Variations in Mating and Reproduction in Oriental Fruit Moth Caused by Adult Physiological State in Laboratory Tests.

Grapholita molesta (Busck) is a pest of rosaceous fruit plants worldwide. Due to a combination of monandry and promiscuity in G. molesta, the age and mating history of both sexes significantly affected the mating and reproductive success. In this study, the interactions of different ages (3, 5, or 7 days) and mating history (unmated or mated) in each sex on the mating selection, reproductive system, and offspring production were investigated in the laboratory. The results showed that these differences mainly occurred in young females or males, associated with unmated or mated state. Especially, the 3-day-old unmated females were preferred by the 7-day-old males but discriminated against by the 3- or 5-day-old unmated males, whereas the 3-day-old mated males were preferred by the 3-day-old mated or 7-day-old females but discriminated against by the 3- or 5-day-old unmated females. The lengths of the ovarian ducts were affected by age in the unmated females, with the greatest length being found at 7 days old. The size of testes varied with age in the unmated males, being the largest at 3 days old. At 3 days old, the testes size of the unmated males was larger than that of the mated males. The pairing of 5-day-old unmated females × 3-day-old mated males maximized the successful matings. The least productive pairing was 7-day-old unmated females × 5-day-old mated males. The pairing of 5-day-old mated males × 3-day-old mated females had the lowest number of matings and the highest number of offspring. The pairing of 3-day-old mated females × 3-day-old mated males had a high rate of mating success and the most offspring. These results revealed the different roles between females and males because of physiological states in terms of the reproductive biology in G. molesta.

Social Plasticity Enhances Signal-Preference Codivergence.

AbstractThe social environment is often the most dynamic and fitness-relevant environment animals experience. Here we tested whether plasticity arising from variation in social environments can promote signal-preference divergence-a key prediction of recent speciation theory but one that has proven difficult to test in natural systems. Interactions in mixed social aggregations could reduce, create, or enhance signal-preference differences. In the latter case, social plasticity could establish or increase assortative mating. We tested this by rearing two recently diverged species of Enchenopa treehoppers-sap-feeding insects that communicate with plant-borne vibrational signals-in treatments consisting of mixed-species versus own-species aggregations. Social experience with heterospecifics (in the mixed-species treatment) resulted in enhanced signal-preference species differences. For one of the two species, we tested but found no differences in the plastic response between sympatric and allopatric sites, suggesting the absence of reinforcement in the signals and preferences and their plastic response. Our results support the hypothesis that social plasticity can create or enhance signal-preference differences and that this might occur in the absence of long-term selection against hybridization on plastic responses themselves. Such social plasticity may facilitate rapid bursts of diversification.

Effect of light bias on male mating signal and female mate choice in a sexually dimorphic Amazon fish.

Colourful signals are usually honest indicators of mate quality since they are energetically costly. However, how colours are perceived by choosers is highly affected by the environmental light condition. Amazon black waters are strongly red-biased while clear waters show no apparent colour bias. The sailfin tetra Crenuchus spilurus is a sexually dimorphic Amazon fish species; males have hyperallometric dorsal and anal fins conspicuously ornamented with red and yellow markings. The species has two main lineages, which inhabit black and clear waters. A comparison of the red colouration of the ornaments of males from different lineages indicates that red bias increases the perceived intensity of red colouration but decreases the perceived among-individual variation in red colour. In mate choice experiments, females from all lineages preferred males with larger ornaments. Clear water lineage females were more likely to accept males under red-biased lighting, which increases the apparent red colouration, suggesting the importance of the red colouration in their mate choice. On the other hand, male acceptance by females from black waters did not change under different light conditions, suggesting that signals other than the red colouration (e.g. size of ornaments) were more important in their mate choice.

CD-1 mice females recognize male reproductive success via volatile organic compounds in urine.

Sexual selection is considered as one of the leading factors of evolutionary development. In the conditions of incessant competition, specialized methods of attracting individuals of the opposite sex as well as criteria for assessing the quality of a sexual partner have been formed. In order for animals to rely on signaling from sexual partners, the signal must reflect the morpho-physiological status of animals. A high reproductive efficiency of male mice is a good advantage for mate selection and thus must be somehow demonstrated to potential mates. The aim of our study was to find out if male mice could demonstrate their reproductive efficiency through urine volatile organic compounds. The experiment implies cohabiting one male with two mature females for 6 days. The reproductive success of the male was assessed by the presence or absence of pregnant females. At the same time, naive females, who did not participate in reproduction, assessed the urine of the successful males as more attractive, which was expressed in shorter Latency time of sniffs in the Olfactory test. Using a rapid headspace GC/MS analysis, we have found volatile organic compounds (VOCs) in male urine that correlated with female behavior. It turned out that these substances are derivatives of mouse pheromone 6-hydroxy-6-methyl-3-heptanone. The amplitude of peaks corresponding to this pheromone correlated with the testosterone level in blood and the weight of preputial glands. The amplitude of peaks increased in males after mating with whom the females turned out to be pregnant. It is important to note that body weight, weight of testes, weight of seminal vesicles, weight of preputial glands, and plasma testosterone level alone are not reliable indicators of male reproductive success. Thus, the content of the pheromone 6-hydroxy-6-methyl-3-heptanone in the urine of males can serve as a good predictor of the quality of the male as a sexual partner for female CD-1 mice.

The effect of individual state on the strength of mate choice in females and males.

Animals are thought to gain significant fitness benefits from choosing high-quality or compatible mates. However, there is large within-species variation in how choosy individuals are during mating. This may be because the costs and benefits of being choosy vary according to an individual's state. To test this, I systematically searched for published data relating the strength of animal mate choice in both sexes to individual age, attractiveness, body size, physical condition, mating status, and parasite load. I performed a meta-analysis of 108 studies and 78 animal species to quantify how the strength of mate choice varies according to individual state. In line with the predictions of sexual selection theory, I find that females are significantly choosier when they are large and have a low parasite load, thus supporting the premise that the expression of female mate choice is dependent on the costs and benefits of being choosy. However, female choice was not influenced by female age, attractiveness, physical condition, or mating status. Attractive males were significantly choosier than unattractive males, but male mate choice was not influenced by male age, body size, physical condition, mating status, or parasite load. However, this dataset was limited by a small sample size, and the overall correlation between individual state and the strength of mate choice was similar for both sexes. Nevertheless, in both males and females individual state explained only a small amount of variation in the strength of mate choice.

Male mating choices: The drive behind menopause?

When we examine the life history of humans against our closest primate relatives, the other great apes, there is notably a greater longevity in humans which includes a distinctive postmenopausal life stage, leading to the question, "How did human females evolve to have old-age infertility?" In their paper "Mate choice and the origin of menopause" (Morton et al., 2013), Morton et al. developed an agent-based model (ABM) to investigate the novel hypothesis that ancestral male mating choices, particularly forgoing mating with older females, were the driving force behind the evolution of menopause. From their model, they concluded that indeed male preference for young female mates could have driven females to lose fertility at older ages through deleterious mutations, leading to menopause. In this work, we revisit their male-mate-choice hypothesis by formulating an analogous mathematical model using a system of ordinary differential equations (ODEs). We first show that our ODE model recreates the qualitative behaviour and hence conclusions of key scenarios in Morton et al. (2013). However, since our ODE system is less computationally demanding than their ABM, we also conduct a broader sensitivity analysis over a range of parameters and differing initial conditions to analyse the dependence on their conclusions to underlying assumptions. Our results challenge those of Morton et al. as we find that even the slightest deviation from an exclusive mating preference for younger females would counteract the evolution of menopause. Consequently, we propose that their male-mate-choice hypothesis is incomplete and needs further explanation of how a male strategy to exclusively mate with young females could have arisen in our common ancestors and remained evolutionarily stable for long enough to drive the evolution of old-age female infertility.

Strong spatial population structure shapes the temporal coevolutionary dynamics of costly female preference and male display.

Female mating preferences for exaggerated male display traits are commonplace. Yet, comprehensive understanding of the evolution and persistence of costly female preference through indirect (Fisherian) selection in finite populations requires some explanation for the persistence of additive genetic variance (Va ) underlying sexual traits, given that directional preference is expected to deplete Va in display and hence halt preference evolution. However, the degree to which Va , and hence preference-display coevolution, may be prolonged by spatially variable sexual selection arising solely from limited gene flow and genetic drift within spatially structured populations has not been examined. Our genetically and spatially explicit model shows that spatial population structure arising in an ecologically homogeneous environment can facilitate evolution and long-term persistence of costly preference given small subpopulations and low dispersal probabilities. Here, genetic drift initially creates spatial variation in female preference, leading to persistence of Va in display through "migration-bias" of genotypes maladapted to emerging local sexual selection, thus fueling coevolution of costly preference and display. However, costs of sexual selection increased the probability of subpopulation extinction, limiting persistence of high preference-display genotypes. Understanding long-term dynamics of sexual selection systems therefore requires joint consideration of coevolution of sexual traits and metapopulation dynamics.

Male Mating Expectations in Brazilian and American Samples.

This study aims to investigate assortative mating based on mate value from male perspective. Male participants (132 Brazilian and 106 American) evaluated hypothetical "stimulus" males described in terms of physical attractiveness, social skills, and social status (each varied in high or low levels). Participants rated each stimulus and each stimulus' preferred mating partner on nine traits. The results showed that (1) positive assortative mating was expected in romantic relationships; (2) the stimulus ratings did not vary independently, suggesting that mate value is the result of the interaction of the characteristics of individuals; and (3) that participants expected physically attractive and healthier female partners to pair with high-status male stimuli. The American and Brazilian mating expectations were similar, minor differences indicate that Brazilian participants considered men with high levels of social skills to be more ambitious and intelligent; American participants expected men of high status to be healthier; Brazilians expect men of high status to have more attractive faces, while Americans expected these men to possess more attractive bodies; and Brazilian participants assigned more attractive bodies to men of lower status. These differences reflect the influence of economic and cultural factors on the local environment. The study contributes to the understanding of the construction of market value and reveals that male expectations are in line with human mating preferences. The investigation of mating expectations can be a rich approach to investigate socio-cultural aspects that are related to mating in different cultures.

Reproductive interference and sensitivity to female pheromones in males and females of two herbivorous mite species.

Competitive interaction between sister species can be affected by reproductive interference (RI) depending on the ability of males to discriminate conspecific from heterospecific mates. We study such interactions in Tetranychus evansi and T. urticae. These spider mites co-occur on solanaceous plants in Southern Europe, and cause important yield losses in tomato crops. Previous studies using Spanish populations found that T. evansi outcompetes T. urticae, and that this is due to unidirectional RI of T. evansi males with T. urticae females. The unidirectional RI is attributed to differences in male mate preference for conspecific females between the two species. Also, differences in the propensity of interspecific web sharing in females plays a role. To investigate proximate mechanisms of this RI, here we study the role of female pheromones on male mate preference and female web sharing. We extracted pheromones from females of the two species, and investigated if males and females were arrested by the pheromone extractions in various concentrations. We observed that T. urticae males were more sensitive to the pheromone extractions and able to discriminate conspecific from heterospecific ones. Tetranychus evansi males, on the other hand, were less sensitive. Females from both species were arrested by conspecific pheromone extraction in lower concentrations. In conclusion, heterospecific mating by T. evansi males, which results in RI, can be explained by their lack of discrimination between female pheromones of the two species. Differences in the propensity of interspecific web sharing in females might not be explained by the pheromones that we investigated.

Designing mate choice experiments.

The important role that mate choice plays in the lives of animals is matched by the large and active research field dedicated to studying it. Researchers work on a wide range of species and behaviours, and so the experimental approaches used to measure animal mate choice are highly variable. Importantly, these differences are often not purely cosmetic; they can strongly influence the measurement of choice, for example by varying the behaviour of animals during tests, the aspects of choice actually measured, and statistical power. Consideration of these effects are important when comparing results among studies using different types of test, or when using laboratory results to predict animal behaviour in  natural populations. However, these effects have been underappreciated by the mate choice literature to date. I focus on five key experimental considerations that may influence choice: (i) should mating be allowed to occur, or should a proxy behavioural measure of preference be used instead? (ii) Should subjects be given a choice of options? (iii) Should each subject be tested more than once, either with the same or different stimuli? (iv) When given a choice, how many options should the subject choose between? (v) What form should the experimental stimuli take? I discuss the practical advantages and disadvantages of common experimental approaches, and how they may influence the measurement of mate choice in systematic ways. Different approaches often influence the ability of animals to perceive and compare stimuli presented during tests, or the perceived costs and benefits of being choosy. Given that variation in the design of mate choice experiments is likely unavoidable, I emphasise that there is no single 'correct' approach to measuring choice across species, although ecological relevance is crucial if the aim is to understand how choice acts in natural populations. I also highlight the need for quantitative estimates of the sizes of potentially important effects, without which we cannot make informed design decisions.

The Circadian Clock Improves Fitness in the Fruit Fly, Drosophila melanogaster.

It is assumed that a properly timed circadian clock enhances fitness, but only few studies have truly demonstrated this in animals. We raised each of the three classical Drosophila period mutants for >50 generations in the laboratory in competition with wildtype flies. The populations were either kept under a conventional 24-h day or under cycles that matched the mutant's natural cycle, i.e., a 19-h day in the case of per s mutants and a 29-h day for per l mutants. The arrhythmic per 0 mutants were grown together with wildtype flies under constant light that renders wildtype flies similar arrhythmic as the mutants. In addition, the mutants had to compete with wildtype flies for two summers in two consecutive years under outdoor conditions. We found that wildtype flies quickly outcompeted the mutant flies under the 24-h laboratory day and under outdoor conditions, but per l mutants persisted and even outnumbered the wildtype flies under the 29-h day in the laboratory. In contrast, per s and per 0 mutants did not win against wildtype flies under the 19-h day and constant light, respectively. Our results demonstrate that wildtype flies have a clear fitness advantage in terms of fertility and offspring survival over the period mutants and - as revealed for per l mutants - this advantage appears maximal when the endogenous period resonates with the period of the environment. However, the experiments indicate that per l and per s persist at low frequencies in the population even under the 24-h day. This may be a consequence of a certain mating preference of wildtype and heterozygous females for mutant males and time differences in activity patterns between wildtype and mutants.

Genetic coupling of signal and preference facilitates sexual isolation during rapid speciation.

The divergence of sexual signals is ultimately a coevolutionary process: while signals and preferences diverge between lineages, they must remain coordinated within lineages for matings to occur. Divergence in sexual signals makes a major contribution to evolving species barriers. Therefore, the genetic architecture underlying signal-preference coevolution is essential to understanding speciation but remains largely unknown. In Laupala crickets where male song pulse rate and female pulse rate preferences have coevolved repeatedly and rapidly, we tested two contrasting hypotheses for the genetic architecture underlying signal-preference coevolution: linkage disequilibrium between unlinked loci and genetic coupling (linkage disequilibrium resulting from pleiotropy of a shared locus or tight physical linkage). Through selective introgression and quantitative trait locus (QTL) fine mapping, we estimated the location of QTL underlying interspecific variation in both female preference and male pulse rate from the same mapping populations. Remarkably, map estimates of the pulse rate and preference loci are as close as 0.06 cM apart, the strongest evidence to date for genetic coupling between signal and preference loci. As the second pair of colocalizing signal and preference loci in the Laupala genome, our finding supports an intriguing pattern, pointing to a major role for genetic coupling in the quantitative evolution of a reproductive barrier and rapid speciation in Laupala. Owing to its effect on suppressing recombination, a coupled, quantitative genetic architecture offers a powerful and parsimonious genetic mechanism for signal-preference coevolution and the establishment of positive genetic covariance on which the Fisherian runaway process of sexual selection relies.

Nicotiana tabacum pollen-pistil interactions show unexpected spatial and temporal differences in pollen tube growth among genotypes.

KEY MESSAGE: This research revealed diverse PTG rates among intraspecific pollen-pistil interactions that showed variable dependency on the stigma and mature TT. Pollen-pistil interactions regulate pollen tube growth (PTG) rates and are determinants of fertilization and seed set. This research focuses on the diversity of intraspecific PTG rates and the spatial and temporal regulation of PTG among Nicotiana tabacum genotypes. Nonrandom mating within self-compatible species has been noted, but little is known on the mechanisms involved. To begin research on nonrandom mating, we took advantage of the model reproductive system of N. tabacum and used seventeen diverse N. tabacum genotypes in a complete pollination diallel to measure the diversity of intraspecific pollen-pistil interactions. The 289 intraspecific interactions showed surprisingly large differences in PTG rates. The interaction between specific males and females resulted in 18 specific combining abilities that were significantly different, indicating the importance of the specific genotype interaction in regulating intraspecific PTG. No single female or male genotype exerted overall control of PTG rates, as determined by a general combining ability analysis. Slow and fast pollen-pistil interactions showed spatial differences in growth rates along the style. Slower interactions had a slower initial PTG rate while fast interactions had faster consistent rates of growth indicating spatial regulation of PTG in the pistil. Removal of the stigma or the mature transmitting tissue (TT) showed the tissue-specific component of PTG regulation. Stigma removal resulted in slower or no change in PTG rate depending on the pollen and pistil genotypes. Removal of the TT, which necessitated removal of the stigma, showed no change, slower or unexpectedly, increased growth rates relative to growth rates without a stigma. These data show the diverse nature of pollen-pistil interactions in N. tabacum genotypes providing a system to further investigate the regulation of PTG.

What Makes Her a Material Girl?: The Influence of Childhood Economic Background and Sex Ratio on Female Preference for Male Resource Availability.

Drawing on life history theory, this research explores the moderating role of childhood economic background in the relationship between sex ratio and the female's mate preference for male resource availability. Using different priming materials, three experiments consistently found that women with a rich childhood economic background showed a stable level of mate preference for good resource-this applied regardless of male- or female-biased sex ratio. But females with a poor childhood economic background showed a higher level of preference for male resource availability under the condition of female-biased sex ratio (vs. the condition of male-biased sex ratio). These findings support the moderating role of female childhood economic background in the relationship between sex ratio and their mating preference of good resources.

Female Songbirds: The unsung drivers of courtship behavior and its neural substrates.

Songbirds hold a prominent role in the fields of neurobiology, evolution, and social behavior. Many of these fields have assumed that females lacked the ability to produce song and have therefore treated song as a male-specific behavior. Consequently, much of our understanding regarding the evolution and neural control of song behavior has been driven by these assumptions. Here we review literature from diverse fields to provide a broader perspective of the role of females in vocal communication and courtship. Recent evidence indicates that song evolved in both males and females and instances of female song are still common. The specialized neural circuit known as the "song system," which is necessary for singing in males, is also present in females, including those that do not sing, implying broader functions that include evaluating male song and controlling courtship behavior. In addition to having flexible, individualized preferences, females actively shape their social network through their interactions with males, females, and juveniles. We suggest that by developing more accurate hypotheses concerning the role of females we may better understand the evolution and neural mechanisms of song production and courtship behavior.

No male mate choice for female boldness in a bi-parental West African cichlid, the rainbow krib (Pelvicachromis pulcher).

BACKGROUND: In many species, males have a lower reproductive investment than females and are therefore assumed to increase their fitness with a high number of matings rather than by being choosy. However, in bi-parental species, also males heavily invest into reproduction. Here, reproductive success largely depends on costly parental care; with style and amount of parental effort in several cases being associated with personality differences (i.e., consistent between-individual differences in behaviour). Nonetheless, very little is known about the effect of personality differences on (male) mate choice in bi-parental species. METHODS: In the present study, we tested male mate choice for the level and consistency of female boldness in the rainbow krib, Pelviachromis pulcher, a bi-parental and territorial West African cichlid. Individual boldness was assumed to indicate parental quality because it affects parental defence behaviour. For all males and females, boldness was assessed twice as the activity under simulated predation risk. Mate choice trials were conducted in two steps. First, we let a male observe two females expressing their boldness. Then, the male could choose between these two females in a standard mate choice test. RESULTS: We tested for a male preference for behavioural (dis-)similarity vs. a directional preference for boldness but our data support the absence of effects of male and/or female boldness (level and consistency) on male mating preference. DISCUSSION: Our results suggest female personality differences in boldness may not be selected for via male mate choice.

Evaluation and hedonic value in mate choice.

Mating preferences can show extreme variation within and among individuals even when sensory inputs are conserved. This variation is a result of changes associated with evaluative mechanisms that assign positive, neutral, or negative hedonic value to stimuli-that is, label them as attractive, uninteresting, or unattractive. There is widespread behavioral evidence for differences in genes, environmental cues, or social experience leading to marked changes in the hedonic value of stimuli. Evaluation is accomplished through an array of mechanisms that are readily modifiable through genetic changes or environmental inputs, and that may often result in the rapid acquisition or loss of behavioral preferences. Reversals in preference arising from "flips" in hedonic value may be quite common. Incorporating such discontinuous changes into models of preference evolution may illuminate our understanding of processes like trait diversification, sexual conflict, and sympatric speciation.

A Stochastic Model for Reproductive Isolation Under Asymmetrical Mating Preferences.

More and more evidence shows that mating preference is a mechanism that may lead to a reproductive isolation event. In this paper, a haploid population living on two patches linked by migration is considered. Individuals are ecologically and demographically neutral on the space and differ only on a trait, a or A, affecting both mating success and migration rate. The special feature of this paper is to assume that the strengths of the mating preference and the migration depend on the trait carried. Indeed, patterns of mating preferences are generally asymmetrical between the subspecies of a population. I prove that mating preference interacting with frequency-dependent migration behavior can lead to a reproductive isolation. Then, I describe the time before reproductive isolation occurs. To reach this result, I use an original method to study the limiting dynamical system, analyzing first the system without migration and adding migration with a perturbation method. Finally, I study how the time before reproductive isolation is influenced by the parameters of migration and of mating preferences, highlighting that large migration rates tend to favor types with weak mating preferences.

A stochastic model for speciation by mating preferences.

Mechanisms leading to speciation are a major focus in evolutionary biology. In this paper, we present and study a stochastic model of population where individuals, with type a or A, are equivalent from ecological, demographical and spatial points of view, and differ only by their mating preference: two individuals with the same genotype have a higher probability to mate and produce a viable offspring. The population is subdivided in several patches and individuals may migrate between them. We show that mating preferences by themselves, even if they are very small, are enough to entail reproductive isolation between patches, and we provide the time needed for this isolation to occur as a function of the carrying capacity. Our results rely on a fine study of the stochastic process and of its deterministic limit in large population, which is given by a system of coupled nonlinear differential equations. Besides, we propose several generalisations of our model, and prove that our findings are robust for those generalisations.

Evolution of a mating preference for a dual-utility trait used in intrasexual competition in genetically monogamous populations.

The selection pressures by which mating preferences for ornamental traits can evolve in genetically monogamous mating systems remain understudied. Empirical evidence from several taxa supports the prevalence of dual-utility traits, defined as traits used both as armaments in intersexual selection and ornaments in intrasexual selection, as well as the importance of intrasexual resource competition for the evolution of female ornamentation. Here, we study whether mating preferences for traits used in intrasexual resource competition can evolve under genetic monogamy. We find that a mating preference for a competitive trait can evolve and affect the evolution of the trait. The preference is more likely to persist when the fecundity benefit for mates of successful competitors is large and the aversion to unornamented potential mates is strong. The preference can persist for long periods or potentially permanently even when it incurs slight costs. Our results suggest that, when females use ornaments as signals in intrasexual resource competition, males can evolve mating preferences for those ornaments, illuminating both the evolution of female ornamentation and the evolution of male preferences for female ornaments in monogamous species.