Nonmating Contexts Research Articles

Mimicry in Mating: An Analysis of Postural Mirroring in Mating and Non-Mating Contexts [Conference Presentation Abstract

Mimicry in Mating: An Analysis of Postural Mirroring in Mating and Non-Mating Contexts [Conference Presentation Abstract

Substrate colour guides turquoise killifish's (Nothobranchius furzeri) choice of preferred spawning habitat.

Turquoise killifish (Nothobranchius furzeri) is a promising new model species used in biomedical and ecological laboratory experiments, and should be kept under optimal conditions to ensure fish welfare and the quality of science. While the popularity of this model species is rapidly increasing, we need to improve our understanding of how the species interacts with its environment in order to optimise its husbandry. Specifically, turquoise killifish are substrate spawners that bury their eggs in the sediment which can be accommodated under captive conditions, but it is not yet known whether or not turquoise killifish have a preference for a specific sediment colour. Here, we performed a laboratory experiment in which fish could choose between white, orange, and black sand for spawning, colours of which are relevant in both laboratory and field conditions. We assessed their preference in the context of single breeding pairs, as well as in a social group setting. Additionally, we also assessed preference of individuals for a white vs. black background in a non-mating context. Single breeding pairs deposited over 3.5× more eggs in black compared to orange or white sand. Similarly, fish in social groups deposited over 3.5× more eggs in black compared to orange sand, which in turn was over 2× times higher than that in white sand. Fish showed a slight preference for the black compared to the white zone in a non-mating context but this did not correlate with substrate choice during the spawning tests. The results suggest that turquoise killifish select their preferred spawning location based on the colour of the substrate. These findings contribute to our understanding of the species' biology and can help to guide good welfare and scientific practice. This article is protected by copyright. All rights reserved.

A ROLE FOR RECEIVER BIAS IN ROSE BITTERLING MATE CHOICE?

The evolution of costly secondary sex traits in males may arise as a result of male-male competition or female mate choice. Female mating decisions may be associated with either direct or indirect benefits, and may evolve as a consequence of selection for signal detection in a non-mating context. We raised fish in the laboratory fed only on green coloured food and subsequently tested their foraging preferences by presenting them with plastic strips of different colours and recording the number of bites directed at each. We conducted separate tests on juveniles and sexually mature fish, and compared the responses of males and females. Male rose bitterling (Rhodeus ocellatus) display red, carotenoid-based nuptial colouration but its function in the mating system is unclear; there is little evidence that male colour plays a role in female mating decisions although there is a weak relationship between colour and dominance among males. We tested for a bias towards red in a non-mating context and found that bitterling show a strong response to red food items, irrespective of age, sex or prior experience. This correlation between a sexually selected trait and an intrinsic attraction to red appears to support the receiver bias hypothesis for the evolution of red nuptial colouration in bitterling. We discuss how this trait could be maintained under sexual selection in the absence of strong preference or any obvious fitness benefits.

Female preference for color-enhanced males: a test of the sensory bias model in medaka, a drab fish

Abstract Sexual selection research has long focused on the evolution of female mate preferences. Most of the models that have been developed posit that mate preferences evolve in a mating context. In contrast, the sensory bias model proposes that mate choice preferences arise in a non-mating context, as a by-product of natural selection acting on a female’s perceptual system. Recent research has shown that many species of fishes, from across a large clade including poeciliids, goodeids, and medaka, have a bias for long wavelength (LW) colors (yellow, orange, red) in a non-mating context. Even species that do not have LW-colored ornaments, apparently because they have been lost secondarily, retain this latent bias for LW colors. Here, we predicted that female Oryzias latipes (Japanese medaka), a drab species with a latent preference for LW colors, would show a mate choice preference for males with an artificial secondary sexual trait—a colored stripe added to their flank. We confirmed that females were more responsive to red and orange objects in a non-mating context than to other colors. We also showed that females were less resistant towards males with an LW-colored stripe than to those enhanced with a non-LW stripe and that, for many females, responses towards specific LW colors were consistent across these non-mating and mating contexts. Therefore, our results provide support for the sensory bias model by providing a link between a sensory bias in a non-mating context and a mate choice preference in a drab species like medaka.

Aggression, glucocorticoids, and the chronic costs of status competition for wild male chimpanzees

Across vertebrates, high social status affords preferential access to resources, and is expected to correlate positively with health and longevity. Increasing evidence, however, suggests that although dominant females generally enjoy reduced exposure to physiological and psychosocial stressors, dominant males do not. Here we test the hypothesis that costly mating competition by high-ranking males results in chronic, potentially harmful elevations in glucocorticoid production. We examined urinary glucocorticoids (n = 8029 samples) in a 20-year longitudinal study of wild male chimpanzees (n = 20 adults) in the Kanyawara community of Kibale National Park, Uganda. We tested whether glucocorticoid production was associated with dominance rank in the long term, and with mating competition and dominance instability in the short term. Using mixed models, we found that both male aggression and glucocorticoid excretion increased when the dominance hierarchy was unstable, and when parous females were sexually available. Glucocorticoid excretion was positively associated with male rank in stable and unstable hierarchies, and in mating and non-mating contexts. Glucorticoids increased with both giving and receiving aggression, but giving aggression was the primary mechanism linking elevated glucocorticoids with high rank. Glucocorticoids also increased with age. Together these results show that investment in male-male competition increases cumulative exposure to glucocorticoids, suggesting a long-term tradeoff with health that may constrain the ability to maintain high status across the life course. Our data suggest that the relationship between social rank and glucocorticoid production often differs in males and females owing to sex differences in the operation of sexual selection.

Mating Preference for Novel Phenotypes Can Be Explained by General Neophilia in Female Guppies.

AbstractUnderstanding how genetic variation is maintained in ecologically important traits is a fundamental question in evolutionary biology. Male Trinidadian guppies (Poecilia reticulata) exhibit extreme genetic diversity in color patterns within populations, which is believed to be promoted by a female mating preference for rare or novel patterns. However, the origins of this preference remain unclear. Here, we test the hypothesis that mating preference for novel phenotypes is a by-product of general neophilia that evolved in response to selection in nonmating contexts. We measured among-female variation in preference for eight different, novel stimuli that spanned four ecological contexts: mate choice, exploration, foraging, and social (but nonsexual) interactions. Females exhibited preference for novelty in six out of eight tests. Individual variation in preference for novelty was positively correlated among all eight types of stimuli. Furthermore, factor analysis revealed a single axis of general neophilia that accounts for 61% of individual variation in preference for novel color patterns. The single-factor structure of neophilia suggests that interest in novelty is governed primarily by shared processes that transcend context. Because neophilia likely has a sizable heritable component, our results provide evidence that mating preference for novel phenotypes may be a nonadaptive by-product of natural selection on neophilia.

Alternative reproductive tactics shape within-species variation in behavioral syndromes

AbstractMultiple behaviors can correlate with each other at the individual level (behavioral syndrome), and behavioral syndromes can vary in their direction between populations within a species. Within-species variation in behavioral syndromes is predicted to be associated with alternative reproductive tactics (ARTs), which evolve under different selection regimes. Here, we tested this using a water strider species, Gerris gracilicornis, in which males employ 2 ARTs that are fixed for life: signaling males (producing courtship ripples) versus nonsignaling males (producing no courtship ripples). We measured multiple behaviors in males with both of these ARTs and compared behavioral syndromes between them. Our results showed that signaling males were more active and attempted to mate more frequently than nonsignaling males. This shaped an overall behavioral syndrome between activities in mating and nonmating contexts when we pooled both ARTs. In addition, the behavioral syndromes between cautiousness and mating activity differed significantly between ARTs. In signaling males, the syndrome was significantly negative: signaling males more eager to mate tended to leave their refuges more rapidly. However, mating activity and cautiousness were not correlated in nonsignaling males. This might be because active males, in the context of predation risk and mating, were favored during the evolution and maintenance of the unique intimidating courtship tactic of G. gracilicornis males. Thus, our findings suggest that ARTs facilitate behavioral divergence and also contribute to the evolution of tactic-specific behavioral syndromes. We also show that research on ARTs and behavioral syndromes can be harmonized to study behavioral variation.

Smelling is Telling: Human Olfactory Cues Influence Social Judgments in Semi-Realistic Interactions.

How does a person's smell affect others' impressions of them? Most body odor research asks perceivers to make social judgments based on armpit sweat without perfume or deodorant, presented on t-shirts. Yet, in real life, perceivers encounter fragranced body odor, on whole bodies. Our "raters" wore blindfolds and earplugs and repeatedly smelled same-sex "donors" in live interactions. In one condition, donors wore their normal deodorant and perfume ("diplomatic" odor) while in the other condition, donors were asked to avoid all outside fragrance influences ("natural" odor). We assessed the reliability of social judgments based on such live interactions, and the relationships between live judgments and traditional t-shirt based judgments, and between natural- and diplomatic odor-based judgments. Raters' repeated live social judgments (e.g., friendliness, likeability) were highly consistent for both diplomatic and natural odor, and converged with judgments based on t-shirts. However, social judgments based on natural odor did not consistently predict social judgments based on diplomatic odor, suggesting that natural and diplomatic body odor may convey different types of social information. Our results provide evidence that individuals can perceive reliable, meaningful social olfactory signals from whole bodies, at social distances, regardless of the presence or absence of perfume. Importantly, however, the social value of these signals is modified by the addition of exogenous fragrances. Further, our focus on judgments in same-sex dyads suggests that these olfactory cues hold social value in non-mating contexts. We suggest that future research employ more ecologically relevant methods.

Why do ovigerous females approach courting males? Female preferences and sensory biases in a fiddler crab.

Perceptual biases explain the origin and evolution of female preference in many species. Some responses that mediate mate choice, however, may have never been used in nonmating contexts. In the fiddler crab, Uca mjoebergi, mate‐searching females prefer faster wave rates and leading wave; however, it remains unclear whether such responses evolved in a mating context (i.e., the preference has effect on the fitness of the female and her offspring that arise from mating with a particular male) or a nonmating contexts (i.e., a female obtains direct benefits through selecting the male with a more detectable trait). Here, we compared the preferences of mate‐searching with those of ovigerous females that are searching for a burrow and do not concern about male “quality.” Results showed that as both mate‐searching and ovigerous females preferentially approached robotic males with faster wave rates. This suggests that wave rate increases detectability/locatability of males, but the mating preference for this trait is unlikely to evolve in the mating context (although it may currently function in mate choice), as it does not provide fitness‐related benefit to females or her offspring. Wave leadership, in contract, was attractive to mate‐searching females, but not ovigerous females, suggesting that female preference for leadership evolves because wave leadership conveys information about male quality. We provide not only an empirical evidence of sensory biases (in terms of the preference for faster wave), but the first experimental evidence that mating context can be the only selection force that mediates the evolution of male sexual traits and female preference (in terms of the preference for leading wave).

Intimidating courtship and sex differences in predation risk lead to sex-specific behavioural syndromes

Behavioural correlations between mating behaviour and antipredator behaviour are expected when sexual behaviour increases predation risk. However, the correlation would be different between males and females, particularly when the sexes experience different levels of predation risk. Here, we tested this idea using a water strider species, Gerris gracilicornis (Heteroptera: Gerridae). G. gracilicornis males employ an unusual intimidating courtship strategy capitalizing on predator behaviours and female response to predators. Since mounted females are more vulnerable than males to predatory attacks from below, we predicted that changes in female mating behaviours across predation contexts (boldness in a mating context) should be associated with female antipredator behaviours (boldness in a nonmating context), but that the correlation would be weaker for male mating behaviours. In a series of behavioural assays, we measured water striders' (1) mating behaviour in the absence of predators, (2) mating behaviour in the presence of predation risk, (3) boldness in the mating context (changes in female mating behaviour after predator attacks) and (4) boldness in the nonmating context. We found that females behaved more cautiously around predators in both the mating and nonmating contexts. We also found that females' boldness in the mating context was significantly correlated with their boldness in the nonmating context. In contrast to females, antipredator behaviour of males in the nonmating context did not correlate with their boldness in the mating context. Thus we suggest that sex differences in boldness across predation contexts appear to cause sex-specific behavioural syndromes.

Selflessness is sexy: reported helping behaviour increases desirability of men and women as long-term sexual partners

BackgroundDespite its short-term costs, behaviour that appears altruistic can increase an individual’s inclusive fitness by earning direct (selfish) and/or indirect (kin-selected) benefits. An evolved preference for other-regarding or helping behaviour in potential mates has been proposed as an additional mechanism by which these behaviours can yield direct fitness benefits in humans.ResultsWe asked 32 heterosexual women and 35 heterosexual men to rate the attractiveness of members of the opposite sex in the presence and the absence of information about helping behaviours. Reports of helping behaviour were associated with a significant increase in the attractiveness of both men and women as potential long-term sexual partners. Altruism also increased the attractiveness of men as potential partners for short-term flings, but to a lesser extent than when the same men were being considered for long-term relationships. Altruism did not affect the attractiveness of women as partners for short-term flings.ConclusionsOur results unite two important areas of evolutionary theory – social evolution and sexual selection – and extend the list of means by which helping behaviours, which appear at first glance to be costly to the actor, can in fact earn direct fitness benefits. Helping behaviours may be attractive because they signal ‘good genes’ and/or because they are perceived as a signal of likely provision of non-genetic benefits (e.g. parental care). Exactly why helping behaviours in a non-mating context might be attractive to potential mates, and whether they are honest signals of mate quality, remains to be elucidated.

Firefly flashing and jumping spider predation

Bioluminescent flashing in fireflies, while primarily a sexual signal, is known to deter some predators while attracting others. We tested whether flashing serves an antipredator function against two species of diurnal, visually hunting jumping spiders, Phidippus princeps and Phidippus audax. To confirm anecdotal reports that fireflies flash during the day in a nonmating context, we documented that adult fireflies (Photuris sp.) of both sexes flash when disturbed in daylight. We also confirmed that activity periods of Phidippus and fireflies overlap, and that spiders attack fireflies and elicit flashing behaviour. We conducted three experiments to examine the influence of flashing on spider behaviour. (1) We tested whether the sudden onset of a flashing LED startled spiders that had initiated attacks on crickets, and found no evidence that it did so. (2) We used choice tests to determine whether flashing lights attracted or deterred spiders from attacking palatable prey. Spiders more often attacked crickets positioned next to a flashing LED versus an LED that was either off or glowed steadily. (3) Many firefly species are distasteful. Therefore, we tested whether flashing lights facilitate avoidance of unpalatable prey with experience. Spiders were given seven encounters with unpalatable prey (nonluminescent Ellychnia corrusca fireflies) associated with either flashing or unlit LEDs. Spiders in the two treatments were equally likely to attack the prey during their first encounter, but spiders exposed to flashing LEDs were significantly less likely to attack unpalatable prey by their seventh trial. Spiders tested with palatable prey showed no decline in attacks after exposure to flashing LEDs. We conclude that, although bioluminescent flash signals may increase attack rates by predatory jumping spiders, they may also facilitate learning about unpalatable prey. Thus, the costs and benefits of flashing may depend on the prevalence of firefly palatability.

Line-following preferences of male crab spiders, Misumena vatia

Male crab spiders locate cryptic females by methods that have proved elusive to researchers. Previous work has suggested that female draglines provide males with clues to the presence of females. Unlike other wandering spiders, however, M. vatia do not deposit mate-attracting pheromones on their draglines. Based on evidence that the size and strength of draglines vary predictably with the age and sex of the source spider, we tested the hypothesis that mechanical cues allow males to identify the age, sex and species of the dragline producer. We ran adult and penultimate male crab spiders through a series of trials to identify preferences for following different types of dragline. A spider's developmental stage influenced its response to draglines of other individuals, suggesting that these responses were influenced by the search for mates. Adult males preferred adult and juvenile female draglines and selected conspecific adult female draglines over draglines from adult females of a related species. Penultimate males did not show significant preferences in these tests. Mechanical cues may therefore moderate the responses of the adult males to foreign draglines. We consider dragline following in M. vatia as a model of how cues produced in a nonmating context may facilitate mate search, and we suggest that study of such species-specific environmental modifications may shed insight into the evolution of mate location systems.

Carotenoid availability affects the development of a colour-based mate preference and the sensory bias to which it is genetically linked

Regardless of their origins, mate preferences should, in theory, be shaped by their benefits in a mating context. Here we show that the female preference for carotenoid colouration in guppies (Poecilia reticulata) exhibits a phenotypically plastic response to carotenoid availability, confirming a key prediction of sexual selection theory. Earlier work indicated that this mate preference is genetically linked to, and may be derived from, a sensory bias that occurs in both sexes: attraction to orange objects. The original function of this sensory bias is unknown, but it may help guppies find orange-coloured fruits in the rainforest streams of Trinidad. We show that the sensory bias also exhibits a phenotypically plastic response to carotenoid availability, but only in females. The sex-specificity of this reaction norm argues against the hypothesis that it evolved in a foraging context. We infer instead that the sensory bias has been modified as a correlated effect of selection on the mate preference. These results provide a new type of support for the hypothesis that mate preferences for sexual characters evolve in response to the benefits of mate choice--the alternatives being that such preferences evolve entirely in a non-mating context or in response to the costs of mating.