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.     

The role of information in mate-choice copying in female sailfin mollies (Poecilia latipinna)

Female mate choice is a complex process involving both genetic and social factors. Extrinsic cues may play a role in determining how these factors interact. Mate-choice copying is a socially influenced mate-choice strategy in which females observe other females during mate choice and choose the same male as those females. Previous studies have shown that female sailfin mollies (Poecilia latipinna) prefer larger over smaller males, and this preference is assumed to be genetically based. In this study we tested, first, whether sailfin molly females changed their mate preference in favour of smaller males when they could obtain more information by observing two model females sequentially for 5 min each or one model female for 20 min next to the smaller male. Second, we tested if females that had changed their preferences in favour of smaller males maintained this learned preference afterwards. In copying experiments, females changed their preferences in favour of smaller males both when they could observe two model females each for 5 min near by a smaller male and when they could observe one model female for 20 min near the smaller male. In the latter case, females maintained this learned preference for smaller males up to 5 weeks after the copying experiment. This shows that mate-choice copying has a long-lasting effect on mate-choice decisions in sailfin molly females and that mate-choice copying can serve as a mechanism for cultural inheritance of mate preferences in females.     

Sexual conflict,sexual selection and sperm competition in the spawning decisions of bitterling, <Emphasis Type="Italic">Rhodeus</Emphasis><Emphasis Type="Italic">sericeus</Emphasis>

Sexual selection may operate through either direct selection on preference genes or indirect genetic benefits. However, in many species both direct and indirect selection may operate and can influence female mate and oviposition choice. Adaptations by males for sperm competition can also affect female mate and oviposition choice and can lead to sexual conflict. We investigated the role of direct and indirect benefits and male adaptation to sperm competition for female oviposition decisions in the bitterling, Rhodeus sericeus, a freshwater fish that spawns on the gills of living unionid mussels. Field experiments showed that females chose mussels for spawning on the basis of the number of embryos already in mussels and the body size and/or extent of red coloration of the eyes of territorial males. There was also a significant interaction between these direct and indirect benefits of oviposition choice. Territorial male bitterling avoided leading females to mussels into which rivals had already released sperm. Males also increased their rate of sperm release into mussels in response to sperm release by sneaking males. We discuss the possibility that sexual conflict in oviposition choice occurs in this species.     

Sexual selection and species recognition in the pygmy swordtail, Xiphophorus pygmaeus: conflicting preferences

Sexual selection and species recognition play important roles in mate choice; however, sexual selection preferences may overlap with traits found in heterospecifics, producing a conflict between sexual selection and species recognition. We examined female preferences in Xiphophorus pygmaeus for male traits that could provide both types of information to determine how females use multiple cues when preferences for these cues would conflict. We also examined X. pygmaeus behavior in the field to determine if females have the opportunity to choose mates. As no male-male competition was observed in the field, and females occasionally chased males from feeding areas, females apparently have the opportunity to exercise mate choice in their natural habitat. In the laboratory, female X. pygmaeus used body size as a sexual selection cue, preferring large heterospecifics (X. cortezi) to small conspecifics. Females also preferred barless X. cortezi over barred X. cortezi when males were size matched. Because X. pygmaeus males do not have bars, this preference suggests that X. pygmaeus females use vertical bars in species recognition, and that large body size and vertical bars are conflicting cues. However, X. pygmaeus females did not have a preference for males of either species when sexual selection and species recognition cues were presented concurrently. This result was surprising, because preferences for species recognition cues are often assumed to be stronger than sexual selection cues. We suggest that females may be using additional species-specific cues in mate choice to prevent hybridization.     

Mate compatibility,parental allocation and fitness consequences of mate choice in the sand goby <Emphasis Type="Italic">Pomatoschistus minutus</Emphasis>

Recent theory and empirical work suggests that there may be variation among females in mate preferences that is adaptive. One of the possible mechanisms maintaining variability in preferences and preferred traits is that the benefits of mate choice may depend on compatibility with potential mating partners. We examined fitness consequences of mate choice in a species of fish, the sand goby, Pomatoschistus minutus with a special focus on mate compatibility. Females were given the opportunity to establish their mate preferences in a dichotomous mate choice experiment. This information was then applied by mating the focal or control female with either the preferred or the non-preferred male. The parental performance of the males of these four mating combinations was then measured. In a separate experiment, we assessed the female differential allocation by determining the residual gonad weight of spawned females as a measure of the proportion of eggs spawned. We also estimated the amount of filial cannibalism separately for both sexes. Our results show that preferred males provided benefits in the form of an increased number of hatching eggs. This benefit was the same when the male was mated with a focal or a control female. Hence, we found no support for benefits that depend on mate compatibility. Neither did we find support for the hypothesis that females would lay a different number of eggs depending on the male status. The results also indicate that male filial cannibalism has a strong role in determining hatching success in this species.     

The assessment of female reproductive state during courtship and scramble competition in the fiddler crab, Uca paradussumieri

Male fiddler crabs, Uca paradussumieri, mate underground during a 4- to 7-day period each full and new moon. As soon as the tide recedes, males enter the burrows of females that will ovulate the following day ('pre-ovigerous' females). Males copulate with and guard these females until they ovulate. When interrupted by an intruding male, the first male to reach the female is usually able to defend her and successfully mate with her. In fiddler crabs, females mate multiply and there is last male sperm precedence. Before each semi-lunar mating period, male U. paradussumieri were more likely to court females with whom they would later mate than other nearby females with whom they did not mate. This suggests that males collect information on female reproductive state prior to the females becoming ovigerous. In this species, aggression was common between males that courted the same female. When previously courted females were approached by other males, the initial courter attempted to forcefully disrupt the courtship. This behavior may allow males the exclusive use of information on female reproductive condition. It also suggests a type of scramble competition between males over females. Furthermore, it indicates that males are able to locate receptive females prior to their becoming ovigerous. The shorter guarding period observed in this species, as compared with other fiddler crabs, is caused by females rejecting longer guarding periods. Male ability to assess female reproductive status may therefore be advantageous because it increases male mating success within a scramble type of competitive polygyny.     

The energetic cost of protogynous versus protandrous sex change in the bi-directional sex-changing fish Gobiodon histrio

To investigate the relative cost of protogynous versus protandrous sex change we induced sex change in each direction in Gobiodon histrio (Gobiidae) and then compared growth, body condition and biochemical condition between sex-changed and non-sex-changed fish in treatment and control groups. Sex change in each direction was induced by establishing pairs of adult males and pairs of adult females on isolated coral colonies. Heterosexual pairs were used as controls. For both males and females, growth and body condition did not vary between fish that changed sex and those that did not. The relatively low cost of sex change, compared to the likely costs of searching for a mate of the correct sex, appears to explain the evolution of bi-directional sex change in coral-dwelling gobies. Lipid concentrations in the liver of males and females that changed sex were reduced by similar amounts (34% and 41%, respectively) compared to male and female controls that did not change sex. Therefore, changes in biochemical condition were approximately equal for fish that sex change in each direction and cannot explain the unequal frequency of sex change in each direction in natural populations of G. histrio.     

Interspecific attractiveness of structures built by courting male fiddler crabs: experimental evidence of a sensory trap

Male fiddler crabs Uca musica sometimes build sand hoods and male Uca beebei sometimes build mud pillars next to their burrows to which they attract females for mating. Mate-searching females preferentially approach these structures and subsequently mate with structure builders. Here we show that the preference for structures is not species-specific and argue that it may not have evolved for mate choice. When not near burrows, many species of fiddler crabs approach and temporarily hide near objects, suggesting that hoods and pillars may attract females because they elicit this general predator-avoidance behavior. To test this sensory trap hypothesis we individually released female U. musica, U. beebei and Uca stenodactylus, a non-builder, in the center of a circular array of empty burrows to which we added hoods and pillars and then moved a model predator toward the females. All species ran to structures to escape the predator and the two builders preferred hoods. Next, we put hood replicas on male U. beebei burrows and pillar replicas on male U. musica burrows. When courted, females of both species preferentially approached hoods as they did when chased with a predator. However, males of both species with hoods did not have higher mating rates than males with pillars perhaps because hoods block more of a male's visual field so he sees and courts fewer females. Sexual selection may often favor male signals that attract females because they facilitate general orientation or navigation mechanisms that reduce predation risk in many contexts, including during mate search.     

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     

Bi-directional sex change: testing the growth-rate advantage model

Bi-directional sex change in coral-dwelling fishes (genera Gobiodon and Paragobiodon) has been attributed to a growth-rate advantage for females during the non-breeding season. This model predicts that the smallest individual in a newly formed pair should always be female. To determine if a growth-rate advantage exists for female Gobiodon histrio, I monitored the growth of males and females in natural pairs during the breeding and non-breeding season. I then used a manipulative field experiment to test four predictions of the growth-rate advantage model: (1) the larger individual should change sex to male in new pairs containing two females; (2) the smaller individual should change sex to female in new pairs containing two males; (3) neither individual should change sex in heterosexual pairs where the male is larger than the female; and (4) both individuals should change sex in heterosexual pairs where the female is larger than the male. A growth-rate advantage was detected for female G. histrio during the non-breeding season; however, only the first three of the predicted outcomes were observed in the manipulative experiment. Sex change did not occur in heterosexual pairs where the female was larger than the male. Furthermore, growth did not differ between sex-changed and non-sex-changed fish; therefore, the absence of sex change in these pairs is not due to a growth cost to sex change. I propose that the risk of moving among spatially isolated habitat patches and the low probability of finding a mate have been more important than sex-specific differences in growth rates to the evolution of bi-directional sex change in coral-dwelling gobies.     

The presence of eggs in the nest and female choice in common freshwater gobies (Rhinogobius brunneus)

In many species of fishes with paternal care, females prefer to spawn with males who are already guarding eggs. We studied the effect of egg presence on female mate choice in common freshwater gobies, Rhinogobius brunneus sp. OR. In our tests, females did not prefer males with eggs, suggesting egg presence per se may not act as a cue to attract females. We also examined the effects of brood size on paternal care and offspring survival to look for possible benefits females could obtain when choosing males with eggs. Both fanning by egg-guarding males and egg survival increased with brood size. The presence of neighboring males did have a significantly negative effect on males' parental activity, which subsequently results in a lower level of egg survival than in solitary egg-guarding males. This result provides a partial explanation for the result of eggs not attracting females to mate.     

Association patterns of sailfin mollies (Poecilia latipinna): alternative hypotheses

Individuals may associate with each other due to a variety of selective forces, such as intra- and intersexual selection, and conspecific recognition. Previous studies have concluded that mate choice governs association behavior in polygynous species of fish. I examined whether mate choice underlies the preference for larger individuals by examining preference for association (time spent in proximity to a fish) not only between opposite-sex individuals but also between same-sex individuals of the live-bearing sailfin molly (Poecilia latipinna). Males and females from three size classes were tested with a large and a small object fish of the same and opposite sex. Females preferred to associate with larger over smaller males. Males also preferred to associate with larger over smaller females, as expected. The same female and male test fish also preferred to associate with larger over smaller fish of the same sex. Moreover, females demonstrated no significant difference in their strength of preference (large–small) when offered males or females. The same held true for males. When males and females were subsequently tested with one large male and one large female, females tended to prefer large males while males showed no significant preference for association based on sex. In another experiment, females were tested with a large female and a small male, and significantly preferred the former. These findings suggest that association patterns may have arisen under a variety of conditions, such as predation pressures, shoaling behavior, and associative preference behavior. The assumption that association behavior is a uniformly sufficient predictor of mate choice in fish needs to be re-examined for P. latipinna and other species. Received: 6 November 1998 / Received in revised form: 12 May 1999 / Accepted: 12 May 1999     

Congenital predispositions and early social experience determine the courtship patterns of males of the Amarillo fish

Mounting evidence indicates that learning shapes fish foraging and social behavior, which suggests that it may also underlie the frequently reported geographic variation in courtship. In this study, we analyzed how early social experience influences courtship patterns in males of the Amarillo fish (Girardinichthys multiradiatus). In a first experiment, we quantified the courtship of males from two allopatric populations grown in isolation and estimated the heritability of a key attribute of their courtship patterns. Then, we raised males from two allopatric populations with either sympatric or allopatric females and at two different densities, and registered their adult courtship patterns towards females from a third population. We found that the courtship pattern of males has a significant heritable component, yet in the second experiment, it was influenced by what type of females males were raised with, by their social rank (dominant/subordinate/singleton), and by the behavior of the female that they were courting. We conclude that courtship behavior in this fish has a congenital predisposition and is affected during development by different aspects of early experience and seemingly remains flexible throughout life; a complex ontogenetic trajectory that under natural conditions may have led to the locally stable dialect types observed in the courtship patterns of males from allopatric populations.     

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.     

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.     

Influence of male harassment and female competition on female feeding behaviour in a sexual–asexual mating complex of mollies (<Emphasis Type="Italic">Poecilia mexicana</Emphasis>, <Emphasis Type="Italic">P. formosa</Emphasis>)

Differential interests between the sexes regarding the number of copulations can result in sexual harassment. Hence, females may have less time available for foraging. Male sexual harassment often leads to fitness reduction in females. We used the mating complex of the bisexual fish Poecilia mexicana and the co-occurring all-female Poecilia formosa to study sexual harassment and its incurred cost on female feeding efficiency. P. formosa is a sperm-dependent parthenogen that requires mating with host males to induce embryogenesis, but the male genes are not used. We therefore predicted P. mexicana males to prefer conspecific females. Hence, costs of male sexual harassment should not occur in unisexuals. While P. formosa are at a disadvantage compared to P. mexicana females due to male mate choice (leading to sperm limitation), this could be traded-off by suffering less from sexual harassment. In our experiment, we found males to direct significantly more pre-copulatory mating behaviour towards conspecific females, whereas actual mating attempts did not differ between species. Contrary to our prediction, both types of females started feeding later and spent less time feeding in the presence of a male partner compared to the time spent feeding with another female, suggesting that females of both species suffer from male harassment. The focal females' feeding time declined with increasing body size of the female competitor, and the same pattern was found when a male was present. We discuss that—besides sexual harassment—other factors such as food competition and female mate choice may affect female feeding efficiency.     

"Cryptic" direct benefits of mate choice: choosy females experience reduced predation risk while in precopula

Despite the central role that female mate choice plays in the production of biological diversity, controversy remains concerning its evolution and maintenance. This is particularly true in systems where females are choosy but do not receive obvious direct benefits such as nuptial gifts that increase a female's survival and fecundity. In the absence of such direct benefits, indirect benefits (i.e., the production of superior offspring) are often invoked to explain the evolution of mate choice. However, females may receive less obvious, or "cryptic," direct benefits, particularly in species with prolonged pre-mating interactions (e.g., precopulatory mate guarding). We assessed the “cryptic” direct benefits of female choice for large male size in two species of freshwater amphipods that do not receive obvious direct benefits. Females paired with large males experienced decreased predation from fish. However, we found that the size of a female’s mate did not affect her predation risk against predatory dragonflies or the harassment she received by single males while paired. Our results demonstrate that even when females receive no traditional direct benefits, female choice for large male size can still provide important direct benefits. Such “cryptic” direct benefits may be common, especially in species with prolonged mating interactions, and are likely important for fully understanding the evolution of mate choice.     

Female European green lizards (Lacerta viridis) prefer males with high ultraviolet throat reflectance

The role of ultraviolet (UV) signals in intraspecific communication has been identified in a number of vertebrate taxa. In lizards, the signalling role of UV has only been shown in male–male competition and male mate choice. Here, we investigated whether male UV colour can be a basis of female association preference in European green lizards (Lacerta viridis), a species where males develop blue nuptial throat colouration with high UV reflectance. We experimentally manipulated the UV colour of male pairs, where the members of the pair did not differ significantly in body length, body weight, head size, throat UV chroma and brightness or throat blue chroma and brightness measured prior to colour manipulation. By providing these pairs of males to females (only visual stimuli could be perceived by the females), we assessed the role of UV in female association preference irrespective of other potentially important visual traits. We found that unmated but receptive females preferred males of higher UV reflectance. Our results show for the first time that UV colour can be an important male signal in female preference in reptiles.     

Correlational evidence of a sexually-selected handicap

Handicap models of sexual selection predict that ornaments must be costly to produce and/or to wear and maintain; only then can they evolve as reliable signals of genetic quality. We investigated in the laboratory one potential cost of possessing ornaments, using the viviparous fish Girardinichthys multiradiatus and its natural predator, the snake Thamnophis melanogaster. We found that female G. multiradiatus show preferences for males with larger fins, as measured from body correlates. Males with a morphology attractive to females, however, were more likely to be captured by snakes than were other males (Fig. 5). Greater vulnerability to snakes cannot be explained as a result of snake visual preferences, because snakes responded similarly to males and females (Fig. 6). Finally, males, particularly dominant ones, were more likely to inspect foraging snakes than were females (Fig. 7). We conclude that male Girardinichthys multiradiatus experience a sexually-selected handicap due to reduced mobility resulting from having enlarged fins.     

Ultraviolet reflectance influences female preference for colourful males in the European serin

Avian plumage colouration is one of the most impressive displays in nature and is frequently used as sexual signal. There is now considerable evidence that females consistently prefer males with the most elaborated colour displays. Bird colour vision expands into the ultraviolet (UV) range, which prompted several studies to test the importance of UV in mate choice, revealing that females are affected by the UV light component. These studies were mostly performed on structural plumage, whereas carotenoid-based plumage was rarely considered, although it also has a typical reflection peak in the UV. Our study tested the female choice over male yellow colouration, and whether it is influenced by UV removal, in the European serin (Serinus serinus), a sexually dichromatic cardueline finch, with males showing a conspicuous carotenoid-based yellow plumage. We shows that females preferred yellower males and that male attractiveness was lost when the UV colouration was blocked, with either of the UV-blocking techniques used. The results of our study indicate that the UV component of carotenoid colouration is important in the female mate assessment in serins and highlights the importance of considering colour perception in avian mate choice.