Female sand gobies gain direct benefits by choosing males with eggs in their nests

In some fish species with paternal care, females prefer to spawn with males whose nests already contain eggs. Several hypotheses have been put forward to explain this behaviour, such as reduced risk of predation or cannibalism (the dilution effect), increased parental investment, and mate copying. This experimental study focuses on female mate choice in the sand goby, Pomatoschistus minutus. Females were found to choose males with eggs in their nests. In addition, hatching success increased with clutch size, mainly because males with larger clutches showed less filial cannibalism. Increased egg survival in large clutches may thus be explained by a combination of the dilution effect and higher parental investment. In another experiment, females did not seem to copy the observed mate choice of other females. In conclusion, female preference for males with eggs in their nests is adaptive, and can be explained by direct benefits, as more surviving offspring are produced. Received: 23 December 1995/Accepted after revision: 11 May 1996     

Repeatable female preferences, mating order and mating success in the poeciliid fish, Heterandria formosa

Sexual selection via female choice can afford preferred males comparably higher mating success than those males that lack preferred traits. In addition, many models of sexual selection assume that both male traits and female preferences are heritable. In this study we test whether females of the poeciliid fish, Heterandria formosa, have repeatable pre-copulatory preferences for larger males. We also test whether female pre-copulatory preferences are always reliable indicators of male mating success. When given a choice between a large and a small male, females prefer larger males, and the repeatability of this preference is high. Although there are no overall differences in male mating success between large and small males, large males have a higher mating success when they are the first to mate than when they are the second to mate. Likewise, preferred males also have higher mating success when they are the first to mate than when they mate second. Therefore, the repeatable female preferences observed in this study only predict male mating success when the preferred male mates first. These results illustrate that even significantly repeatable female preferences do not translate into male mating success, which is an assumption of many examinations of the importance of female choice in sexual selection.     

Costs of courtship and mating in a sexually cannibalistic orb-web spider: female mating strategies and their consequences for males

The costs of courtship and mating may include increased risks of predation, the transmission of pathogens, and a loss of foraging opportunities. Thus, a female's decision to tolerate a courting male will depend upon how these costs offset the benefits of mating, which will depend on her reproductive and nutritional status. While these costs may be similar for mated and unmated females, the benefits of mating will be less for mated than virgin females. However, the cost of lost foraging opportunities may be higher for females with fewer nutritional reserves necessary for forming eggs. We examined how these costs and benefits influence the courtship and mating behaviour of male and female orb-web spiders, Argiope keyserlingi. In the field, females on webs that also contained a courting male intercepted fewer prey items per hour than females on webs without a male. In the laboratory, the presence of a courting male at the hub also attracted mantid predators to the web, increasing the risk of predation for both male and female. Staged mating experiments in the laboratory revealed that the frequency of female attacks and pre-copulatory cannibalism was greater among mated than virgin females. Feeding history did not affect aggression in virgin females but, among mated females, food-deprived spiders attacked and cannibalized males more frequently than sated females and only the latter ever remated. These differences in female behaviour influenced male mating strategies. Choice experiments demonstrated that males preferred to venture onto the silk threads of virgin rather than those of mated females. Similar patterns of mate selectivity were observed in the field; females with narrow abdomens attracted more males to the webs than females with broad abdomens, and copulations were observed more frequently among females with narrow abdomens. These smaller females are likely to be virgins that have recently molted. Males that preferentially mate with virgin females will not only avoid potentially fatal attacks but also obtain, on average, a higher fertilization success.     

Mate with the young, kill the old: reversed sexual cannibalism and male mate choice in the spider Micaria sociabilis (Araneae: Gnaphosidae)

Female mate choice is regarded as a strong selective force that significantly affects male mating success. In extreme cases, mate rejection can result in sexual cannibalism. However, males may choose between their partners as well. The killing of potential female mates, i.e. reversed form of sexual cannibalism, may be related to male mate choice. We examined male mate choice in the spider Micaria sociabilis, focusing on the roles of female mating status (virgin/mated), size and age. Reversed cannibalism reached its highest frequency in the period of generation overlap, i.e. when young males from the summer generation met old(er) females from the spring generation. These results suggest discrimination against old(er) females. The frequency of cannibalism was not affected by female mating status or female size. However, larger males from the summer generation were more cannibalistic than smaller males from the spring generation. We conclude that reversed sexual cannibalism might be an adaptive mate choice mechanism and can be explained in the context of the aggressive spillover hypothesis.     

The efficacy of female choice in chimpanzees of the Taï Forest, Côte d’Ivoire

Male–male competition has historically been considered the major force driving sexual selection. However, female choice and inter-sexual conflict are increasingly recognized as important influences affecting differential mating and reproductive success. Many females exhibit preferences for particular males; however, male strategies may conflict with females’ ability to obtain their mate preferences. To influence paternity, females must affect both (1) whether or not sexual interactions occur, particularly during the periovulatory period (POP) and (2) the outcome of sexual interactions. This study focuses on the effectiveness of female choice in wild chimpanzees (Pan troglodytes verus). Over 2,600 h of data were collected on two habituated chimpanzee communities in the Taï National Park, Côte d’Ivoire. Female mate preferences were measured by quantifying proceptive and resistance behavior toward males in both the periovulatory period and non-POP phases of estrus. The efficacy of female preference was measured both (1) by measuring success rates of female proceptivity and resistance behaviors and (2) by determining how well measures of female mate preference (proceptivity and resistance rates) predict male mating success. Though male chimpanzees are clearly dominant to females, the results indicate that females could effectively resist male solicitations and, in most cases, unwanted copulations were averted. Both female proceptivity and resistance rates correlate (positively and inversely, respectively) with male mating success in POP. Outside POP, female proceptivity rates corresponded with male mating success, but resistance rates did not. Males (irrespective of rank) that were preferred by females obtained higher mating success compared to other males during the POP, suggesting that females were effective in their mate choice and that, despite clear male dominance, female choice influences paternity in wild chimpanzees.     

Mate preferences in <Emphasis Type="Italic">Drosophila</Emphasis> infected with <Emphasis Type="Italic">Wolbachia</Emphasis>?

The maternally inherited bacterium Wolbachia pipientis generates strong reproductive incompatibilities between uninfected females and infected males (cytoplasmic incompatibility), significantly reducing both female and male reproductive success. Such fitness costs are thought to place selective pressure on hosts to evolve pre-copulatory preferences for mating with compatible mates, thereby enabling them to avoid the reproductive incompatibilities associated with Wolbachia. Therefore, uninfected females are predicted to prefer mating with uninfected males, whereas infected males are predicted to prefer mating with infected females. Despite these predictions, previous investigations of pre-copulatory mate preferences in Wolbachia-manipulated Drosophila have not found evidence of female preference for uninfected or compatible males. However, none of these studies utilised a design where focal individuals are provided with a simple choice in a relatively non-competitive situation. We examined both female and male pre-copulatory mate preference based on mate infection status in Drosophila simulans and D. melanogaster using simple choice assays involving between 30–50 replicates per treatment. Although we found no evidence of female pre-copulatory mate preferences in either species, male D. simulans exhibited some preference for mating with females of the same infection status. However, this preference was not evident when we repeated the experiment to confirm this finding. Consequently, we conclude that neither male nor female D. melanogaster and D. simulans exhibit significant Wolbachia-associated pre-copulatory mate preferences.     

Age-related female mating decisions are condition dependent in wolf spiders

Female mating behaviors are known to be sensitive to a variety of individual factors both external and internal to a female; however, mating decisions are likely due to a suite of interacting factors. By independently manipulating female and male diet in the wolf spider Rabidosa rabida and testing females across age groups, we demonstrate that, in addition to its independent effect, female nutritional condition interacts with female age to influence female mating behavior. Overall, high-quantity diet (HD) females were more likely to mate than low-quantity diet (LD) females. Within the LD females, older individuals were more likely to mate than younger individuals, while within HD females, mating probabilities were equal across females of different age classes. With respect to mate choice, only female age influenced the likelihood of mating based on male diet. Young females were choosier as they were more likely to mate with HD males than LD males; in contrast, older females were equally likely to copulate with males of each diet treatment. In addition, the likelihood of pre-sexual cannibalism was dependent on both female and male diet. High-quantity diet females were more likely to cannibalize than LD females, and attacks were directed towards LD males most often. We discuss our results in terms of costs versus benefits of female mate choice.     

Sex-specific conditional mating preferences in a cichlid fish: implications for sexual conflict

Conditional mating strategies enable individuals to modulate their mating behaviour depending on ‘individual status’ to maximise fitness. Theory predicts that variation in individual quality can lead to differences in mating preferences. However, empirical evidence is scarce particular in terms of variation in male and female strategies. Here, we experimentally investigated quality-dependent variation in mating preferences concerning reliable quality indicators in Pelvicachromis taeniatus, a colourful cichlid fish with mutual mate choice and ornamentation. Males as well as females were artificially manipulated in phenotypic quality by different feeding regimes. Ornamentation was connected to individual quality in both sexes. Males and females showed conditional mating strategies in different directions. Males showed prudent choice by preferring females of similar quality. In contrast to males, low-quality females preferred highly ornamented males, whereas high-quality females showed neither preferences for high- nor for low-quality males. The results suggest that individuals aim for specific benefits depending on individual quality. Furthermore, the conflicting conditional mating preferences of males and females might lead to sexual conflict, implicating a highly dynamical mating system that evolves even in absence of environmental changes.     

Indirect fitness benefits are not related to male dominance in a killifish

Recent theoretical and empirical studies have shown that male dominance is often at odds with female mate preference and that indirect (genetic) benefits of mate choice may not be related to male dominance. We tested whether female preference corresponded to male dominance and whether mating with dominant males conveyed benefits to offspring fitness in a small freshwater fish, the African annual killifish Nothobranchius korthausae (Cyprinodontiformes), a species without parental care. The experimental design used controlled for the effect of male age, possibility of sperm and egg depletion, and accounted for a potential that females express their preference through maternal effects by manipulation of egg mass during ovulation. By sequentially mating females with males of known dominance, we found that female N. korthausae showed no mate preference in terms of egg numbers deposited with respect to male dominance or body size and no congruent mate preference to specific males was detected. However, males sired offspring with consistently higher hatching success and the effect was repeatable across individual females. Thus, some males provided females with indirect benefits related to additive genetic quality (“good genes”) and expressed via increased hatching rate, but this benefit was not related to male dominance status or body size.     

Responses of female lizards,<Emphasis Type="Italic"> Lacerta monticola</Emphasis>, to males' chemical cues reflect their mating preference for older males

Female mate choice based on visual traits appears to be rare in lizards. Field observations suggest that females of the lizard Lacerta monticola preferred to mate with larger/older males. Although older males are usually green and larger, and younger males brown and smaller, there is some overlap in size and coloration between age classes. Thus, visual cues may not always be reliable indicators of a male's age. We hypothesized that female mate-choice preferences may be based on males' pheromones, which might transmit information about characteristics such as age. In a laboratory experiment, we analyzed the effect of age of males on attractiveness of their scents to females. When we offered scents of two males of different age, females associated preferentially with scents of older males. This suggested that females were able to assess the age of males by chemical signals alone, and that females preferred to be in areas scent-marked by older males. Thus, females may increase their opportunities to mate with males of high quality, or may avoid harassment by sneaking young males. This result agreed with field observations on females mating with old males, and rejection of advances by young males. Our results also suggested that female preference for older males may depend on their own body size. Large females showed a strong preference for older males, whereas smaller females were not so selective. This, together with males' preference for large females, might lead to size-assortative matings. We suggest that the quality and/or quantity of male pheromones could communicate to the female heritable male genetic quality (i.e. age) and thereby serve as the basis of adaptive female choice in lizards.Communicated by W.E. Cooper     

Polyandry, multiple mating, and female fitness in a water strider Aquarius paludum

Contrary to Bateman’s principle, polyandry appears to be a common female mating strategy. Several hypotheses have been proposed to explain the evolution of polyandry. It is assumed that females gain either material or genetic benefits from multiple matings, or that they are coerced into mating by males. In water striders, mating is generally assumed to be costly to females, and they are thought to mate for reasons of convenience, adjusting their resistance to mating according to male harassment. Here, we tested the effect of number of matings (with the same male) and number of partners on female fitness in a water strider Aquarius paludum. In the first experiment, we regulated the time females spent with a male and found that females’ egg production increased with multiple matings up to a point. The result supports the existence of an optimal female mating frequency. In the second experiment, we tested how polyandry affects the number of eggs laid and egg hatching success. We conducted three different trials: females mated four times with either a single male, two different males, or with four different males. Females that mated with four different males laid the lowest number of eggs and had the lowest egg hatching success, suggesting that polyandry reduces females’ egg production and egg hatching success in A. paludum. We conclude that A. paludum females probably gain material benefits from mating but no genetic benefits were found in this study.     

Selection for male choice based primarily on mate compatibility in the oldfield mouse, Peromyscus polionotus rhoadsi

Despite the consensus that mate choice acts as a mechanism for selection of secondary sexual traits, the evolutionary forces affecting mate preferences themselves remain controversial. In this study, we first demonstrated selection acting directly on the mate preferences of monogamous male oldfield mice, Peromyscus polionotus rhoadsi. One group of male oldfield mice were allowed to express a social preference between two potential mates, and were subsequently paired with either their preferred or rejected female. Among these pairs, those containing preferred females produced more offspring than did those containing rejected females. We next demonstrated that this fitness advantage depended primarily on compatibility between the members of a mated pair. A second group of male oldfield mice were not allowed the opportunity to express a social preference between potential mates. Rather, these males were paired with females that had been either preferred or rejected by males in the first group. Among these pairs, those containing preferred females did not produce more offspring than those containing rejected females. In other words, individual mate preferences had fitness consequences only for those males that expressed them, demonstrating that these preferences were based primarily on compatibility between mates.     

The cost of parental care and egg cannibalism in the river bullhead,Cottus gobio L. (Pisces,Cottidae)

Summary Male river bullheads guard and care for egg masses during a single brood cycle every breeding season. A study of two bullhead populations demonstrated that nesting males show a strong reduction in food intake rate and that their physical condition deteriorates during parental care. The estimated weight loss for the average guarding male was 18.8% in one population and 13.5% in the other. This could in part be responsible for the peak of male mortality observed during the second part of the breeding season. A high incidence of egg cannibalism was observed in males guarding eggs. Analysis of the developmental stage of individual egg masses demonstrated that heterocannibalism is very rare in this species and that the observed rate of egg cannibalism is mainly due to guarding males preying upon their own eggs (filial cannibalism). In both populations the frequency of filial cannibalism was negatively correlated with the male's chance of getting other food items. The probability of a male cannibalizing its own eggs was also significantly influenced by the time elapsed since the beginning of parental care. The observed limited cannibalism of progeny in the river bullhead cannot be explained as a male's strategy for obtaining energy to be used in subsequent brood cycles, as suggested for other fishes which show filial cannibalism. Rather, it can be interpreted as a behaviour aimed at avoiding the risk of dying of starvation before the eggs hatch. The observed criteria of female mate choice, i.e. a preference for males in good physical condition and for males that already have eggs in their nests, are consistent with the prediction of Rohwer's filial cannibalism theory, although other hypotheses cannot be excluded.     

Mate availability accelerates male filial cannibalism in a nest brooding fish: effects of number and fecundity of females

Theoretical models predict that increased mate availability accelerates filial cannibalism by the parental male, but we do not yet fully understand how the various aspects of mate availability contribute to this effect. We examined the effects of two elements of mate availability—female fecundity and sex ratio—on filial cannibalism by the lizard goby, Rhinogobius flumineus, which is a paternal nest brooding fish. We used three types of females (stimulus-females): a single female with slim belly (not ready to spawn), a single gravid female (ready to spawn), and two gravid females. Stimulus-females were housed in a transparent cage and shown to subject males just before and after spawning with a separate female, after which males cared for the brood. A single gravid stimulus-female accelerated filial cannibalism, compared with a control-stimulus consisting of an empty cage, but only during the early care period. In contrast, a single slim-bellied stimulus-female did not accelerate cannibalism. A stimulus of two gravid females accelerated cannibalism to the same degree as a single gravid female stimulus. Our results suggest that in lizard gobies, filial cannibalism by parental males is accelerated by female quality (fecundity) in the early care period, but not by a higher number of available females (sex ratio).     

Factors influencing sexual cannibalism and its benefit to fecundity and offspring survival in the wolf spider Pardosa pseudoannulata (Araneae: Lycosidae)

Sexual cannibalism is hypothesized to have evolved as a way to obtain a high-quality meal, as an extreme mate choice or as a consequence of female aggressive spillover. Here, we examined underlying factors likely to influence sexual cannibalism in the wolf spider Pardosa pseudoannulata (Bösenberg & Strand, 1906) from China, including mating status, female egg-laid status, female hunger level, female adult age and mate size dimorphism. The results showed that about 10 % of P. pseudoannulata virgin females cannibalized the approaching males before mating and that 28 % of P. pseudoannulata virgin females immediately cannibalized the males after mating. No incidents of sexual cannibalism during copulation were observed. Before mating, previously mated females and starved females tended to engage in significantly higher rates of attacks compared to virgin and well-fed females. Females that had laid egg sacs tended to engage in a significantly higher rate of attacks and sexual cannibalism than virgin females before mating. Regardless of pre- or post-mating, there was a strong positive relationship between mate size dimorphism and the occurrence of sexual cannibalism. We also tested the effects of sexual cannibalism on the fecundity of cannibalistic females and the survival of their offspring. Our results indicated that sexual cannibalism affected positively the offspring survival of cannibalistic females, but not fecundity. Our findings support the hypothesis that sexual cannibalism has evolved as an adaptive component of female foraging strategy and that it benefits offspring survival as a result of paternal investment.     

The effects of mating system on male mate choice in a coral reef fish

Summary We show how mate limitation appears to be critical in determining whether or not males exercise mate choice among available females. Thalassoma bifasciatum is a Caribbean reef fish with two distinct mating patterns: group-spawning and pair-spawning. In both mating systems, female fecundity is variable and size dependent, and female availability is high. However, sperm competition among group-spawning males apparently limits the number of effective matings in which a male may engage, whereas territorial pair-spawning males have little or no such limitation. Group-spawning males should be discriminating in their choice of mates and our data confirm this: there is strong evidence for assortative mating in group-spawns, with more large males joining in mating groups around large females. In contrast, pair-spawning males show no indication of mate preferences, and spawn with all females who arrive at their territories.     

Do female association preferences predict the likelihood of reproduction?

Sexual selection acting on male traits through female mate choice is commonly inferred from female association preferences in dichotomous mate choice experiments. However, there are surprisingly few empirical demonstrations that such association preferences predict the likelihood of females reproducing with a particular male. This information is essential to confirm association preferences as good predictors of mate choice. We used green swordtails (Xiphophorus helleri) to test whether association preferences predict the likelihood of a female reproducing with a male. Females were tested for a preference for long- or short-sworded males in a standard dichotomous choice experiment and then allowed free access to either their preferred or non-preferred male. If females subsequently failed to produce fry, they were provided a second unfamiliar male with similar sword length to the first male. Females were more likely to reproduce with preferred than non-preferred males, but for those that reproduced, neither the status (preferred/non-preferred) nor the sword length (long/short) of the male had an effect on brood size or relative investment in growth by the female. There was no overall preference based on sword length in this study, but male sword length did affect likelihood of reproduction, with females more likely to reproduce with long- than short-sworded males (independent of preference for such males in earlier choice tests). These results suggest that female association preferences are good indicators of female mate choice but that ornament characteristics of the male are also important.     

Prior encounters with the opposite sex affect male and female mating behavior in a wolf spider (Araneae,Lycosidae)

Mate availability can vary widely in nature depending upon population density and sex ratio and can affect the ability of individuals to be selective in mate choice. We tested the effects of prior encounters with the opposite sex (i.e., exposure to the opposite sex either with or without mating) on subsequent mating behavior in two experiments that manipulated mate availability for both males and females in the wolf spider, Hogna helluo. The probability of mating in the experimental trial depended upon whether the prior encounter involved mating or not, and males and females responded in opposite directions. Exposure without mating resulted in a higher subsequent frequency of mating for females and a lower subsequent frequency of mating for males, while prior mating experience resulted in a lower frequency of female remating and a higher frequency of male remating. Prior exposure without mating did not affect female aggression. However, mated females engaged in precopulatory cannibalism more frequently than virgins. Mated males escaped postcopulatory cannibalism more frequently than virgins. Our results show that males respond to exposure without mating in the expected manner. However, prior mating (1 week earlier) had unexpected effects on males, which may be due to mated males being of higher quality. There were little or no effects of the size of the prior exposure individual or mate on subsequent mating behaviors. Further research is needed to determine why different species use different degrees of prior information in mate choice.     

Audience effect alters male but not female mating preferences

Males often face strong mating competition by neighboring males in their social environment. A recent study by Plath et al. (Anim Behav 75:21–29, 2008a) has demonstrated that the visual presence of a male competitor (i.e., an audience male) affects the expression of male mating preferences in a poeciliid fish (Poecilia mexicana) with a weaker expression of mating preferences when an audience male observed the focal male. This may be a tactic to reduce sperm competition, since surrounding males likely share intrinsic preferences for female traits or copy mate choice decisions. Here, we examined the hypothesis that a same-sex audience would affect female mate preferences less than male mating preferences. Our hypothesis was based on the assumptions that (1) competition for mates in a fashion that would be comparable in strength to sperm competition or overt male–male aggression is absent among Poecilia females, and (2) P. mexicana females typically form female-biased shoals, such that almost any female mate choice in nature occurs in front of a female audience. Poecilia females (P. mexicana, surface and cave form, and the closely related gynogenetic Poecilia formosa) were given a choice between a large and a small male, and the tests were repeated while a conspecific, a heterospecific, or no audience female (control) was presented. Females spent more time in the neutral zone and, thus, less time near the males during the second part of a trial when an audience was presented, but—consistent with predictions—females showed only slightly weaker expression of mate preferences during the second part of the tests. This decline was not specific to the treatment involving an audience and was significantly weaker than the effect seen in the male sex.     

Sexual dimorphism and male mating success in the tentacled blenny, <Emphasis Type="Italic">Parablennius tentacularis</Emphasis> (Teleostei: Blenniidae)

Although external sexually dimorphic traits are commonly found in males of combtooth blenny species, little is known about the benefit they can convey to male mating success. Indeed, while female preferences for large males have been demonstrated in some species, the possible role played by dimorphic ornaments has been neglected. We now report on the tentacled blenny, Parablennius tentacularis, a species where males are characterized by bulb glands on the anal fin and both sexes exhibit a dark spot on the dorsal fin and orbital tentacles. Males are territorial, make nests in empty bivalve shells, and provide solitary parental care for the eggs. Using morphometric analysis and field collected data on male and female external features, nest characteristics and number of eggs in the nests, we have assessed the development of dimorphic traits in both sexes and male mating success. The results reveal that orbital tentacles of males are more developed and more variable in size than those of females. Larger males exhibit longer orbital tentacles and larger anal glands but do not necessarily occupy larger nests. Male mating success is significantly correlated with the inner nest surface area and with orbital tentacle size but not with body size. These results provide support for a primary role of male ornaments in enhancing blenny male mating success and are discussed in the context of mate choice for direct and indirect benefits.