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.     

Male preference for colourful females affected by male size in a marine fish

It is becoming increasingly clear that mate preferences are not static, but can vary as a function of ecological conditions and the state of the choosing individual. This applies not only to females, the sex that has usually been the subject in research on mate preferences, but also to males. Under certain conditions, males should be selective in their choice of breeding partner. In the two-spotted goby, Gobiusculus flavescens, a small marine fish, breeding females develop conspicuous yellow-orange bellies, which they actively display to males during courtship. We have recently shown that males prefer more colourful females as mates. In this study, we test if the size of a male affects his preference for colourful females. Using three-compartment mate-choice aquaria, we recorded the interest shown by a male in two females differing in coloration but similar in size. Large and small males were equally eager to court females, but only large males showed a greater interest in the more colourful females. We suggest that small males are unselective because they usually obtain few mating opportunities, as a result of being unsuccessful in mate attraction or male contest competition. This study provides the first demonstration that the size of a male affects his preference for female colour.     

Sexual selection in darkness? Female mating preferences in surface- and cave-dwelling Atlantic mollies,<Emphasis Type="Italic"> Poecilia mexicana</Emphasis> (Poeciliidae,Teleostei)

In many species, females prefer large males as mating partners. Male size can easily be determined visually. We examined how such mate choice evolves when individuals are deprived of sensory information previously used to determine male quality. Using a cave-dwelling population of Atlantic mollies, Poecilia mexicana, as a model, we asked whether the female mating preference for large male body size still occurs in this cave fish, or whether it is lacking due to the absence of visual communication in the cave environment. In simultaneous choice tests we compared the time females spent with a large or a small male. In the river-dwelling and cave-dwelling fish, as well as the population originating from the cave entrance, we found a significant preference for large males in light. Hence, the ancestral mating preference of surface-dwelling mollies has been maintained during the evolution of the cave form. However, only the cave population exhibited a mating preference in darkness. Determination of male body size appears to have been taken over by a non-visual sensory system, probably the lateral line.Communicated by K. Lindström     

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.     

Why do female pied flycatchers mate with already mated males: deception or restricted mate sampling?

The polygyny threshold model suggests that females make an optimal choice between mated and unmated males. However; in birds in which males provide parental care, the fitness of secondary females is often lower than expected from this model. This has been explained by the deception hypothesis, which states that males hide their mating status and deceive females into polygyny. Yet there is no direct evidence that secondary females are unaware of male mating status when they settle. Alternatively, females settle with mated males as a result of mate competition and costs of searching. We used videofilming at nestboxes defended by males to study mate sampling of female pied flycatchers Ficedula hypoleuca. The females visited on average only 2.74 males (range 1–8, n = 43). Most (16 of 19) of the polygynous matings occurred because females had only visited mated males, or the unmated males visited became occupied by competitors during the sampling period. Among females that could choose between both mated and unmated males, the majority (13 of 16) settled with unmated males. These results lend little support to the deception hypothesis but are consistent with the view that females are able to detect male mating status but sometimes settle with mated males because of cost of searching. Prospecting females seemed willing and able to suffer the cost of fighting with aggressive primary females in the males' secondary territory if no alternative mating options were available. In addition to male mating status, females took male quality (plumage colour, age) into account in mate choice but the former appeared to be the more important. Correspondence to: T. Slagsvold     

Female mate choice in the non-territorial lizard Ameiva plei (Teiidae)

Mate choice by females has been documented in a variety of taxa. Female mate choice in species lacking male resource control or paternal care might occur if preferred males provide protection from harassment. Female mate choice was investigated in a natural population of the non-territorial lizard Ameiva plei (Teiidae). Consort pairs were allowed to form naturally. Consort males were significantly larger than non-consort males. After removal of consort males, the “abandoned” female's reaction to the first male who approached her was recorded. Females rejected all small males. Female preference for large males was significantly higher than preference for small males. Large males may be better equipped to guard the females from harassment and behavior of large males is less harassing than behavior of small males, thereby affording the female increased foraging time. Received: 21 June 1996 / Accepted after revision: 28 December 1996     

No relationship between long-distance acoustic mate attraction signals and male fertility or female preference in spring field crickets

To father offspring, a male must succeed at two processes of sexual selection: (1) mate with a female and (2) fertilize her eggs. We investigated the relationships between pre- and post-copulatory male traits and female mating responses in wild-captured and laboratory-reared spring field crickets, Gryllus veletis. The phenotype-linked fertility hypothesis suggests that females may receive a direct benefit, enhanced fertilization efficiency, by mating with males that signal attractively. We measured fine-scale components of male acoustic mate attraction signals as well as how much time males spent signalling, measured female preference for males in mating trials and then quantified sperm number and viability. We found no relationship between male signalling traits and male fertility or female preference, providing no evidence for the phenotype-linked fertility hypothesis. We also found no difference in sperm metrics between wild-captured and laboratory-reared males. While female crickets may receive benefits by choosing males based on acoustic signal characteristics, whether the benefits are a result of genetic quality, seminal fluid contents or some other male trait remains unknown.     

Asexuals looking for sex: conflict between species and mate-quality recognition in sailfin mollies (Poecilia latipinna)

When two closely related species are sympatric the process of species recognition (identifying conspecifics) and mate-quality recognition (increased fitness benefits) can yield a conflict when heterospecifics resemble high-quality conspecifics. Conflict in species versus mate-quality recognition may serve as a possible mechanism for the persistence of unisexual, gynogenetic Amazon mollies (Poecilia formosa). Amazon mollies require sperm from closely related species (e.g., sailfin mollies, P. latipinna) to start embryogenesis but inheritance is strictly maternal. When choosing mates, male sailfin mollies from populations sympatric with Amazon mollies may rely on traits indicating species identity rather than those indicating mate quality. Conversely, males from allopatric populations may rely more on traits indicating mate quality. Previous work has found that male sailfin mollies in sympatry exhibit a significantly greater mating preference for female sailfin mollies over Amazon mollies compared to males in allopatry. In addition, male sailfin mollies prefer to associate with and produce more sperm in the presence of larger conspecific females, which are more fecund. We hypothesized that male sailfin mollies experience a conflict in species recognition and mate-quality recognition in the presence of Amazon mollies that are relatively larger than female sailfin mollies. To test this hypothesis, we paired males from sympatric and allopatric populations with a larger Amazon molly and a smaller female sailfin molly. We scored the number of mating attempts that males directed to conspecific and heterospecific females. Males in most sympatric and allopatric populations demonstrate no clear preference for conspecifics. In addition, we found some evidence for a difference in mating preference between allopatric and sympatric populations with males from allopatry showing a greater heterospecific mate preference. These results indicate a conflict between species and mate-quality recognition. In sympatry this conflict may contribute to the persistence of gynogenetic Amazon mollies.     

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.     

The lexicon of love: what cues cause size-assortative courtship by male garter snakes?

Cues that females use to select potential mates have attracted substantial research effort, but the criteria for male mate choice remain very poorly known. Red-sided garter snakes ( Thamnophis sirtalis parietalis) court and mate in large aggregations around overwintering dens in southern Manitoba, Canada. Both courtship and mating are size-assortative: small male snakes court small as well as large females, whereas larger males court only large females. This system provides a unique opportunity to assess the cues that males use in selecting mates, and in particular the mechanisms that generate a size-related shift in mate preference. Experiments in which we manipulated body sizes and scents showed that both vision and scent (sex pheromones) were important. Large males directed intense courtship only when the stimulus provided both visual and chemical (skin lipid) evidence of large body size. Small males were much less discriminating in both respects. Thus, size-assortative mating in this system is generated not by larger males excluding their smaller rivals from the largest females (as has been reported in other reptile species), but by a size-related shift in the visual and pheromonal cues that elicit courtship. Males of some species may thus show complex patterns of mate choice, with the cues that stimulate courtship differing even among males within a single population based on traits such as age or body size.     

Direct male-male competition can facilitate invasion of new colour types in Lake Victoria cichlids

The possibility that disruptive sexual selection alone can cause sympatric speciation is currently a subject of much debate. The initial difficulty for new and rare ornament phenotypes to invade a population, and the stabilisation of the resulting polymorphism in trait and preference make this hypothesis problematic. Recent theoretical work indicates that the invasion is facilitated if males with the new phenotype have an initial advantage in male-male competition. We studied a pair of sympatric incipient species of cichlids from Lake Victoria, in which the red (Pundamilia nyererei) and blue males (P. pundamilia) vigorously defend territories. Other studies suggested that red phenotypes may have repeatedly invaded blue populations in independent episodes of speciation. We hypothesised that red coloration confers an advantage in male-male competition, assisting red phenotypes to invade. To test this hypothesis, we staged contests between red and blue males from a population where the phenotypes are interbreeding morphs or incipient species. We staged contests under both white and green light condition. Green light effectively masks the difference between red and blue coloration. Red males dominated blue males under white light, but their competitive advantage was significantly diminished under green light. Contests were shorter when colour differences were visible. Experience of blue males with red males did not affect the outcome of a contest. The advantage of red over blue in combats may assist the red phenotype to invade blue populations. The apparently stable co-existence of red and blue incipient species in many populations of Lake Victoria cichlids is discussed.Communicated by C. St. Mary     

Male choice

Summary Male preference for large females as mates was demonstrated in the wood-boring weevil, Brentus anchorago (Coleoptera: Brentidae) by observation and by mate choice experiments in which the complicating factor of male rivalry was eliminated. Adult weight varied at least 23-fold in a large breeding aggregation in Panama. Drilling females guarded by males were larger than unguarded drilling females, and the number of males attending a drilling female increased with length of the female. Thus despite a sex ratio of about 1:1, males were unevenly distributed among the females. A male attending a female had on average about 1 rival male in his vicinity (Lloyd's Index of Mean Crowding). Male preference for large females in the absence of rival males was directly tested in choice arenas on the surface of the host tree. When a large and a small female were simultaneously presented, large and small males alike mated first with the large female. Male choice of large females is probably adaptive in Brentus anchorago because larger females lay larger eggs, which produce larger offspring in a competitive larval environment. Male choice in this species is associated with high male mating investment and time commitment per female, and not with high male parental investment.     

The effects of male–male contests and female eavesdropping on female mate choice and male mating success in the jumping spider, <Emphasis Type="Italic">Thiania bhamoensis</Emphasis> (Araneae: Salticidae)

In experiments that comprised of three phases (fight, choice, and mating) under “seen” and “unseen” conditions, we examined the effects of the outcomes of male–male contests and female eavesdropping on female mate choice and male mating success in the fighting spider, Thiania bhamoensis (Salticidae). The results revealed female eavesdropping on agonistic interactions. Females that had watched an aggressive interaction showed no distinctive preference for the winner over the loser, but they preferred the loser when they had not observed a fight. Winners, however, achieved a greater mating success than did losers during the mating phase. Gaining access to females was based on the insistence of the winners in courtship in terms of the number of quivers, rather than on the fighting behavior of the males. Hence, the outcome of male–male contests may not be an important determinant of a male’s mating success in T. bhamoensis. Instead, courtship display plays an important role in determining the success of male mating in this species. This study also suggests that female mate preference may not be a good indicator of eventual female mate choice and male mating success. Thus, a causal relationship between female mate preference and male mating success cannot be inferred. Joanna P. Y. Chan, Pei Rong Lau, and Ai Jie Tham contributed equally.     

Female reactions to male absence after pairing in the pied flycatcher

Mating with an already mated pied flycatcher (Ficedula hypoleuca) male is costly for a female. Two hypotheses explain why some females still mate with already mated males. The deception hypothesis suggests that some females mate with already mated males since it is difficult to assess perfectly the mating status of a male with separate territories (polyterritoriality). The search cost hypothesis states that females are aware of male mating status but the costs of searching for an unmated male exceed costs associated with the status of secondary female. One potential cue that could disclose a male's mating status is the existence of brief visits to the primary territory by polyterritorial males. To mimic such visits I removed the male from the territory for 60 min soon after female settlement. Only few females abandoned their mates as a consequence of male removal even though they had available unmated males close by. This result is most consistent with the deception hypothesis. Females did not use occasional male absence as a cue to avoid presumably polyterritorial males and in this respect they were not perfect in assessing males.     

Temporal constraints and female preference for burrow width in the fiddler crab, <Emphasis Type="Italic">Uca mjoebergi</Emphasis>

We studied sampling behaviour and mate choice in the fiddler crab Uca mjoebergi. Once a female selects a mate, she copulates in his burrow and remains there until releasing her aquatic larvae. U. mjoebergi occurs in habitats that are inundated only by the highest amplitude spring tides. Females can only release their larvae during these tides, and release before or after will result in complete failure of reproductive effort. Matings occur over a 5-day period near the end of neap tides. Our results suggest that within the mating period, females adjust their larval developmental rates by selecting specific burrows in which to incubate their clutches. We found that at the start of the mating period, females chose larger males as mates. Since male size was positively correlated to burrow width, females were selecting wide burrows and effectively incubating at lower temperatures. This would slow down the developmental rates of larvae. In contrast, females that mated late in the mating period selectively chose small males. By incubating in narrower, warmer burrows, these females may increase the developmental rates of larvae. We propose that females are selecting burrows to influence incubation rate and ensure timely release of their larvae. Female U. mjoebergi appear to adjust their preference for the direct benefits of mate choice to increase their reproductive success.     

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.     

Bushcricket song as a clue for spermatophore size?

Bushcricket males of Poecilimon zimmeri transfer large and protein-rich spermatophores during mating, which females directly ingest. There is correlational evidence that heavier males transfer larger nuptial gifts. In no-choice mating trials, females mated randomly with respect to male’s body weight. In contrast, in two-choice mating trials, female bushcrickets exhibit clear choice for the heavier male. This heavier male advantage was also found in pre-mating choice during phonotaxis. With manipulated mute males, females mated at random with regard to body weight of the competitors. The number of physical encounters between a female and males was low in all tests with a single male (no choice) and greater in choice-tests with two competing males. The latencies to mate also differed significantly between treatments. The time mating pairs spent in precopula was short in experiments where the males could hear rivals and significantly longer in all other tests using either a single male or mute males. Thus, acoustic signalling in male bushcrickets seems to signal male body weight. A preference for heavier males may reflect a female’s preference for a larger spermatophore and therefore a greater direct benefit.     

Female mate choice in the zebra finch — the effect of male beak colour and male song

Studies of female mate preference in zebra finches (Taenopygia guttata) have shown that male beak colour and song rate are important. However, the two characters are correlated. Here the effect of beak colour and song rate on female choice are examined independently. In mate choice tests involving two males, beak colour was manipulated artificially using nail varnish. The results showed that females showed a significant preference for males with a high song rate, but not with a red beak. Females did not prefer males with a red beak if song rate was low and females preferred males with orange beaks who expressed a high song rate. Female preference for males with red beaks was not found when beak and song characters were no longer correlated.     

Body size preferences in the pot-bellied seahorse <Emphasis Type="Italic">Hippocampus abdominalis:</Emphasis> choosy males and indiscriminate females

Male seahorses (genus Hippocampus) provide all post-fertilization parental care, yet despite high levels of paternal investment, these species have long been thought to have conventional sex roles, with female mate choice and male–male competition. Recent studies of the pot-bellied seahorse (Hippocampus abdominalis) have shown that sex-role reversal occurs in high-density female-biased populations, indicating that male mating preferences may lead to sexual selection on females in this species. Egg size, egg number, and offspring size all correlate positively with female body size in Hippocampus, and by choosing large mating partners, male seahorses may increase their reproductive success. While male brood size is also positively correlated with body size, small H. abdominalis males can carry exceptionally large broods, suggesting that the fecundity benefits of female preference for large partners may be limited. We investigated the importance of body size in reproductive decisions of H. abdominalis, presenting focal individuals of both sexes with potential mating partners of different sizes. Mating preferences were quantified in terms of time spent courting each potential partner. Male seahorses were highly active throughout the mate-choice trials and showed a clear behavioral preference for large partners, while females showed significantly lower levels of activity and equivocal mating preferences. The strong male preferences for large females demonstrated here suggest that sexual selection may act strongly on female body size in wild populations of H. abdominalis, consistent with predictions on the importance of female body size for reproductive output in this species. An erratum to this article can be found at     

Badge size in the house sparrow Passer domesticus

Summary I studied female mate choice in house sparrows Passer domesticus in relation to the size of the black throat patch of males (badge size), which is a signal of dominance status, and to territory quality. Males with large badges obtained a mate earlier in spring than males with small badges. Males which remained unmated during the entire breeding season had smaller badges than mated males, even when controlling for the effect of other morphological traits and age. Largebadged males had territories with more breeding sites than small-badged males. Territories defended by males with large badges primarily had hole nest sites, which were safe from predators, and nestlings rarely fell from hole nests. Females were implanted with estradiol to induce copulation solicitation displays. Females responded more strongly to a male taxidermic mount and song than to song alone, and they responded more strongly and frequently to male mounts with large badges. Female house sparrows chose mates on the basis of male badges and perhaps on the basis of the quality of the nesting territories offered.