preference via offspring fitness. In all cases however, female preferences should compensate for the costs of discriminating between potential mates, if they are to remain overall beneficial. The fitness benefits of mating with preferred males were investigated here using the fruitfly Drosophila simulans, employing a range of behavioural, phenotypic and quantitative genetic approaches. The findings presented here indicate that female Drosophila simulans do not gain directly from mating with a preferred male. Multiple mating can increase fecundity, although costs from male harassment can reduce the net benefit. They also indicate that females may benefit indirectly from mating with attractive males as attractiveness is heritable and sons of preferred males are themselves preferred. There is also evidence that attractive males are successful in both the pre-and post-copulatory sense, as preferred males are better sperm competitors than less-preferred males. However, although there appear to be benefits from preferred males via their sons, there appear to be no benefits from males via their daughters' fitness. These findings collectively indicate that female preferences in Drosophila simulans are driven by indirectly selected benefits (via Fisherian sons), and that females benefit directly from mating multiply.

The origins and evolution of sperm storage in Brachyura are enigmatic: sperm is either stored in seminal receptacles, accessible via the vulvae on the sixth thoracic sternite, or in spermathecae at the border between the seventh and eighth sternites. Crabs with spermathecae are collectively referred to as "podotremes" while crabs with seminal receptacles belong to the Eubrachyura. The position of gonopores is the primary basis for subdividing the Eurachyura into the Heterotremata (female vulvae + males with coxal gonopores) and Thoracotremata (female vulvae + males with sternal gonopores). We present a hypothesis about the evolution of seminal receptacles in eubrachyuran female crabs and argue that the sternal gonopore has been internalized into chitin-lined seminal receptacles and the vulva is in fact a secondary aperture. The loss of some or all of the ancestral chitinous seminal receptacle lining was linked to ventral migration of the oviduct connection. Male and female strategies are to maximize gamete fertilization. The most important variable for females is sperm supply, enhanced by long-term storage made possible by the seminal receptacle. To maximize their fertilization rates males must adapt to the structure of the seminal receptacle to ensure that their sperm are close to the oviduct entrance. The major evolutionary impetus for female mating strategies was derived from the consequences of better sperm conservation and the structure of the seminal receptacle. The advantages were all to the females because their promiscuity and sperm storage allowed them to produce more genetically variable offspring, thereby enhancing variation upon which natural selection could act. We extend our arguments to Brachyura as a whole and offer a unifying explanation of the evolution of seminal receptacles, comparing them with the spermathecae found in "Podotremata": they were independent solutions to the same problem: maintaining sperm supply during evolutionary carcinization. Explanation of eubrachyuran mating strategies requires analysis of the mating-moulting link, indeterminate vs. determinate growth format and seminal receptacle structure. Two alternatives for each of these characters means that there are eight possible outcomes. Six of these outcomes have been realized, which we term Portunoid, Majoid, Eriphoid, Xanthoid, Cancroid, and Grapsoid-Ocypodoid strategies, respectively. Mapping these characters on to a workable phylogeny (wherein some changes to the seminal receptacle + moulting-mating links are assumed to have occurred more than once) produces the following relationships: Portunoids + Majoids are a sister group to the rest of the Eubrachyura, which fall into two sister groups, Eriphoids + Xanthoids and Cancroids + Grapsoid-Ocypodoids and the "Podotremata" is sister group to all the Eubrachyura.

Males among many species, including humans, evaluate cues of sperm competition risk and adjust accordingly their sperm competition tactics. The number of potential sexual rivals can serve as an index of sperm competition risk. Therefore, men may adjust their in-pair copulatory interest in accordance with the presence of sexual rivals. Using self-reports from 45 married men, we test the hypotheses that the time a man's wife spends with other men—either male friends or male coworkers—will positively predict a man's copulatory interest in his wife (Hypothesis 1) and his anger (Hypothesis 2), upset (Hypothesis 3), and frustration (Hypothesis 4) in response to his wife's sexual rejection. The results show that the time wives spend with male friends (but not male coworkers) predicts their husbands' anger, upset, and frustration in response to sexual rejection, providing support for Hypotheses 2–4. Discussion highlights novel contributions of the current research and provides a potential explanation for the discrepant findings regarding male friends versus male coworkers.

Postcopulatory competition between males, in the form of sperm competition, is a widespread phenomenon in many animal species. The extent to which sperm competition has been an important selective pressure during human evolution remains controversial, however. The authors review critically the evidence that human males and females have psychological, behavioral, and physiological adaptations that evolved in response to selection pressures associated with sperm competition. The authors consider, using evidence from contemporary societies, whether sperm competition is likely to have been a significant adaptive problem for ancestral humans and examine the evidence suggesting that human males have physiological and psychological mechanisms that allow for "prudent" sperm allocation in response to variations in the risk of sperm competition.

Postcopulatory processes might play an important role in sexual selection. In theory, fertilization success could be controlled by females via selection of particular sperm within their reproductive tract, or it could be determined by sperm competition per se. In practice, these two mechanisms are difficult to disentangle. To assess the relative importance of both mechanisms we used artificial insemination in combination with measurements of sperm quality (swimming speed and motility) in mallards. In this species, females often lack behavioral control over copulations and hence may use postcopulatory mechanisms to optimize their reproductive output. One important factor affecting female fitness may be selection of genetically compatible males. To investigate the influence of sperm quality and parental relatedness on paternity we inseminated 12 groups of related females with a sperm mixture containing equal numbers of sperm from a brother and from an unrelated male. Paternity was independent of the relatedness of the siring male to the female but was significantly affected by long-term sperm swimming speed and motility. No interaction between relatedness and sperm quality on paternity was observed. These results suggest that female mallards are not able to select sperm on a purely genetic basis and emphasize the importance of sperm quality in gaining paternity.

Sperm competition occurs when the sperm of multiple males concurrently occupy the reproductive tract of a female and compete to fertilize an egg. We used a questionnaire to investigate psychological responses to the risk of sperm competition for 237 men in committed, sexual relationships. As predicted, a man who spends a greater (relative to a man who spends a lesser) proportion of time apart from his partner since the couple's last copulation reported (a) greater sexual interest in his partner, (b) greater distress in response to his partner's sexual rejection, and (c) greater sexual persistence in response to his partner's sexual rejection. All effects were independent of total time since the couple's last copulation and the man's relationship satisfaction. Discussion addresses limitations of the current research and situates the current results within the broader comparative literature on adaptation to sperm competition.

Sperm competition was identified in 1970 as a pervasive selective force in post-copulatory sexual selection that occurs when the ejaculates of different males compete to fertilise a given set of ova. Since then, sperm competition has been much studied both empirically and theoretically. Because sperm competition often favours large ejaculates, an important challenge has been to understand the evolution of strategies through which males invest in sperm production and economise sperm allocation to maximise reproductive success under competitive conditions. Sperm competition mechanisms vary greatly, depending on many factors including the level of sperm competition, space constraints in the sperm competition arena, male mating roles, and female influences on sperm utilisation. Consequently, theoretical models of ejaculate economics are complex and varied, often with apparently conflicting predictions. The goal of this review is to synthesise the theoretical basis of ejaculate economics under sperm competition, aiming to provide empiricists with categorised model assumptions and predictions. We show that apparent contradictions between older and newer models can often be reconciled and there is considerable consensus in the predictions generated by different models. We also discuss qualitative empirical support for some of these predictions, and detail quantitative matches between predictions and observations that exist in the yellow dung fly. We argue that ejaculate economic theory represents a powerful heuristic to explain the diversity in ejaculate traits at multiple levels: across species, across males and within individual males. Future progress requires greater understanding of sperm competition mechanisms, quantification of trade-offs between ejaculate allocation and numbers of matings gained, further knowledge of mechanisms of female sperm selection and their associated costs, further investigation of non-sperm ejaculate effects, and theoretical integration of pre-and post-copulatory episodes of sexual selection.

A comparative evolutionary psychological perspective predicts that species that recurrently faced similar adaptive problems may have evolved similar psychological mechanisms to solve these problems. Sperm competition provides an arena in which to assess the heuristic value of such a comparative evolutionary perspective. The sperm competition that results from female infidelity and polyandry presents a similar class of adaptive problems for individuals across many species. The authors first describe mechanisms of sperm competition in insects and in birds. They suggest that the adaptive problems and evolved solutions in these species provide insight into human anatomy, physiology, psychology, and behavior. The authors then review recent theoretical and empirical arguments for the existence of sperm competition in humans and discuss proposed adaptations in humans that have analogs in insects or birds. The authors conclude by highlighting the heuristic value of a comparative evolutionary psychological approach in this field.

Sexual conflict in poeciliid fishes is well-documented, particularly male sexual harassment and its effects on females. For instance, male attempts to force copulations influence female feeding, energy allocation, and preference for shoaling partners. However, there has been little research conducted to determine how the social environment shapes the occurrence and intensity of sexual harassment. In this study we ask whether an audience male influences the sexual behaviors of a focal male, the correlated feeding time reduction of female Poecilia latipinna, and if the size of the audience male (larger or smaller than the focal male) influences these behaviors. We presented a video of a male, either smaller or larger than the focal male, or an empty tank (control) to a female interacting with a male or female partner and measured feeding times and sexual behaviors. We found that male sexual behaviors increased in the presence of an audience male, especially if the audience male was larger than the focal male. Females fed more in the presence of a partner female than in the presence of a male, which was independent of the audience (i.e., video treatment). Focal female aggression towards the partner female increased with the size of the audience male. The present study shows that an audience male has multiple interacting influences on both male and female behavior. address: [email protected] (A.M. Makowicz).

Deleterious mutations can accumulate in the germline with age, decreasing the genetic quality of sperm and imposing a cost on female fitness. If these mutations also affect sperm competition ability or sperm production, then females will benefit from polyandry as it incites sperm competition and, consequently, minimizes the mutational load in the offspring. We tested this hypothesis in the guppy (Poecilia reticulata), a species characterized by polyandry and intense sperm competition, by investigating whether age affects post-copulatory male traits and sperm competition success. Females did not discriminate between old and young males in a mate choice experiment. While old males produced longer and slower sperm with larger reserves of strippable sperm, compared to young males, artificial insemination did not reveal any effect of age on sperm competition success. Altogether, these results do not support the hypothesis that polyandry evolved in response to costs associated with mating with old males in the guppy.

Because snakes have a highly simpli¢ed morphology, and many species have a wide (and broadly overlapping) range of adult body sizes within each sex, they o¡er an excellent opportunity to compare body composition of males and females. Evolutionary theory predicts that particular body components should be di¡erentially enlarged in the two sexes. For example, we might expect the reproductive success of females to be enhanced by enlargement of organ systems involved in the processing and storage of energy (e.g. alimentary tract, liver, fat stores) whereas males would bene¢t from the enlargement of systems important for mate-searching, male^male combat and sperm competition (e.g. larger mass of skeletal muscles, tail, and kidneys). Dissection of 243 specimens of three snake species (117 Vipera aspis, 43 Elaphe longissima, 83 Coluber virid£avus) broadly supported these predictions. Strong sex di¡erences were apparent in relative sizes (masses) of all the non-gonadal body components that we weighed. For example, males consistently had more musculature (relative to body length) than did conspeci¢c females. Dimorphism in relative muscle mass is likely to be one of the most fundamental and widespread morphological di¡erences between males and females in the Animal Kingdom.

There is a natural range of variation in sperm morphology inside males. This variation may be adaptive or a result of poor quality control of sperm production. Sperm aggregates can also show different morphologies inside ejaculates. Preliminary analyses in scorpions suggest the existence of a sperm package morphological variation. It is unclear if this is a true polymorphism. The main purpose of this analysis is to evaluate polymorphism in sperm packages of scorpions. Some species from the order showed width variation or spatial variation that was associated to the number of folds. Some ejaculates of Bothriurus bonariensis and Brachistosternus ferrugineus males showed width dimorphism, but may be related to the natural variation of sperm width. However, sperm packages in B. ferrugineus showed lower counts of spermatozoa and the apparition of these sperm packages seemed to increase at the beginning of the reproductive season in one of the species. A marked width dimorphism of sperm packages appeared inside ejaculates of Caraboctonus keyserlingi. The adaptive significance of sperm package differences is not well understood. Differences in width may be a consequence of sperm package production errors, resulting in sperm packages with fewer spermatozoa. Sperm package polymorphism in C. keyserlingi may be linked to sperm competition risk and may be associated to other characters and strategies. Alternative hypotheses to the pattern found are further analyzed and discussed within a sexual selection framework.

Many reproductive traits, including ejaculate characteristics, usually show remarkable seasonal variation, but the potential for such dynamics in sperm morphology has been overlooked. Several studies have revealed high within-male repeatability in sperm morphology, but samples have typically been collected within a few hours or days, and the consistency of sperm morphology over longer periods remains unexplored. Here, we tested whether ejaculate traits, including sperm morphology, sperm number, and sperm velocity, exhibit seasonal phenotypic plasticity in a long-lived seasonal breeder, the red-winged blackbird (Agelaius phoeniceus). We found absolute and/or relative flagellum length and sperm velocity to increase across the season, whereas sperm numbers within ejaculates declined. Sperm morphological traits were further positively associated with harem size or the total number of offspring that fledged in each male's territory, suggesting that sperm morphology is likely to be linked to male reproductive quality. The underlying mechanisms of these patterns of seasonal variation remain unresolved, but we discuss our results in the context of dynamics of reproductive hormones, testicular structures and function, and reproductive behavior.

Males must partition their limited reproductive investments between traits that promote access to females (sexual ornaments and weapons) and traits that enhance fertilization success, such as testes and ejaculates. Recent studies show that if the most weaponized males can monopolize access to females through contest competition, thereby reducing the risk of sperm competition, they tend to invest less in sperm production. However, how males invest in sexual ornaments relative to sperm production remains less clear. If male ornaments serve as badges of status, with high-ranking males attaining near-exclusive access to females, similar to monopolizing females through combat, their expression should also covary negatively with investment in post-mating traits. In a comparative study across primates, which exhibit considerable diversification in sexual ornamentation, male weaponry and testes size, we found relative testes size to decrease with sexual ornaments but increase with canine size. These contrasting evolutionary trajectories might be driven by differential selection, functional constraints or temporal patterns of metabolic investment between the different types of sexual traits. Importantly , however, our results indicate that the theory of relative investments between weapons and testes in the context of monopolizing females can extend to male ornaments.

After mating, females may experience a decline in sexual receptivity and attractiveness that may be associated with changes in the production and emission of sex pheromones. In some cases, these changes are produced by chemical substances or structures (e.g., mating plugs) produced by males as a strategy to avoid or reduce sperm competition. In scorpions, sex pheromones may be involved in finding potential mates and starting courtship. Here, we tested the hypothesis that the males of Urophonius brachycentrus, a species that produces a mating plug, use chemical communication (sex pheromones) to detect, localize, and discriminate females according to their mating status (virgin or inseminated), aided by chemical signaling. We also explored the effect of extracting of the mating plug on chemical communication and mating acceptance. We used Y‐maze olfactometers with different stimuli to analyze male choice and exploration time. To evaluate mating acceptance, we measured the attractiveness and receptivity of females of different mating status. We found that chemical communication occurs through volatile pheromones, but not contact pheromones. Males equally preferred sites with virgin or inseminated females with removed mating plug. In turn, females with these mating statuses were more attractive and receptive for males than inseminated females. This study suggests that the mating plug significantly affects female chemical attractiveness with an effect on volatile pheromones and decreasing sexual mating acceptance of females. The decline in the female's sexual receptivity is a complex process that may respond to several non‐exclusive mechanisms imposed by males and strategically modulated by females.

The annual life cycle of pond breeding amphibians is characterized by periodical migrations between three critical habitats: breeding, post breeding -feeding -and hibernating. The breeding season starts with the migration of the reproductive adults toward the breeding site and is characterized by intense manifestations in behavior and development of secondary sexual characters. Time spent in the water is strongly influenced by the outcome of success in courtship, insemination and/or fertilization. The aim of this review is to summarize some major findings of the main research directions regarding the reproductive dynamics of temperate (and especially European) amphibians. These are presented in detail for the most studied European species: Triturus vulgaris, Bufo bufo, B. calamita and Rana temporaria.

Female copulation behaviour in the black grouse, Tetrao tetrix, was studied by detailed observations of individually marked birds together with DNA fingerprinting analyses for paternity assessment. For each breeding occasion females typically mated only once with one male, and did not mate outside the lek arena. They re-mated with the same or another male usually only if the initial copulation was disturbed and was probably unsuccessful in sperm transfer. The willingness of females to copulate only once with one male suggests that multiple mating with several males incurs a cost that more than outweighs any possible fertility or sperm competition benefits. Attempts by neighbouring males to disturb copulations were frequent, but only a small fraction of these were successful in terms of causing the female to re-mate. There was no tendency for females to redirect matings to the males that had disturbed them which also suggests that disturbance risk is not limiting female choice. However, risk of disturbance does increase the cost of female choice, and in that sense it will have some impact on mating decisions, in particular if the benefits of increasing choosiness are not great.

Field observation and laboratory experiments were conducted to investigate sperm competition and patterns of sperm fertilization under different experimental conditions in the carrion ball-roller beetle Canthon cyanellus cyanellus. Males in nature can mate with females whose spermathecae contains fertile sperm from other males. Sperm precedence was investigated using a visible genetic marker. The progeny of red (homozygous recessive) virgin females mated once with a red male and afterward, once with a green beetle (homozygous dominant) and vice versa, revealed that regardless of its color, the last male to mate fertilized c.a. 50% of the eggs, suggesting strong sperm competition. Males were able to achieve higher levels of paternity (more than 80%) when mated ad libitum with previously mated females, although large amount of variance in paternity does not exclude the possibility of first male sperm precedence or female cryptic choice. These results suggest that repeated mating and sperm replacement are the mechanisms by which last males achieve sperm precedence.

The traditional narrow focus on male mate competition in studies of mammalian mating strategies has been successful in explaining many conspicuous outcomes of sexual selection. However, focusing on ungulates, I here review increasing evidence that a comprehensive understanding of sexually selected adaptations requires consideration of a broader range of sex roles, particularly those relating to female behaviour. I show how mate competition and mate choice in both sexes can interact and often lead to intra-and intersexual conflicts and sometimes also cooperation. By causing phenotypic selection, these behavioural interactions can shape evolution although the outcome depends on genetic constraints. I conclude that to advance the understanding of mammalian mating systems we must broaden our conceptual framework from being largely focused on male competitive strategies to encompass coevolutionary dynamics between the mating strategies of both sexes. Future challenges include clarifying (1) the ecological basis for the inter-and intraspecific diversity in sex roles, (2) the condition-dependence of female mating strategies, and (3) the ultimate causes of mate competition and promiscuity in females.