Male mice song syntax depends on social contexts and influences female preferences.

In 2005, Holy and Guo advanced the idea that male mice produce ultrasonic vocalizations (USV) with some features similar to courtship songs of songbirds. Since then, studies showed that male mice emit USV songs in different contexts (sexual and other) and possess a multisyllabic repertoire. Debate still exists for and against plasticity in their vocalizations. But the use of a multisyllabic repertoire can increase potential flexibility and information, in how elements are organized and recombined, namely syntax. In many bird species, modulating song syntax has ethological relevance for sexual behavior and mate preferences. In this study we exposed adult male mice to different social contexts and developed a new approach of analyzing their USVs based on songbird syntax analysis. We found that male mice modify their syntax, including specific sequences, length of sequence, repertoire composition, and spectral features, according to stimulus and social context. Males emit longer and simpler syllables and sequences when singing to females, but more complex syllables and sequences in response to fresh female urine. Playback experiments show that the females prefer the complex songs over the simpler ones. We propose the complex songs are to lure females in, whereas the directed simpler sequences are used for direct courtship. These results suggest that although mice have a much more limited ability of song modification, they could still be used as animal models for understanding some vocal communication features that songbirds are used for.

Female preferences based on male nutritional chemical traits

Selection favors females that attend to reliable information about male genetic quality and fitness. Male nutritional condition can be a significant sign of mate quality since poor nutrition can be related to reduced sperm quality, low sperm quantity, sexually transmitted diseases, and parasites. We tested whether female Nile tilapia, Oreochromis niloticus, preferred the chemical cues of males that were well fed with high-protein diet over those fed with low-protein diet. Females do not only discriminate between males but also show a preference for well-fed males, discriminating between the odors with respect to nutritional state, suggesting that they were responding to a food-specific chemical cue. It is therefore likely that nutritional condition is related to the production of pheromones in males. Our results suggest that information about male nutritional state can be conveyed in chemical cues and that females attend to these cues during mate choice.

The effect of diet and parasite load on female phonotaxis in the Texas field cricket, Gryllus integer

Female crickets respond selectively to variations in species-specific male calling songs. This selectivity has been shown to be age-dependent; older females are less choosy. However, female quality should also affect female selectivity. The effect of female quality on mate choice was examined in Gryllus integer by comparing the phonotactic responses of females on different diets and with different parasite loads to various synthetic models of conspecific calling song. Test females were virgin, 11-14 days old, and had been maintained on one of five diets varying in protein and fat content. Phonotaxis was quantified using a non-compensating Kugel treadmill which generates vector scores incorporating the speed and direction of movement of each female. Test females were presented with four calling song models which differed in pulse rate, but were still within the natural range of the species for the experimental temperature. After testing, females were dissected and the number of gregarine parasites within the digestive tract counted. There were no significant effects of either diet or parasitism on female motivation to mate although the combined effects of these variables seem to have an effect with no apparent trend. Control females did not discriminate among song types, but there was a trend of female preferences for lower pulse rates which are closest to the mean pulse rate for the species. Heavily parasitized females did not discriminate among pulse rates altho~gh there was a similar trend of high vector scores for low pulse rates. Diet, however, affected selectivity with poorly-fed females showing significantly high vector scores for pulse rates near the species mean. Such findings raise interesting questions about energy allocation and costs and risks of phonotaxis and mate choice in acoustic Orthoptera. These results are discussed in terms of sexual selection and female mate choice.

Developmental stress and female mate choice behaviour in the zebra finch

The potential effects of early environmental conditions on adult female mate choice have been largely neglected in studies of sexual selection. Our study tested whether developmental stress affects the mate choice behaviour of female zebra finches, Taeniopygia guttata, when choosing between potential mates. In an experiment manipulating developmental condition, female zebra finches were raised under nutritional stress or control conditions. In adulthood, female preferences were assessed using extensive four-stimulus mate choice trials. Nutritional stress affected growth rates during the period of stress, with experimentally stressed females lighter than controls. During mate choice trials stressed females were almost three times less active than controls and made fewer sampling visits to the stimulus males, although we found no evidence of a direct effect of developmental experience on which males were preferred. Thus, developmental experience had a clear effect on behavioural patterns in a mate choice context. To test whether this effect is specific to a mate choice context, we also investigated the effect of developmental stress on female activity rates in three social contexts: isolation, contact with a conspecific male (a potential mate) and contact with a conspecific female. Here, female activity did not differ between the experimental treatments in any of the social situations. Overall, our findings suggest that environmental conditions during early development can have long-term context-dependent consequences for adult female mate choice behaviour, mediated by changes in activity rates.

Homogamy preferences for cognitive sex-typicality in women

Homogamy has been suggested as crucial for human mate preferences and mate choice. People are attracted to and choose romantic partners that are similar to them in socio-demographic, physical, and psychological traits. However, only a few studies have shown homogamy in preferences for evolved sex-typical traits. Here, we have investigated male and female preferences for the level of cognitive masculinity-femininity (MF). We tested whether self-reported MF positively correlates with preferences for MF. One hundred men and one hundred women from Brazil filled in questionnaires on their own level of cognitive MF and preferred level of cognitive MF in their ideal partner. Half of the respondents were asked to indicate their preferences for long-term, and the other half for short-term relationships. We found a positive correlation between self-ascribed and preferred level of cognitive MF in women (P = 0.002), but no significant correlation in men (P = 0.309). There was no significant effect of the temporal context of the relationship, but there was a positive correlation between self-ascribed and preferred level of cognitive MF only in women answering about long-term partner. By subtracting the preferred from the selfascribed level of cognitive MF, we created a self-similarity index. We found that women desire potential mates more self-similar and more masculine than men (P < 0.001) and that in men there is greater variation in the self-similarity index than in women. Our results thus add to previous evidence on the role of homogamy in human mating, by showing preferences for self-similarity also in cognitive MF for women, especially for long-term partner preferences. Future studies should cross-culturally test whether the higher self-similar preference found in women is universal.

Female preference for male color is necessary and sufficient for assortative mating in 2 cichlid sister species

A critical step for speciation in the face of gene flow is the origination of reproductive isolation. The evolution of assortative mating greatly facilitates this process. Assortative mating can be mediated by one or multiple cues across an array of sensory modalities. We here explore possible cues that may underlie female mate choice in a sympatric species pair of cichlid fish from Lake Victoria, Pundamilia pundamilia and Pundamilia nyererei. Previous studies identified species-specific female preferences for male coloration, but effects of other cues could not be ruled out. Therefore, we assessed female choice in a series of experiments in which we manipulated visual (color) and chemical cues. We show that the visibility of differences in nuptial hue (i.e., either blue or red) between males of the 2 species is necessary and sufficient for assortative mating by female mate choice. Such assortment mediated by a single cue may evolve relatively quickly, but could make reproductive isolation vulnerable to environmental changes. These findings confirm the important role of female mate choice for male nuptial hue in promoting the explosive speciation of African haplochromine cichlids.

Inheritance of female mating preference in a sympatric sibling species pair of Lake Victoria cichlids: implications for speciation

Female mate choice has often been proposed to play an important role in cases of rapid speciation, in particular in the explosively evolved haplochromine cichlid species flocks of the Great Lakes of East Africa. Little, if anything, is known in cichlid radiations about the heritability of female mating preferences. Entirely sympatric distribution, large ecological overlap and conspicuous differences in male nuptial coloration, and female preferences for these, make the sister species Pundamilia pundamilia and P. nyererei from Lake Victoria an ideally suited species pair to test assumptions on the genetics of mating preferences made in models of sympatric speciation. Female mate choice is necessary and sufficient to maintain reproductive isolation between these species, and it is perhaps not unlikely therefore, that female mate choice has been important during speciation. A prerequisite for this, which had remained untested in African cichlid fish, is that variation in female mating preferences is heritable. We investigated mating preferences of females of these sister species and their hybrids to test this assumption of most sympatric speciation models, and to further test the assumption of some models of sympatric speciation by sexual selection that female preference is a single-gene trait. We find that the differences in female mating preferences between the sister species are heritable, possibly with quite high heritabilities, and that few but probably more than one genetic loci contribute to this behavioural speciation trait with no apparent dominance. We discuss these results in the light of speciation models and the debate about the explosive radiation of cichlid fishes in Lake Victoria.

The effect of male coloration on female mate choice in closely related Lake Victoria cichlids (Haplochromis nyererei complex)

We studied the effect of male coloration on interspeciÆc female mate choice in two closely related species of haplochromine cichlids from Lake Victoria. The species differ primarily in male coloration. Males of one species are red, those of the other are blue. We re- corded the behavioral responses of females to males of both species in paired male trials under white light and under monochromatic light, under which the interspecific differences in coloration were masked. Females of both species exhibited species-assortative mate choice when colour differences were visible, but chose non-assortatively when colour differences were masked by light conditions. Neither male behaviour nor overall female response frequencies differed between light treatments. That female preferences could be altered by manipulating the perceived colour pattern implies that the colour itself is used in interspecific mate choice, rather than other characters. Hence, male coloration in haplochromine cichlids does underlie sexual selection by direct mate choice, involving the capacity for individual assessment of potential mates by the female. Females of both species responded more frequently to blue males under monochromatic light. Blue males were larger and displayed more than red males. This implies a hierarchy of choice criteria. Females may use male display rates, size, or both when colour is unavailable. Where available, colour has gained dominance over other criteria. This may explain rapid speciation by sexual selection on male coloration, as proposed in a recent mathematical model.

Modeling the role of competition and cooperation in the evolution of katydid acoustic synchrony

The precise timing of individual signals in response to those of signaling neighbors is seen in many animal species. Synchrony is the most striking of the resultant timing patterns. One of the best examples of acoustic synchrony is in katydid choruses where males produce chirps with a high degree of temporal overlap. Cooperative hypotheses that speculate on the evolutionary origins of acousti synchrony include the preservation of the species-specific call pattern, reduced predation risks, and increased call intensity. An alternative suggestion is that synchrony evolved as an epiphenomenon of competition between males in response to a female preference for chirps that lead other chirps. Previous models investigating the evolutionary origins of synchrony focused only on intrasexual competitive interactions. We investigated both competitive and cooperative hypotheses for the evolution of synchrony in the katydid Mecopoda ``Chirper'' using physiologically and ecologically realistic simulation models incorporating the natural variation in call features, ecology, female preferences, and spacing patterns, specifically aggregation. We found that although a female preference for leading chirps enables synchronous males to have some selective advantage, it is the female preference for the increased intensity of aggregations of synchronous males that enables synchrony to evolve as an evolutionarily stable strategy.

Call intensity is a repeatable and dominant acoustic feature determining male call attractiveness in a field cricket

Acoustic signal variation and female preference for different signal components constitute the prerequisite framework to study the mechanisms of sexual selection that shape acoustic communication. Despite several studies of acoustic communication in crickets, information on both male calling song variation in the field and female preference in the same system is lacking for most species. Previous studies on acoustic signal variation either were carried out on populations maintained in the laboratory or did not investigate signal repeatability. We therefore used repeatability analysis to quantify variation in the spectral, temporal and amplitudinal characteristics of the male calling song of the field cricket Plebeiogryllus guttiventris in a wild population, at two temporal scales, within and across nights. Carrier frequency (CF) was the most repeatable character across nights, whereas chirp period (CP) had low repeatability across nights. We investigated whether female preferences were more likely to be based on features with high (CF) or low (CP) repeatability. Females showed no consistent preferences for CF but were significantly more attracted towards signals with short CPs. The attractiveness of lower CP calls disappeared, however, when traded off with sound pressure level (SPL). SPL was the only acoustic feature that was significantly positively correlated with male body size. Since relative SPL affects female phonotaxis strongly and can vary unpredictably based on male spacing, our results suggest that even strong female preferences for acoustic features may not necessarily translate into greater advantage for males possessing these features in the field. (C) 2013 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.

Attractive silences in cricket courtship song : mate choice using a short-range signal /

Matings systems using signals for sexual communication have been studied extensively and results commonly suggest that females use these signals for locating males, species-identification, and mate choice. Although numerous mating systems employ multiple signals, research has generally focused on long-range signals perhaps due to their prominence and ease of study. This study focused on the short-range acoustic courtship song of crickets. The results presented here suggest this signal is under selection by female choice. Females mated preferentially with males having shorter silences between the two types of ticks within the song. The length of these silences (Gap 1) was correlated with male condition such that males having long silences were significantly lower in mass with respect to body size when compared to males having short silences. Both Gap 1 length and male condition were significantly repeatable within males over time suggesting the possibility these traits have a genetic basis. This study is the first empirical study to test female preferences within the natural variation of the courtship song. It now appears, at least in crickets, that both the longand short-range signals of a multi-signal mating system may contribute to male mating success.

Ultraviolet vision, fluorescence and mate choice in a parrot, the budgerigar Melopsittacus undulatus

As in many parrots, the plumage of the budgerigar Melopsittacus undulatus reflects near-ultraviolet (UVA) wavelengths (300-400 nm) and exhibits UVA-induced fluorescence. However, there have, to our knowledge, been no tests of whether the yellow fluorescence observed under intense UVA illumination has any role in signalling. Four experiments were carried out on wild-type budgerigars, where the presence and absence of UV reflectance and fluorescence were manipulated using filters. Few studies have attempted to separate the contribution of UV reflectance to plumage hue as opposed to brightness or distinguish between a role in sexual as opposed to social preferences. However, our first experiments show that not only do females consistently prefer UV-reflecting males, but also that the observed preferences are due to removal of UV affecting the perceived hue rather than brightness. Furthermore, we found no effect Of the light environment on male response to females, suggesting that the female preferences relate to plumage colour per se. Whilst UV reflectance appears important in heterosexual choice by, females, it has no detectable influence on same-sex association preferences. The results from the second series of experiments suggest that enhancement of the budgerigar's yellow coloration through fluorescence has no effect on male attractiveness. However, the fluorescent plumage may play a role in signalling by virtue of the fact that it absorbs UVA and so increases contrast with nearby UV-reflecting plumage. Our study provides convincing evidence that UV reflectances can play a role in mate choice in non-passerines, but no evidence that the yellow fluorescence observed under UVA illumination is itself important as a signal.