Mate choice in the face of costly competition

Studies of mate choice commonly ignore variation in preferencesand assume that all individuals should favor the highest-qualitymate available. However, individuals may differ in their matepreferences according to their own age, experience, size, orgenotype. In the present study, we highlight another simplereason why preferences may differ: if there is costly competitionfor mates, the poorest competitors might be better off avoidingthe highest-quality partners and instead targeting low-qualitypartners, so that they minimize the costs they incur. We presenta game-theoretical model of mate choice in which males of differingquality compete for access to females and try to retain themtill the time of mating. Our model predicts that high-qualitymales, who are better competitors, have a preference for thebest females that is typically several times stronger than thatof low-quality males. Early in the competitive period, the lattermay even prefer low-quality females over high-quality females.Thus, variation in competitive ability generates variation inboth the strength and direction of preferences. Differencesin competitive ability result in assortative mating with respectto quality, which is reinforced by variation in preferences.As the time of mating draws near and there is an increased riskof ending up unpaired, all males become indifferent to the qualityof potential mates. Our findings are equally applicable to femalechoice for males, and offer a new explanation for adaptive variationin mating preferences based on differing abilities to cope withthe costs of mate choice.     

Mate Choice and Spawning Success in the Fighting Fish Betta splendens: the Importance of Body Size, Display Behavior and Nest Size

Courtship displays should be exaggerated enough to attract mates and yet tempered so as not to deter them. We tested this hypothesis in the fighting fish Betta splendens by studying courtship displays and body size and their relationships with male parental quality and female fecundity, as well as the effects of display behavior and body size on mate choice decisions and spawning success. Because of their high degree of parental investment, males are expected to be discriminating in their choice of mates. Males who displayed more frequently built larger nests, a measure of parental quality, but larger males did not. When females were paired with males with high display rates, however, the pair had fewer eggs in their nest, even when accounting for female body mass. In a mate choice test using computer‐generated male stimuli that differed only in display behavior, females showed no preferences for displaying males vs. non‐displaying males, or for males with higher display rates vs. lower display rates. In similar tests in which the computer‐generated males differed only in size, females preferred larger males, but also preferred males that differed with respect to body size (negative assortative mating). Males preferred computer‐generated females that performed courtship displays over non‐displaying females, but showed no preferences for female body size. Neither a female's body size nor her display behavior was a significant predictor of her fecundity as estimated by the number of eggs released during spawning. Thus, our results suggest that female B. splendens must balance male parental quality (nest size) with the risk of potentially disruptive or dangerous behavior during spawning, and that females may minimize these risks through negative size‐assortative mating. Female display behavior, while unrelated to fecundity in our study, may attract males because it indicates reproductive readiness or serves a species‐recognition function.     

Female extra-pair behaviour and environmental quality in the serin (Serinus serinus): a test of the 'constrained female hypothesis'

Recent behavioural and molecular studies have shown that in most monogamous bird species extra-pair copulations and fertilizations outside the pair bond occur routinely. The consequences of female extra-pair behaviour might comprise effects on important life-history traits, such as the extent of male parental care. In this study we test the assumption that, within a species, females'' options for extra-pair mating depend on female quality and the environments that females occupy. This ''constrained female hypothesis'' predicts that females in good environments or high-quality females are able to resist males'' control efforts better than females in poor environments or low-quality females. We test the idea in the socially monogamous serin. We found that the likelihood of extra-pair paternity is significantly higher in territories with high availability of food. There was a negative relationship between environmental quality (food availability) and paternity both in natural and in experimentally manipulated habitats. Male feeding rates were negatively related to food availability and positively related to paternity. These data and the additional result that in better environments all of a females'' offspring were sired by one extra-pair male provide support for Gowaty''s ''constrained female hypothesis''.     

Male courtship song frequency as an indicator of male genetic quality in an insect species,Drosophila montana.

Most theoretical models on evolution of male secondary sexual characters and female preferences for these characters suggest that the male characters evolve in response to female preferences that may themselves evolve in response to direct or indirect benefits of choice. In Drosophila montana (a species of the D. virilis group), females use male song in their mate choice, preferring males that produce songs with short sound pulses and a high carrier frequency. We demonstrate here that the females get indirect benefits from their choice: in our data the frequency of the male song correlated with the survival rate of the male''s progeny from egg to adulthood (indirect benefit for the female), but not with the fecundity of his mating partner (no direct benefit for the female). Male wing centroid asymmetry did not correlate with male wing song characters, nor with female egg production nor the fitness of her progeny, suggesting that fluctuating asymmetry in male wings does not play a major role in sexual signalling. The fact that the male song gives the female information on the male''s condition/genetic quality in D. montana suggests that in this species the evolution of female preferences for male song characters could have evolved through condition-dependent viability selection presented in some ''good genes'' models.     

Mate inspection patterns in the female beaugregory damselfish (<Emphasis Type="Italic">Stegastes leucostictus</Emphasis>)

We observed female beaugregory damselfish (Stegastes leucostictus) as they interacted with males to see whether their movements fit the predictions of different mate-search models. We established high-quality and low-quality groups with low variance in breeding site quality and a medium-quality, high-variance breeding site group and compared focal observations of female nonforaging forays in each group. Only 8% of 137 forays monitored resulted in spawning events. Eighty-nine percent of the forays were less than 240 s and were within 7 m of the focal female’s territory. Average foray times and straight-line foray distances did not differ for females traveling between males in each group. Females entered high-quality breeding sites at a higher rate than low-quality sites and round-trip distances were also greatest in high-quality groups, indicating that females were following a more convoluted path. We interpret these results to mean that (a) female beaugregories separate the tasks of mate assessment and mate choice by conducting information-gathering forays between mating events, (b) forays are energetically costly and therefore usually short in duration and overall distance traveled, (c) information collection takes approximately the same time for high-quality and low-quality mates, but (d) females will alter their foray patterns in high-quality areas to collect additional information. These data are also consistent with the hypothesis that females optimize their search by employing a tiered process of assessment during information-gathering forays, first using an adjustable threshold to accept or reject each male based on his courtship and subsequently a fixed threshold to assess the quality of each breeding site.     

Does sexual experience affect the strength of male mate choice for high‐quality females in Drosophila melanogaster?

Although females are traditionally thought of as the choosy sex, there is increasing evidence in many species that males will preferentially court or mate with certain females over others when given a choice. In the fruit fly, Drosophila melanogaster, males discriminate between potential mating partners based on a number of female traits, including species, mating history, age, and condition. Interestingly, many of these male preferences are affected by the male''s previous sexual experiences, such that males increase courtship toward types of females that they have previously mated with and decrease courtship toward types of females that have previously rejected them. D. melanogaster males also show courtship and mating preferences for larger females over smaller females, likely because larger females have higher fecundity. It is unknown, however, whether this preference shows behavioral plasticity based on the male''s sexual history as we see for other male preferences. Here, we manipulate the sexual experience of D. melanogaster males and test whether this manipulation has any effect on the strength of male mate choice for large females. We find that sexually inexperienced males have a robust courtship preference for large females that is unaffected by previous experience mating with, or being rejected by, females of differing sizes. Given that female body size is one of the most common targets of male mate choice across insect species, our experiments with D. melanogaster may provide insight into how these preferences develop and evolve.     

Should females prefer to mate with low-quality males?

We analyse a model of mate choice when males differ in reproductive quality and provide care for their offspring. Females choose males on the basis of the success they will obtain from breeding with them and a male chooses his care time on the basis of his quality so as to maximise his long-term rate of reproductive success. We use this model to establish whether high-quality males should devote a longer period of care to their broods than low-quality males and whether females obtain greater reproductive success from mating with higher quality males. We give sufficient conditions for optimal care times to decrease with increasing male quality. When care times decrease, this does not necessarily mean that high-quality males are less valuable to the female because quality may more than compensate for the lack of care. We give a necessary and sufficient condition for high-quality males to be less valuable mates, and hence for females to prefer low-quality males. Females can prefer low-quality males if offspring produced and cared for by high-quality males do well even if care is short, and do not significantly benefit from additional care, while offspring produced and cared for by low-quality males do well only if they receive a long period of care.     

Fisherian flies: benefits of female choice in a lekking sandfly

We experimentally investigated the fitness consequences of female mate choice in order to test the relative importance of three competing but non-exclusive hypotheses for the maintenance of pronounced female mating preferences on leks: that females benefit directly; that they gain indirect Fisherian benefits by producing more attractive sons; or that they benefit indirectly because preferred males possess ''good genes'' that confer increased viability on their sons and daughters. We allowed lekking female sandflies, Lutzomyia longipalpis, to choose between males of varying attractiveness to females, and monitored the consequences for their own survival and reproductive success as well as for their offspring. In contrast to the predictions of the direct-benefits model, we found no clear sire effect on the fecundity or survival of the females themselves; females mating with more attractive males did survive longer after oviposition, but never long enough to undertake a second batch of egg laying. We also found no evidence that females gained good-genes benefits in terms of enhanced offspring survival. However, we did find that generally attractive males fathered sons who were then chosen when they in turn formed leks. Although not completely precluding other benefits, our results indicate that Fisherian benefits are at least partly responsible for maintaining female choice at L. longipalpis leks. These findings indicate the importance of testing all putative benefits concurrently in exploring the maintenance of female mate choice.     

Female Mate Preferences Among Pan troglodytes schweinfurthii of Kanyawara, Kibale National Park, Uganda

Studies of reproduction among chimpanzees traditionally have focused on the mating strategies of males. However, less is known about the mating strategies of female chimpanzees and whether they demonstrate mate choice. I investigated sexual behavior and female mate preference in the chimpanzees of the Kanyawara community. To estimate mate preferences, I analyzed female proceptivity and resistance rates of 6 estrous females toward a total of 13 males as well as male solicitation and aggression rates toward females. Males solicited some females more often than others for mating and preferred them throughout estrus, not only during the periovulatory period (POP), when conception was most likely. In contrast, though females had strong mate preferences in both non-POP and POP, their mate preferences were not consistent between the 2 phases. The shift in mate preferences is evidence of a promiscuous yet tactical mating strategy to confuse paternity. Further, females were more proceptive and generally less resistant toward eschewed males in non-POP and more proceptive and less resistant toward preferred males in POP. Hence, the results indicate that females attempted to mate selectively during the fertile phase. Kanyawara female chimpanzees appear to change their mating strategies and selectivity during estrus and thus may pursue a mixed reproductive strategy. The tactic may allow females to deceive males, indicating that promiscuity among chimpanzee females may be more strategic than previously thought.     

Sexual Competition,Coercive Mating and Mate Assessment in the One‐Sided Livebearer,Jenynsia multidentata: Are They Predictive of Sexual Dimorphism?

We investigated the mechanisms of sexual selection operating on body size in the one‐sided livebearer (Jenynsia multidentata), a small fish characterized by male dwarfism. Mating in the one‐sided livebearer is coercive: males approach females from behind and try to thrust their copulatory organ at the female genital pore. Females counter males' mating attempts by either swimming away or attacking them. We tested the hypothesis that the components of sexual selection favouring small size in males (sexual coercion) were more effective than those favouring a large size (male competition and mate choice). When alone, small males had a significantly higher success in their mating attempts than large males. The proportion of successful attempts was also positively correlated with female size. When two males competed for the same female, the large male had a significant mating advantage over the small one. With a 1 : 1 sex ratio, the large‐male mating advantage vanished because each male tended to follow a different female. Large males, however, preferentially defended large females, thus compelling small males to engage with smaller, less fecund females. Males did not discriminate between gravid and non‐gravid females, but preferred mating with larger females. This preference disappeared when males were much smaller than the female, probably in relation to the risk for the male of being eaten or injured by the female. In a choice chamber, male‐deprived females that had their sperm storage depleted remained close to males and showed a preference for large individuals, a behaviour not observed in non‐deprived females. Nonetheless, when placed with males in the same aquarium, all females showed avoidance and aggression. Struggling may represent a way by which the female assesses the skill and endurance of males.     

Variation between and within the sexes in body size preferences

Although it is often assumed that males and females have mating preferences for larger individuals of the other sex, potential underlying differences between male and female preferences for body size are not commonly investigated. Here, sexual differences in body size preferences are examined in the poeciliid fish, Brachyrhaphis rhabdophora. Females preferred larger males to smaller males, but preference did not appear to be affected by female size. One population-level analysis for males did not indicate an overall preference for larger females. A closer examination, however, revealed an effect of male size on preference; larger males preferred larger females, while smaller males preferred smaller females. It appears then that females, regardless of size, share a preference for large males, but males differ in their behaviour, depending on their body size. In addition, while the degree of difference in size between paired females did not appear to affect male preference, the degree of difference in size between paired males strongly affected female preference; the greater the difference, the more strongly females preferred the larger male. Thus, intersexual selection is found to operate in both sexes, but how it operates appears to differ. Intrasexual and intersexual differences in mating behaviour may be missed when evaluating population-wide preferences. That is, there can be underlying differences in how the sexes respond and the consequences of such differences should be considered when investigating mate choice. The results are considered in terms of the evolution of mating preferences, alternative mating strategies, assortative mating, the maintenance of trait variation in a population, and current methods to evaluate mating preferences.     

Male mate choice and the potential for complex mating dynamics in the tree lizard (Urosaurus ornatus)

A growing body of literature is recognizing that males may also play a role in the mating process by behaving non‐randomly toward potential female mates during courtship. In numerous species, discrete color polymorphisms in males are inferred to represent alternative mating tactics, which often correspond with concomitant asymmetries in ecology and behavior. In terms of their mating behavior, these ecological outcomes of a color polymorphism should affect a morph's likelihood and frequency of encountering females in a population, possibly favoring the evolution of morph‐specific mating preferences. Knowledge of how male morphs contribute to a species’ overall mating dynamics will improve our understanding of how sexual selection shapes phenotypic diversity in color polymorphic systems. We conducted a mate choice experiment to evaluate the extent and morph specificity of non‐random mating preferences by male ornate tree lizards, Urosaurus ornatus. We observed the behavior of blue and yellow males in an experimental arena in response to a choice between an orange or yellow female. We found that blue males preferred yellow females over orange females, and although yellow males visited females more often than blue males overall, their attention was not morph‐specific. Given male morph differences in choosiness, and their differences in social dominance, we conclude that female throat color may be partly under sexual selection in U. ornatus. However, a lack of concordance between male and female mating preferences (drawn from an earlier study) suggests that overall mating dynamics may serve to maintain, rather than enhance, color morph differences in this species.     

Heritable variation in the timing of spermatophore removal, a mechanism of post-copulatory female choice in crickets

Female crickets can exert post-copulatory mating preferences by prematurely removing a male's spermatophore after copulation, which terminates sperm transfer. Although most models of sexual selection assume that female mating preferences are heritable, there has been little work addressing genetic variation underlying post-copulatory mate choice. We used a paternal half-sib design, in which different males were randomly assigned as mates to several females to create half-sib families, to determine the heritability of spermatophore retention time in female house crickets, Acheta domesticus. There was significant additive genetic variance in the timing of spermatophore removal by females [h(2) = 0.50 +/- 0.19 (+/- SE)], suggesting that the timing of spermatophore removal is determined, in part, by the female's own genotype independent of the quality of her mate. The relatively high heritability of spermatophore retention time may be reflective of the absence of strong selection on this trait, consistent with previous work showing no difference in the fitness of females permitted to freely remove the spermatophore of their mates and those forced to accept complete ejaculates.     

The role of model female quality in the mate choice copying behaviour of sailfin mollies

Female mate choice copying is a socially mediated mate choice behaviour, in which a male's attractiveness to females increases if he was previously chosen by another female as a mate. Although copying has been demonstrated in numerous species, little is known about the specific benefits it confers to copying females. Here we demonstrate that the mate choice behaviour of female sailfin mollies (Poecilia latipinna) is influenced by the phenotypic quality of model females with whom males are observed consorting. Test females choosing between two males of similar body length were found to significantly increase time spent with previously non-preferred males after having observed them with a relatively high-quality female. Conversely, females were found to significantly decrease time spent with previously preferred males after having observed them with a relatively low-quality female. Female mate choice copying might be maintained by selection based on the heuristic value it provides females choosing between males whose quality differences are not easily distinguishable.     

Male mating constraints affect mutual mate choice: prudent male courting and sperm-limited females

Costs of sperm production may lead to prudence in male sperm allocation and also to male mate choice. Here, we develop a life history-based mutual mate choice model that takes into account the lost-opportunity costs for males from time out in sperm recovery and lets mate competition be determined by the prevailing mate choice strategies. We assume that high mating rate may potentially lead to sperm depletion in males, and that as a result, female reproduction may be limited by the availability of sperm. Increasing variation in male quality leads, in general, to increased selective mate choice by females, and vice versa. Lower-quality males may, however, gain access to more fecund higher-quality females by lowering their courting rate, thus increasing their sperm reserves. When faced with strong male competition for mates, low-quality males become less choosy, which leads to assortative mating for quality and an increased mating rate across all males. With assortative mating, the frequency of antagonistic interactions (sexual conflict) is reduced, allowing males to lower the time spent replenishing sperm reserves in order to increase mating rate. This in turn leads to lower sperm levels at mating and therefore could lead to negative effects on female fitness via sperm limitation.     

Mating interaction of the Japanese horned beetle Trypoxylus dichotomus septentrionalis: does male-excluding behavior induce female resistance?

Female resistance to male mating is thought to have developed as a mechanism to avoid multiple matings or to allow the choice of good quality males. Detailed mating behavior of the Japanese horned beetle Trypoxylus dichotomus septentrionalis (Kono) was examined under natural conditions to clarify the function of female resistance to mating. When a male recognized the presence of a female at the same feeding spot, it immediately began to court and mount the female and attempted to insert its genitalia. During the courtship, females performed intense resistance behavior against the mating, regardless of whether the female would eventually accept males or not. In T. dichotomus septentrionalis, it was observed that female resistance to mating did not occur for reasons of precopulatory mate choice or avoidance of multiple matings; however, additional studies on postcopulatory mate choice are needed. After copulation, males usually tried to keep females away from the sap site. Because of males' excluding behavior, females were able to stay at the sap site for feeding only when they were resisting or copulating. Females that showed resistance behavior before copulation stayed at the sap site 1.56 times longer than females that did not show the resistance behavior. Female resistance behavior in T. dichotomus septentrionalis is thus considered a tactic for prolonging their feeding duration, which is reduced by male-excluding behavior after mating.     

Male age, mating status and nuptial gift quality in a bushcricket

Female mate choice occurs in many animals, and in some species females prefer older males. Because older males have demonstrated their survival ability, they may be of higher genetic quality, providing genetic benefits to the offspring of their mates. However, in species where females receive direct benefits of matings, younger males may be more likely to provide more fertile or more nutritious ejaculates, so females may discriminate against older males. Males of the bushcricket Ephippiger ephippiger (Orthoptera: Tettigoniidae) produce large spermatophores at mating (>30% of body weight, circa 10% protein content). Female E. ephippiger discriminate against the song of older males. We examined the effects of male age and mating history on male reproductive investment (spermatophore size, sperm number, nitrogen content). Males produced spermatophores with significantly fewer sperm and of lower nitrogen content on their fourth mating, despite free access to food and a 1-week interval between matings, indicating that there is a cost of mating to males. There was no indication that older virgin males produced lower-quality spermatophores. Rather, older males produced bigger spermatophores of higher nutritional value and containing more sperm. Male age and mating history seem likely to be strongly correlated in the field. We conclude that female E. ephippiger probably prefer the songs of younger males, because in the field, this preference correlates with male mating history and therefore resources provided at mating. Thus, female preference for younger males could reflect discrimination against low-quality nuptial gifts.     

MHC-disassortative mating preferences reversed by cross-fostering.

House mice (Mus musculus domesticus) avoid mating with individuals that are genetically similar at the major histocompatibility complex (MHC). Mice are able recognize MHC-similar individuals through specific odour cues. However, to mate disassortatively for MHC genes, individuals must have a referent, either themselves (self-inspection) or close kin (familial imprinting), with which to compare the MHC identity of potential mates. Although studies on MHC-dependent mating preferences often assume that individuals use self-inspection, laboratory experiments with male mice indicate that they use familial imprinting, i.e. males learn the MHC identity of their family and then avoid mating with females carrying ''familial'' MHC alleles. To determine if female mice use familial imprinting, we cross-fostered wild-derived female mouse pups into MHC-dissimilar families, and then tested if this procedure reversed their mating preferences compared with in-fostered controls. Our observations of the female''s mating behaviour in seminatural social conditions and the genetic typing of their progeny both indicated that females avoided mating with males carrying MHC genes of their foster family, supporting the familial imprinting hypothesis. We show that MHC-dependent familial imprinting potentially provides a more effective mechanism for avoiding kin matings and reducing inbreeding than self-inspection.     

Female mate choice tactics in a resource-based mating system: field tests of alternative models

Abstract In this study we test theoretical models of female mate choice tactics in natural populations of pine engravers, Ips pini (Say) (Coleoptera: Scolytidae), a species with a resource-based mating system and high search costs. We first develop distinguishing predictions for each of four models of mate choice: random, comparison tactics, and fixed and adjustable thresholds. These predictions relate to commonly collected field data that include the visiting behavior of females and the quality of accepted and rejected mates. Using these types of data, we conclude that pine engravers use an adjustable threshold mate choice tactic because females often accepted the first male encountered, rarely revisited males, visited similar numbers of males in patches of different quality, accepted higher-quality males than those they rejected even on their first encounter with a male in a patch, and had higher acceptance thresholds in high-quality patches than in low-quality patches. This adjustable threshold tactic is consistent with a one-step decision rule and is predicted to occur in species such as pine engravers in which search costs are high and females have information about patch quality before beginning a search in a patch.     

Validation of a Method for Quantifying Male Mating Preferences in the Guppy (Poecilia reticulata)

Male and female mating preferences are commonly inferred from association times spent with potential mates in a dichotomous‐choice test. However, this assessment method is rarely validated, particularly so for male mating preferences. Using the Trinidadian guppy (Poecilia reticulata), an important model species in the study of sexual selection, we tested whether a male’s mating preference for either of two stimulus females in a dichotomous‐choice test predicted his mating behaviours directed at the preferred female when he was allowed to swim freely with both females. First, we presented individual males with two females that differed in body length in a dichotomous‐choice apparatus in which the male could only use visual cues to assess the paired females. We quantified male mating preference as the duration of time a focal male spent associating with each female. Immediately following this test, the focal male was allowed to swim freely with both females, and we quantified the time he spent sexually pursuing each female and the number of courtship sigmoid displays and copulation attempts he directed at each female. On average, males did not significantly prefer either of the two stimulus females in either of the two tests; however, the magnitude of male preference for the larger female tended to increase as the size difference between the paired females increased. More importantly, there was a significant positive relationship between male association time in the dichotomous‐choice test and both the time spent sexually pursuing and the number of courtship sigmoid displays directed at the same female initially preferred in the dichotomous‐choice test. Collectively, these results confirm that association time measured in a dichotomous‐choice test is a reliable predictor of male mating preferences in the Trinidadian guppy.