Euclidean distances discriminatively predict short-term and long-term attraction to potential mates

We tested the ability of a Euclidean algorithm to predict attraction to potential mates—a relatively upstream domain in the temporal sequence of the mating process. Participants in two studies reported their ideal mate preferences using a 23-item preference instrument. Separately, they rated their attraction to profiles of potential mates that varied on those 23 dimensions. Study 1 (N = 522) found that Euclidean distances predicted attraction to potential mates both in terms of (1) overall mate value and (2) unique mate value. Study 2 (N = 411) replicated these effects and further found that Euclidean mate values discriminatively predict between short- and long-term attraction. Across both studies, a Euclidean model outperformed a variety of alternative models for predicting attraction to potential mates. These results suggest that a Euclidean algorithm is a good model for how multiple preferences are integrated in mate choice.     

Sexual selection and its evolutionary consequences in female animals

For sexual selection to act on a given sex, there must exist variation in the reproductive success of that sex as a result of differential access to mates or fertilisations. The mechanisms and consequences of sexual selection acting on male animals are well documented, but research on sexual selection acting on females has only recently received attention. Controversy still exists over whether sexual selection acts on females in the traditional sense, and over whether to modify the existing definition of sexual selection (to include resource competition) or to invoke alternative mechanisms (usually social selection) to explain selection acting on females in connection with reproduction. However, substantial evidence exists of females bearing characters or exhibiting behaviours that result in differential reproductive success that are analogous to those attributed to sexual selection in males. Here we summarise the literature and provide substantial evidence of female intrasexual competition for access to mates, female intersexual signalling to potential mates, and postcopulatory mechanisms such as competition between eggs for access to sperm and cryptic male allocation. Our review makes clear that sexual selection acts on females and males in similar ways but sometimes to differing extents: the ceiling for the elaboration of costly traits may be lower in females than in males. We predict that current and future research on female sexual selection will provide increasing support for the parsimony and utility of the existing definition of sexual selection.     

Intrasexual competition in females: evidence for sexual selection?

In spite of recent interest in sexual selection in females, debate exists over whether traits that influence female-female competition are sexually selected. This review uses female-female aggressive behavior as a model behavioral trait for understanding the evolutionary mechanisms promoting intrasexual competition, focusing especially on sexual selection. I employ a broad definition of sexual selection, whereby traits that influence competition for mates are sexually selected, whereas those that directly influence fecundity or offspring survival are naturally selected. Drawing examples from across animal taxa, including humans, I examine 4 predictions about female intrasexual competition based on the abundance of resources, the availability of males, and the direct or indirect benefits those males provide. These patterns reveal a key sex difference in sexual selection: Although females may compete for the number of mates, they appear to compete more so for access to high-quality mates that provide direct and indirect (genetic) benefits. As is the case in males, intrasexual selection in females also includes competition for essential resources required for access to mates. If mate quality affects the magnitude of mating success, then restricting sexual selection to competition for quantity of mates may ignore important components of fitness in females and underestimate the role of sexual selection in shaping female phenotype. In the future, understanding sex differences in sexual selection will require further exploration of the extent of mutual intrasexual competition and the incorporation of quality of mating success into the study of sexual selection in both sexes.     

From vigilance to violence: Tactics of mate retention in American undergraduates

Although the attraction and selection of mates are central to human reproduction, the retention of acquired mates is often necessary to actualize the promise of reproductive effort. Three empirical studies used act frequency methods to identify, assess the reported performance frequencies of, and evaluate the perceived effectiveness of 19 tactics and 104 acts of human mate guarding and retention. In Study 1 (N = 105), a hierarchical taxonomy of tactics was developed from a pool of nominated acts. We then assessed the reported performance frequencies of 19 retention tactics and 104 acts and tested three hypotheses derived from evolutionary models in an undergraduate sample (N = 102). Study 2 (N = 46) provided an independent test of these hypotheses by assessing the perceived effectiveness of each tactic. Discussion draws implications for sexual poaching, susceptibility to pair-bond defection, and the power of act frequency methods for preserving the proximate specificity and systemic complexity inherent in human mating processes.     

Female-biased dispersal under conditions of low male mating competition in a polygynous mammal

Sex-biased dispersal is a common phenomenon in birds and mammals. Competition for mates has been argued to be an important selective pressure favouring dispersal. Sexual differences in the level of intrasexual competition may produce asymmetries in the costs-benefits balance of dispersal and philopatry for males and females, which may favour male-biased dispersal in polygynous species such as most mammals. This being the case, condition-dependent dispersal predicts that male-bias should decrease if mating competition relaxes. We test this expectation for red deer, where male-biased dispersal is the norm. In southwestern Spain, red deer populations located in nonfenced hunting estates presented altered structures with sex ratio strongly biased to females and high proportion of young males. As a consequence, mate competition in these populations was lower than in other, most typical red deer populations. We found that, under such conditions of altered population structure, dispersal was female-biased rather than male-biased. Additionally, mate competition positively related to male dispersal but negatively to female dispersal. Other factors such as resource competition, age of individuals and sex ratio were not related to male or female dispersal. Males may not disperse if intrasexual competition is low and then females may disperse as a response to male philopatry. We propose hypotheses related to female mate choice to explain female dispersal under male philopatry. The shift of the sex-biased dispersal pattern along the gradient of mate competition highlights its condition-dependence as well as the interaction between male and female dispersal in the evolution of sex-biased dispersal.     

动物的性选择

有性生殖为个体之间设置了一个冲突和竞争的环境,因为雌雄个体都希望最大限度地把自己的基因传递给后代。性选择保证了动物的繁殖成功。性选择可以分为性别内选择和性别间选择。性别内选择促使动物格斗器官或其他有利于在格斗中获胜的一些特征得到发展;性别间选择促使用来吸引异性的一些特征得到发展。雌性动物的配偶选择或与所选择的特征协同进化,或可以从选择中得到直接的利益。     

Gossip as an intrasexual competition strategy: Predicting information sharing from potential mate versus competitor mating strategies

We propose that one function of competitive information sharing is success in intrasexual competition. We posit that the decision to share potentially damaging information about a competitor is sensitive to the probability of that information diminishing a competitor's mate value. According to Sexual Strategies Theory (Buss & Schmitt, 1993), men and women have evolved different psychological mechanisms underlying short-term and long-term mating strategies, and display somewhat different (although partially overlapping) preferences for long-term and short-term mate choice. In two experiments, we utilized a 2?×?2 factorial within-subjects design to manipulate a potential mate's mating strategy (long-term vs. short-term) and characteristics of a rival indicative of the rival's mating strategy (long-term vs. short-term). We predicted that participants would be more likely to share information about a competitor when that information mismatched the potential mate's preferences, thereby decreasing the perceived mate value of the competitor. Using Linear Mixed Effects Modeling, Study 1 found that men and women reported that they would be more likely to share that a competitor was promiscuous when the potential mate was interested in a long-term mate than when the potential mate was interested in a short-term mate. Study 2 demonstrated similar findings for ratings of effectiveness of sharing the information. Taken together, the two studies support the central hypothesis about the role of negative information sharing in intrasexual competition and the context-specificity of its deployment depending on mating strategy pursued.     

PERSPECTIVE: INDIRECT MATE CHOICE,COMPETITION FOR MATES,AND COEVOLUTION OF THE SEXES

When Darwin first proposed the possibility of sexual selection, he identified two mechanisms, male competition for mates and female choice of mates. Extending this classification, we distinguish two forms of mate choice, direct and indirect. This distinction clarifies the relationship between Darwin's two mechanisms and, furthermore, indicates that the potential scope for sexual selection is much wider than thus far realized. Direct mate choice, the focus of most research on sexual selection in recent decades, requires discrimination between attributes of individuals of the opposite sex. Indirect mate choice includes all other behavior or morphology that restricts an individual's set of potential mates. Possibilities for indirect mate choice include advertisement of fertility or copulation, evasive behavior, aggregation or synchronization with other individuals of the same sex, and preferences for mating in particular locations. In each of these cases, indirect mate choice sets the conditions for competition among individuals of the opposite sex and increases the chances of mating with a successful competitor. Like direct mate choice, indirect mate choice produces assortative mating. As a consequence, the genetic correlation between alleles affecting indirect choice and those affecting success in competition for mates can produce self-accelerating evolution of these complementary features of the sexes. The broad possibilities for indirect mate choice indicate that sexual selection has more pervasive influences on the coevolution of male and female characteristics than previously realized.     

Lonely hearts or sex in the city? Density-dependent effects in mating systems

Two very basic ideas in sexual selection are heavily influenced by numbers of potential mates: the evolution of anisogamy, leading to sex role differentiation, and the frequency dependence of reproductive success that tends to equalize primary sex ratios. However, being explicit about the numbers of potential mates is not typical to most evolutionary theory of sexual selection. Here, we argue that this may prevent us from finding the appropriate ecological equilibria that determine the evolutionary endpoints of selection. We review both theoretical and empirical advances on how population density may influence aspects of mating systems such as intrasexual competition, female choice or resistance, and parental care. Density can have strong effects on selective pressures, whether or not there is phenotypic plasticity in individual strategies with respect to density. Mating skew may either increase or decrease with density, which may be aided or counteracted by changes in female behaviour. Switchpoints between alternative mating strategies can be density dependent, and mate encounter rates may influence mate choice (including mutual mate choice), multiple mating, female resistance to male mating attempts, mate searching, mate guarding, parental care, and the probability of divorce. Considering density-dependent selection may be essential for understanding how populations can persist at all despite sexual conflict, but simple models seem to fail to predict the diversity of observed responses in nature. This highlights the importance of considering the interaction between mating systems and population dynamics, and we strongly encourage further work in this area.     

Operational sex ratio in newts: field responses and characterization of a constituent chemical cue

Operational sex ratio (OSR) has been traditionally thought ofas a force imposing competition for mates rather than also acue used to regulate the intrasexual competition individualsencounter. To assess whether eastern red-spotted newts, Notophthalmusviridescens, could appropriately compare OSRs, we quantifiedfield responses to traps containing four males, a sexually receptivefemale, four males plus a female, or nothing as a control. Earlyin the breeding season, males from two populations chose competitivemating opportunities over no mating opportunity at all, butgenerally preferred less competitive mating prospects. Laterin the breeding season, as the OSR of newt populations becomesmore male biased, males accordingly increased their acceptanceof intrasexual competition. Females avoided groups of four males,and for both sexes, avoidance of male-biased courting groupsincreased their probability of amplexus courtship. We then isolatedan approximately 33-kD protein from male cloacal glands thatwas used by males to compare OSRs. To our knowledge, this proteinrepresents the first isolated and characterized component ofan olfactory cue used to evaluate OSR. These results supporttwo important principles regarding mating systems: (1) OSR cansomewhat paradoxically be both the source imposing competitionfor mates and the source used to reduce it, and (2) analogousto the sex in short supply often being "choosy" selecting mates,the sex in excess (here, males) appears to be choosy about itsacceptance of intrasexual competition.     

Male‐Biased Mate Competition in King Penguin Trio Parades

Darwin devised sexual selection theory to explain sexual dimorphisms. Further developments of the theory identified the operational sex‐ratio (OSR) as one of its cornerstones, and it was commonly admitted that an OSR biased toward one sex would lead to stronger selection pressures toward that sex. Recent theoretical developments have challenged this view and showed that the OSR alone does not determine the direction of sexual selection, more particularly in mutually ornamented species exhibiting high and similar parental investment by both sexes. These developments, however, focused on mutual intersexual selection, and little is known about intrasexual selection of both males and females in species exhibiting such characteristics. The first aim of our study was to test the relative involvement of males and females in same‐sex contest over mates in the king penguin, a species exhibiting mutual ornamentation of the sexes, high parental investment by both sexes, and a male‐biased OSR. We investigated the sex composition of trio parades, which are groups of three individuals that compete for mates during pair formation. We found that these trios consist of a female trailed by two fighting males in 19 of 20 cases; the 20th trio was all male. The second aim of our study was to investigate the existence of within‐sex differences in colour ornaments between individuals involved in such trios and individuals already paired. While limited sample sizes precluded detection of statistically significant differences between trios vs. pairs, reflectance measurements suggested that the beak spot of males in trios were more strongly ultraviolet than the beak spot of males in pairs. We concluded that intrasexual selection in our colony follows the typical pattern of mate competition observed in species in which sexual dimorphisms and OSR are male biased, and discussed the ultraviolet difference within the framework of the king penguins' colour perception.     

Patterns of deception in intersexual and intrasexual mating strategies

The act frequency approach (Buss 1988) was used to develop a taxonomy of deceptive mating acts and tactics and to investigate hypothesized sex differences in the use of these acts and tactics. The results indicate that males show differences in the types of deceptive acts and tactics used in intersexual versus intrasexual contexts. Intrasexually, males more frequently engage in deceptive acts and tactics related to the exaggeration of superiority and exaggeration of sexual promiscuity, intensity, and popularity. More frequent deceptive intersexual acts and tactics for males include feigned commitment, feigned sincerity, and feigned resource acquisition ability. Females more frequently engage in deceptive acts and tactics related to appearance alteration in both intersexual and intrasexual contexts. It was also found that males use deceptive intrasexual acts and tactics more frequently than females. These findings suggest that the dimensions of deception characteristic of male reproductive strategies are congruent with female mate selection criteria and the dimensions of deception characteristic of female reproductive strategies are congruent with male mate selection criteria. Results are interpreted in terms of current evolutionary psychological approaches to the understanding of sex differences in human mating strategies and the role of deception in intepersonal interaction.     

The effect of size and sex ratio experiences on reproductive competition in Nicrophorus vespilloides burying beetles in the wild

Male parents face a choice: should they invest more in caring for offspring or in attempting to mate with other females? The most profitable course depends on the intensity of competition for mates, which is likely to vary with the population sex ratio. However, the balance of pay‐offs may vary among individual males depending on their competitive prowess or attractiveness. We tested the prediction that sex ratio and size of the resource holding male provide cues regarding the level of mating competition prior to breeding and therefore influence the duration of a male's biparental caring in association with a female. Male burying beetles, Nicrophorus vespilloides were reared, post‐eclosion, in groups that differed in sex ratio. Experimental males were subsequently translocated to the wild, provided with a breeding resource (carcass) and filmed. We found no evidence that sex ratio cues prior to breeding affected future parental care behaviour but males that experienced male‐biased sex ratios took longer to attract wild mating partners. Smaller males attracted a higher proportion of females than did larger males, securing significantly more monogamous breeding associations as a result. Smaller males thus avoided competitive male–male encounters more often than larger males. This has potential benefits for their female partners who avoid both intrasexual competition and direct costs of higher mating frequency associated with competing males.     

A sex difference in the context-sensitivity of dominance perceptions

Although dominance perceptions are thought to be important for effective social interaction, their primary function is unclear. One possibility is that they simply function to identify individuals who are capable of inflicting substantial physical harm, so that the perceiver can respond to them in ways that maximize their own physical safety. Another possibility is that they are more specialized, functioning primarily to facilitate effective direct (i.e., violent) intrasexual competition for mates, particularly among men. Here we used a priming paradigm to investigate these two possibilities. Facial cues of dominance were more salient to women after they had been primed with images of angry men, a manipulation known to activate particularly strong self-protection motivations, than after they had been primed with images of angry women or smiling individuals of either sex. By contrast, dominance cues were more salient to men after they had been primed with images of women than when they had been primed with images of men (regardless of the emotional expressions displayed), a manipulation previously shown to alter men's impressions of the sex ratio of the local population. Thus, men's dominance perceptions appear to be specialized for effective direct competition for mates, while women's dominance perceptions may function to maximize their physical safety more generally. Together, our results suggest that men's and women's dominance perceptions show different patterns of context-sensitivity and, potentially, shed new light on the routes through which violence and intrasexual competition have shaped dominance perceptions.     

A few good men: Evolutionary psychology and female adolescent aggression

Criminologists have drawn attention to the fact that crime peaks in the teens and early 20s and that this pattern shows invariance over culture, history, offense, and sex. Wilson and Daly (1985) have proposed that among young, disadvantaged males, the age-crime curve reflects risky tactics aimed at averting “reproductive death.” Though young women's rate of involvement in violent crime is much lower than men's, they also show a similar age-violence curve for assault. This paper proposes that this may be the result of aggressive mate selection among young women and that, under certain specified circumstances, women may engage in low-key intrasexual strategies in addition to epigamic strategies. This paper reviews material on sex differences in violent crime and in mate selection strategies, and offers predictions about the likely circumstances under which females will use intrasexual strategies. The scant available data on female adolescent fighting suggest that female-female assaults are more common than official statistical estimates and that they are frequently triggered by three key issues related to reproductive fitness: management of sexual reputation, competition over access to resource-rich young men, and protecting heterosexual relationships from takeover by rival women.     

A conceptual review of mate choice: stochastic demography,within‐sex phenotypic plasticity,and individual flexibility

Mate choice hypotheses usually focus on trait variation of chosen individuals. Recently, mate choice studies have increasingly attended to the environmental circumstances affecting variation in choosers' behavior and choosers' traits. We reviewed the literature on phenotypic plasticity in mate choice with the goal of exploring whether phenotypic plasticity can be interpreted as individual flexibility in the context of the switch point theorem, SPT (Gowaty and Hubbell 2009 ). We found >3000 studies; 198 were empirical studies of within‐sex phenotypic plasticity, and sixteen showed no evidence of mate choice plasticity. Most studies reported changes from choosy to indiscriminate behavior of subjects. Investigators attributed changes to one or more causes including operational sex ratio, adult sex ratio, potential reproductive rate, predation risk, disease risk, chooser's mating experience, chooser's age, chooser's condition, or chooser's resources. The studies together indicate that “choosiness” of potential mates is environmentally and socially labile, that is, induced – not fixed – in “the choosy sex” with results consistent with choosers' intrinsic characteristics or their ecological circumstances mattering more to mate choice than the traits of potential mates. We show that plasticity‐associated variables factor into the simpler SPT variables. We propose that it is time to complete the move from questions about within‐sex plasticity in the choosy sex to between‐ and within‐individual flexibility in reproductive decision‐making of both sexes simultaneously. Currently, unanswered empirical questions are about the force of alternative constraints and opportunities as inducers of individual flexibility in reproductive decision‐making, and the ecological, social, and developmental sources of similarities and differences between individuals. To make progress, we need studies (1) of simultaneous and symmetric attention to individual mate preferences and subsequent behavior in both sexes, (2) controlled for within‐individual variation in choice behavior as demography changes, and which (3) report effects on fitness from movement of individual's switch points.     

Scent marking strategies of New World primates

This paper reviews recent findings on scent-marking behavior in wild New World primates. These findings are used to examine three functional hypotheses: territoriality, regulation of social and reproductive dominance, and mating competition/mate attraction. Available data provide little evidence for a territorial function of scent-marking behavior in New World primates. Evidence for a function in the regulation of social and reproductive dominance is ambiguous. The patterns of scent marking found so far (i.e., rates of scent marking according to sex and social or reproductive status, and the spatial distribution of scent marks), and the sparse information on responses to scent marks are consistent with a hypothesized function in intrasexual competition and intersexual mate choice. Suggestions for future research are made.     

Sexual selection according to Darwin: A response to Padian and Horner's interpretation

The interpretation of exaggerated structures in the vertebrate fossil record has been hampered by disagreement over the definition of sexual selection and how it relates to sexual dimorphism. Previous assertions that Darwin placed a requirement of sexual dimorphism on sexual selection are mistaken. Instead, Darwin describes variation within one sex and the exertion of a struggle (expressed as intrasexual competition, intersexual mate choice, or both) as the necessary components of sexual selection. The use of structures by one sex to attract mates or repel rivals for mates occurs independently of any existing sexual differences. Differential mating success is also a requirement of Darwinian sexual selection. Mutual sexual selection is a legitimate concept that was described by Darwin. Sexual selection remains a viable explanatory hypothesis for the presence of exaggerated structures of extinct organisms and need not be dismissed summarily, but should not be employed without support as a default hypothesis.     

Male and Female Mate-Choice Decisions by Evarcha culicivora, An East African Jumping Spider

There has been a considerable recent interest in the criteria by which animals choose mates and in the extent to which mating systems tend to be based on mutual mate choice. In this study, we consider Evarcha culicivora, a salticid spider from East Africa. This species has some unusual characteristics, including active display by females as well as males, males that kill females more frequently than females kill males and wide intrasexual variation in body size. For females, larger males are especially dangerous. Here, we demonstrate, using two experimental designs (live‐mate choice and mount choice), that virgin males, virgin females and previously mated males prefer larger opposite‐sex individuals as potential mates, but mated females prefer smaller, safer males as potential mates.     

Sex difference in travel is concentrated in adolescence and tracks reproductive interests

Sexual selection theory suggests that the sex with a higher potential reproductive rate will compete more strongly for access to mates. Stronger intra-sexual competition for mates may explain why males travel more extensively than females in many terrestrial vertebrates. A male-bias in lifetime distance travelled is a purported human universal, although this claim is based primarily on anecdotes. Following sexual maturity, motivation to travel outside the natal territory may vary over the life course for both sexes. Here, we test whether travel behaviour among Tsimane forager–horticulturalists is associated with shifting reproductive priorities across the lifespan. Using structured interviews, we find that sex differences in travel peak during adolescence when men and women are most intensively searching for mates. Among married adults, we find that greater offspring dependency load is associated with reduced travel among women, but not men. Married men are more likely to travel alone than women, but only to the nearest market town and not to other Tsimane villages. We conclude that men''s and women''s travel behaviour reflects differential gains from mate search and parenting across the life course.