Male size does not affect the strength of male mate choice for high-quality females in Drosophila melanogaster

Theory predicts that the strength of male mate choice should vary depending on male quality when higher-quality males receive greater fitness benefits from being choosy. This pattern extends to differences in male body size, with larger males often having stronger pre- and post-copulatory preferences than smaller males. We sought to determine whether large males and small males differ in the strength (or direction) of their preference for large, high-fecundity females using the fruit fly, Drosophila melanogaster. We measured male courtship preferences and mating duration to show that male body size had no impact on the strength of male mate choice; all males, regardless of their size, had equally strong preferences for large females. To understand the selective pressures shaping male mate choice in males of different sizes, we also measured the fitness benefits associated with preferring large females for both large and small males. Male body size did not affect the benefits that males received: large and small males were equally successful at mating with large females, received the same direct fitness benefits from mating with large females, and showed similar competitive fertilization success with large females. These findings provide insight into why the strength of male mate choice was not affected by male body size in this system. Our study highlights the importance of evaluating the benefits and costs of male mate choice across multiple males to predict when differences in male mate choice should occur.     

Female mate assessment and choice behavior affect the frequency of alternative male mating tactics

Explanations for the existence of alternative male mating tacticsfocus primarily on male–male competition. Mating systems,however, are composed of interactions both within and betweenthe sexes, and the role of female behavior in shaping male matingtactics should not be overlooked. By using a dynamic state variablegame model, I examine how female mate assessment and choicebehavior affect the frequency of alternative male mating tactics.When females can accurately assess the quality of males, onlymales with high quality are likely to be chosen as mates, andthus, lower-quality males gain little fitness from courtingfemales. This leads lower-quality males to switch to an alternativemating tactic that attempts to circumvent female mate choice.In contrast, if the abilities of females to accurately assessmales are constrained by assessment costs, imperfect information,or time constraints, or if the pool of available males is smaller,then lower-quality males are increasingly chosen as mates andthey less often use alternative mating tactics. Thus, femalebehavior shapes the frequency of alternative male mating tactics.A consequence of this game between the sexes is that male behavior(i.e., increased alternative mating tactics) decreases the benefitsfemales might otherwise gain from lower assessment costs, clearersignals of male quality, more time to choose a male, and moremales from which to choose a mate.     

Multiple mating and sequential mate choice in guppies: females trade up

The trade-up hypothesis outlines a behavioural strategy that females could use to maximize the genetic benefits to their offspring. The hypothesis proposes that females should be more willing to accept a mate when the new male encountered is a superior genetic source to previous mates. We provide a direct test of the trade-up hypothesis using guppies (Poecilia reticulata), and evaluate both behavioural and paternity data. Virgin female guppies were presented sequentially with two males of varying attractiveness, and their responsiveness to each male was quantified. Male attractiveness (ornamentation) was scored as the amount of orange coloration on their body. Females were generally less responsive to second-encountered males, yet responsiveness to second males was an increasing function of male ornamentation. These attractive second males also sired a greater proportion of the offspring. There was an overall tendency for last-male advantage in paternity, and this advantage was most exaggerated when the second male was more ornamented than the first. Finally, we found that our estimate of relative sperm number did not account for any significant variation in paternity. Our results suggest that female guppies may use pre-copulatory mechanisms to maximize the genetic quality of their offspring.     

Population genetic models of male and mutual mate choice

Examples of male mate choice are becoming increasingly common, even in polygynous species. We create a series of population genetic models to examine the evolutionary equilibria and dynamics resulting from male mate choice during polygyny, alone and in the context of mutual mate choice by both sexes. We find that unless males with a preference are able to increase their overall courtship output, male preference will be lost. This loss can be counteracted if males choose females not based on arbitrary traits, but based on a trait that indicates high fertility or viability. We also conclude that if male and female preferences and traits are all controlled by different loci, the male and female mate choice systems are decoupled; the presence of a male preference then has no influence on the equilibria or dynamics of female mate choice. If male and female traits are coupled by pleiotropy, it becomes possible for a male preference to be maintained, regardless of whether preferences between the sexes are pleiotropic or controlled by separate loci.     

Sequential mate choice by multiply mating smooth newts: females become more choosy

In some species, females sequentially mate with different maleswithin a single mating period, store sperm until the eggs areeventually fertilized, and gain no other resources from themales. Halliday hypothesized that, for such species, a femalecould ensure fertilization of her eggs by mating with the firstmale that she encounters; thereafter, she can maximize the qualityof her progeny by sampling further males and by mating onlywith males of higher quality than previously mated males. Thishypothesis predicts that females' choosiness will increase asthe breeding season progresses. We tested this prediction ofHalliday's hypothesis by examining mate choice by female smoothnewts (Triturus vulgaris vulgaris). Males of this species developa dorsal crest during the courtship season. Crest height variesbetween males and is potentially an indicator of male quality.Initially, female smooth newts were equally willing to matewith males with low or high crests. However, in their secondmating, females remated only with high-crested males. Theseresults support our prediction and are consistent with Halliday'shypothesis. If crest height in smooth newts is an indicatorof quality, this change in females' mate choice criterion allowsfemales both to initiate egg-laying very early in the seasonand, subsequently, to mate preferentially with higher qualitymates     

Sex roles and mutual mate choice matter during mate sampling

The roles of females and males in mating competition and mate choice have lately proven more variable, between and within species, than previously thought. In nature, mating competition occurs during mate search and is expected to be regulated by the numbers of potential mates and same-sex competitors. Here, we present the first study to test how a temporal change in sex roles affects mating competition and mate choice during mate sampling. Our model system (the marine fish Gobiusculus flavescens) is uniquely suitable because of its change in sex roles, from conventional to reversed, over the breeding season. As predicted from sex role theory, courtship was typically initiated by males and terminated by females early in the breeding season. The opposite pattern was observed late in the season, at which time several females often simultaneously courted the same male. Mate-searching females visited more males early than late in the breeding season. Our study shows that mutual mate choice and mating competition can have profound effects on female and male behavior. Future work needs to consider the dynamic nature of mating competition and mate choice if we aim to fully understand sexual selection in the wild.     

Female mate choice in a mating system dominated by male sexual coercion

In poeciliid fishes, males can gain copulation either by courtingfemales or through sexual coercion. In some species these twotactics coexist. However, in about half of the poeciliids,males do not display, females never cooperate during copulationand all matings are achieved by thrusting the intromittentorgan toward the genital pore of apparently unaware females.In one of these species, the eastern mosquitofish (Gambusiaholbrooki), the probability of insemination is influenced bythe time females are previously deprived of males, suggestingthat females exert some control over the occurrence of matingeven in a system apparently dominated by sexual coercion. Inthe present study we investigated the tendency of female mosquitofishto approach males in relation to their reproductive status and the time they were previously deprived of males. The tendencyto approach males increased in females that were previouslydeprived of males and in females that had recently given birth.When allowed to choose between males, male-deprived femalespreferred larger males and normally pigmented over melanisticmales. Females preferred groups of three males over a singlemale, whereas the preference for three males over a group ofone male and two females was only marginally significant. Collectively,these results suggest that, even when coercive mating is theonly tactic adopted by males, females may be able to influencethe outcome of these attempts, and thus exert some controlover the paternity of their offspring.     

Male mate choice in fishes

Selection generally favours male competition for females, and female mate choice of males. If, however, females vary in quality, and if males are limited in the maximum number of females with which they can mate, then selection should also favour male mate choice. We report on male mate choice in two species of fishes with different mating systems: the threespine stickleback, which has male parental care, and the coho salmon, which has female parental care. In both species, males allocated their mating effort in direct proportion to female quality.     

Female pied flycatchers trade between male quality and mating status in mate choice

According to mate choice theory, females should consider both male quality and mating status when choosing a mate. In birds, strong experimental evidence indicates that females prefer males with elaborate traits. No comparable evidence exists to determine whether females take male mating status into account or how they may trade between male quality and male mating status. We studied mate choice of female pied flycatchers (Ficedula hypoleuca) in outdoor aviaries where the effect of territory quality could be eliminated and where we could control which males were mated and which were unmated. We used male plumage colour as our measure of male quality. In the aviaries, focal females could easily compare males and assess their plumage colour and mating status, and resident females were prevented from attacking prospecting females because of separation in different compartments. The study provided evidence for a trade-off in mate choice. Females may compromise by choosing an already mated male if he is more brightly coloured and, presumably, of higher quality than available unmated males. The study did not support the idea that polygyny is based on male deception of females, but the results were consistent with the female aggression hypothesis.     

Male mate choice by the lizard Anolis carolinensis: a preference for novel females

Laboratory and field manipulations tested whether male Anolis carolinensis lizards and discriminate preference for novel females over resident females. In 16 laboratory trials, we videotaped social interactions between paired males and females during baseline session (male and resident female housed together 1-3 weeks), resident-female session (male and reintroduced resident female), and novel-female session (male and novel female with resident female removed). We examined 22 behavioural variables. Male behaviours did not differ significantly between baseline and resident-female sessions, nor did female behaviours differ significantly between baseline, resident-female and novel-female sessions. However, between resident-female and novel-female sessions, males significantly increased display rate (320%), volleys of repetitive displaying (300%) and volley length (150%), and significantly decreased the distance (375%) and number (430%) of movements travelled away from the female. We concluded that males discriminate novel females from resident females independently of female behavioural or chemical cues. In each of 18 field trials, we first videotaped baseline social interactions of the resident male and females in a naturally occurring, polygynous, breeding group. The next day, we released two novel females into the territory (so at least one female remained) and videotaped subsequent social interactions. In comparison to baseline observations, males significantly increased the proportion of time spent in female-directed activities (from 5% towards resident females to 53% towards the novel female) and the proportion of displays directed towards novel females (from 6% towards resident females to 51% towards the novel female), and significantly decreased the proportion of time spent in territorial activities (from 75% to 19%) and the proportion of displays used in territorial activities (from 94% to 44%). Data from both experiments indicate that males appear to distinguish among individual females, and use this ability to increase reproductive success by identifying and preferentially pursuing novel females over previously inseminated resident females. From the perspective of cognitive ethology, we suggest a model by which males control mating decisions within their territories. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.     

The evolution of mate choice and mating biases

We review the current status of three well-established models (direct benefits, indirect benefits and sensory drive) and one newcomer (antagonistic chase-away) of the evolution of mate choice and the biases that are expressed during choice. We highlight the differences and commonalities in the underlying genetics and evolutionary dynamics of these models. We then argue that progress in understanding the evolution of mate choice is currently hampered by spurious distinctions among models and a misguided tendency to test the processes underlying each model as mutually exclusive alternatives. Finally, we suggest potentially fruitful directions for future theoretical and empirical research.     

Male dwarf chameleons assess risk of courting large, aggressive females

Conflict between the sexes has traditionally been studied in terms of costs of mating to females and female resistance. However, courting can also be costly to males, especially when females are larger and aggressively resist copulation attempts. We examined male display intensity towards females in the Cape dwarf chameleon, Bradypodion pumilum, in which females are larger than males and very aggressive. We assessed whether aggressive female rejection imposes potential costs on males and whether males vary their display behaviour with intensity of female rejection, female size or relative size differences. Males persisted in courtship after initial female rejection in 84% of trials, and were bitten in 28% of trials. Attempted mounts were positively associated with males being bitten. Males reduced courtship with increased intensity of female rejection. Male courtship behaviour also varied with female size: males were more likely to court and approach smaller females, consistent with the hypothesis that larger females can inflict more damage. These results suggest that, in addition to assessing female willingness to mate, male dwarf chameleons may use courtship displays to assess potential costs of persistence, including costs associated with aggressive female rejection, weighed against potential reproductive pay-offs associated with forced copulation.     

Male mating success and female mate choice in the river sculpin,Cottus nozawae (Cottidae)

Synopsis Mating success of males and its correlates were investigated in a natural population of the polygynous fluvial sculpinCottus nozawae. Furthermore, the female mate preference of this species was examined experimentally under alternative conditions for mating in a stream. The mating success of individual males (the number of females with which a male mated) ranged between 0 and 8 with a mean of 2.41 in 1983 and 2.52 in 1989, in a population of which the sex ratio was about 1 : 2 in both years, skewed toward females. Mainly due to the excess of nests without egg masses and the few nests with one egg mass, the distribution of male mating success did not fit a Poisson distribution, indicating its non-randomness. Male mating success was not correlated either with the size of the nest rocks or with the male size, suggesting that these two variables are not determinants of mating success. The mate choice experiments demonstrated that females of this species more frequently chose smaller males as mates whose nests already contained eggs than large males without eggs. Additionally, an analysis of stomach contents of guarding males suggested that the parental males ate their own eggs during egg guarding (filial-cannibalism). Based on these results and on a comparison of reproductive characteristics with congeneric species, it is suggested that one of the most important determinants for female mate choice inCottus species may be whether or not parental males are filial egg cannibals.     

Male chimpanzees prefer mating with old females

Cross-cultural studies indicate that women's sexual attractiveness generally peaks before motherhood and declines with age. Cues of female youth are thought to be attractive because humans maintain long-term pair bonds, making reproductive value (i.e. future reproductive potential) particularly important to males. Menopause is believed to exaggerate this preference for youth by limiting women's future fertility. This theory predicts that in species lacking long-term pair bonds and menopause, males should not exhibit a preference for young mates. We tested this prediction by studying male preferences in our closest living relative, the chimpanzee (Pan troglodytes). We show that despite their promiscuous mating system, chimpanzee males, like humans, prefer some females over others. However, in contrast to humans, chimpanzee males prefer older, not younger, females. These data robustly discriminate patterns of male mate choice between humans and chimpanzees. Given that the human lineage evolved from a chimpanzee-like ancestor, they indicate that male preference for youth is a derived human feature, likely adapted from a tendency to form unusually long term mating bonds.     

Female mate choice across spatial scales: influence of lek and male attributes on mating success of blue-crowned manakins

Lekking males compete for females within and among leks, yet female choice is expected to work differently at each of these spatial scales. We used paternity analyses to examine how lek versus male attributes influence mate choice in the blue-crowned manakin Lepidothrix coronata. We tested the hypotheses that females prefer (i) to mate at larger leks where a larger number of potential mates can be assessed, (ii) to mate with unrelated or highly heterozygous males expected to produce high-quality offspring, (iii) to mate with males that display at higher rates, and that (iv) display honestly reflects male genetic quality. Our results show that (i) males at larger leks are not more likely to sire young, although females nesting close to small leks travel further to reach larger leks, (ii) siring males are not less related to females or more heterozygous than expected, (iii) within a lek, high-display males are more likely to sire young, and (iv) both male heterozygosity and display rate increased with lek size, and as a result display does not reliably reflect male genetic quality across leks. We suggest that female mate choice in this species is probably driven by a Fisherian process rather than adaptive genetic benefits.