斜纹夜蛾的性选择行为

【目的】为了解斜纹夜蛾Spodoptera litura Fabricius体重、日龄、交配经历及形态特征对其性选择行为的影响。【方法】本实验通过标记成虫后,采用观察记录的方法对其进行探究。【结果】斜纹夜蛾雌虫的体重对雄虫的性选择影响比较明显,体重较大雄虫优先选择体重较小的雌虫(71.43%),而体重较小雄虫喜欢选择体重较大的雌虫(72.00%)。体重较大和体重较小的雄虫都能获得体重较大雌虫的交配选择,但是体重较大者被选择的机会更大(70.00%),体重较小的雄虫不能获得体重较小雌虫的选择。雄虫仅选择1日龄的雌虫,而雌虫偏向选择3日龄和5日龄雄虫。交配经历影响斜纹夜蛾的性选择,未交配的雄虫优先选择未交配的雌虫(86.67%),但未交配的雌虫则优先选择已交配的雄虫(66.67%)。雄虫的形态特征(体长、翅展、腹长、复眼间距和触角长)对雌虫性选择有较明显的影响,但雌虫的形态特征除翅展的大小外,其体长、腹长、复眼间距和触角长等形态特征在雄虫选择进行交配中的作用不大。【结论】体重、日龄、交配经历及形态特征都能不同程度影响斜纹夜蛾的性选择行为。     

Female mate choice and mating costs in the polyandrous butterflyPieris napi (Lepidoptera: Pieridae)

Males of the green-veined white butterfly (Pieris napi L.) transfer large ejaculates that represent on average 15% of their body mass when mating for a first time. Shortly after mating a male is able to transfer only a small ejaculate when mating a second time. Male ejaculate production plays a crucial role in the mating system ofP. napi because females use male-derived nutrients for egg production and somatic maintenance. Here we study how timing of female rematings and copulation duration are influenced by the mating history of their mates and, also, study if females exert mate choice to minimize their mating costs. Mating with a recently mated male increased female mating costs by increasing time in copula and mating frequency. Virgin females that mated with virgin males remated after an average of 6 days, whereas virgin females that mated with recently mated males remated after an average of 2 days. Moreover, copulations involving recently mated males lasted on average almost 7 h, whereas copulations involving virgin males lasted on average 2 h. Recently mated males were eager to remate, in spite of the fact that the size of the ejaculate they transfer is small and that they remain in copula for a long time. Hence it seems that males are more successful in the sexual conflict over mating decisions and that females do not minimize mating costs by choosing to mate preferentially with virgin males.     

Polyandry enhances offspring viability with survival costs to mothers only when mating exclusively with virgin males in Drosophila melanogaster

A prominent hypothesis for polyandry says that male–male competitive drivers induce males to coerce already‐mated females to copulate, suggesting that females are more likely to be harassed in the presence of multiple males. This early sociobiological idea of male competitive drive seemed to explain why sperm‐storing females mate multiply. Here, we describe an experiment eliminating all opportunities for male–male behavioral competition, while varying females’ opportunities to mate or not with the same male many times, or with many other males only one time each. We limited each female subject's exposure to no more than one male per day over her entire lifespan starting at the age at which copulations usually commence. We tested a priori predictions about relative lifespan and daily components of RS of female Drosophila melanogaster in experimental social situations producing lifelong virgins, once‐mated females, lifelong monogamous, and lifelong polyandrous females, using a matched‐treatments design. Results included that (1) a single copulation enhanced female survival compared to survival of lifelong virgins, (2) multiple copulations enhanced the number of offspring for both monogamous and polyandrous females, (3) compared to females in lifelong monogamy, polyandrous females paired daily with a novel, age‐matched experienced male produced offspring of enhanced viability, and (4) female survival was unchallenged when monogamous and polyandrous females could re‐mate with age‐ and experienced‐matched males. (5) Polyandrous females daily paired with novel virgin males had significantly reduced lifespans compared to polyandrous females with novel, age‐matched, and experienced males. (6) Polyandrous mating enhanced offspring viability and thereby weakened support for the random mating hypothesis for female multiple mating. Analyzes of nonequivalence of variances revealed opportunities for within‐sex selection among females. Results support the idea that females able to avoid constraints on their behavior from simultaneous exposure to multiple males can affect both RS and survival of females and offspring.     

Males mate with females even after sperm depletion in the two-spotted spider mite

Generally, males increase their reproductive success by mating with as many females as possible, whereas females increase their reproductive success by choosing males who provide more direct and indirect benefits. The difference in reproductive strategy between the sexes creates intense competition among males for access to females, therefore males spend much energy and time for competition with rival males for their reproduction. However, if they do not need to engage themselves into male competition and females are in no short supply, how many females can a male mate with and fertilize? We address this question in the two-spotted spider mite, Tetranychus urticae Koch. In this study, we investigated how many females a young, virgin male mated in 3 h, and checked whether the mated females were fertilized. We found that on average males mated with 12–13 females (range: 5–25). As latency to next mating did not change with the number of matings, the males are predicted to engage in even more matings if the mating trial were continued beyond 3 h. Copulation durations decreased with the number of matings and typically after 11 copulations with females any further copulations did not lead to fertilization, suggesting that males continued to mate with females even after sperm depletion. We discuss why spider mite males continue to display mating and copulation behaviour even after their sperm is depleted.

     

The function of Barbary macaque copulation calls.

In a wide variety of animal species, females produce vocalizations specific to mating contexts. It has been proposed that these copulation calls function to incite males to compete for access to the calling female. Two separate advantages of inciting male-male competition in this way have been put forward. The first suggests that as a result of calling, females are only mated by the highest ranking male in the vicinity (indirect mate choice hypothesis). The second proposes that copulation calling results in a female being mated by many males, thus promoting competition at the level of sperm (sperm competition hypothesis). In this paper, I give results from the first experimental study to test these hypotheses. Playback was used to examine the function of copulation calls of female Barbary macaques (Macaca sylvanus) in Gibraltar. Although rank did not affect lone males'' likelihood of approaching copulation calls, when playbacks were given to pairs of males only the higher ranking individual approached. Moreover, females were mated significantly sooner after playback of their copulation call than after playback of a control stimulus. These results suggest that the copulation calls of female Barbary macaques play a key role in affecting patterns of male reproductive behaviour, not only providing an indirect mechanism of female choice, but also promoting sperm competition by reducing the interval between copulations. Potential fitness benefits of inciting male-male competition at these two levels are discussed.     

Factors affecting female sexual receptivity in the planthopper, Prokelisia dolus

Abstract. The mating system of Prokelisia dolus Wilson (Homoptera: Delphacidae) was characterized by determining: if males and females multiply mate; when transitions occur in female sexual receptivity, what triggers sexual refractoriness; and what behaviours characterize unreceptive virgins, receptive virgins, and unreceptive mated females. Males copulated with up to six females in less than 1 h, but completely inseminate, on average, only the first four females. Females rarely mated more than once, unless males were depleted of sperm due to previous copulations or if copulation was interrupted (if duration was<2 min). Male and female calling was associated (100% and 91%, respectively) with sexual receptivity and resultant matings. The transition from unreceptive virgin to receptive (calling) mature virgin occurred 48 h posteclosion, and all were mated by day 4. Females that were sexually immature and those completely inseminated did not call. Rejection of males by females included walking away from approaching males (65%), female kicking (7%), and abdominal lifting (5%). Rejection of males was observed by immature, mature and calling, and mated females. Sexual refractoriness was not triggered by acoustic and visual stimuli or mechanical stimulation of genitalia. Refractoriness was also not triggered by reception of small quantities of sperm because some females laid a few viable eggs yet calling was not terminated. Sexual refractoriness was activated by a substance in the ejaculate as demonstrated by injection into the haemocoel of male accessory glands or testes and homogenates of seminal vesicles. This is the first study that documents the role of male ejaculate in inhibiting female sexual receptivity in Hemiptera (Homoptera).     

Age and experience affect female choice in the guppy (Poecilia reticulata)

Female choices of males, and how these choices are influenced by ecological and social factors, have been studied extensively. However, little is known about the effects of age and breeding experience on female mating decisions. We used video techniques to examine female mate choice in guppies based on the area of carotenoid (orange) pigmentation on the body. Females were presented with paired images of males, one ornamented and the other plain. Visual preference for each male was measured. Age-related changes in the criteria of choice were examined by comparing the responses of the same mature but sexually inexperienced 6-mo-old and 12-mo-old females. Effects of breeding experience on female choice were examined by comparing mate preferences of 12-mo-old female virgins with their preferences after they had mated and produced a brood. Female preferences for ornamented males with large areas of carotenoid pigment changed with age but not with mating experience. Six-month-old virgin females preferred ornamented males, whereas 12-mo-old virgin and postpartum females did not differentiate between males based on orange coloration. The results are discussed in light of life-history theory and have important implications for studies of sexual selection as well as for the design of mate-choice studies.     

Mating Status Effects on Sexual Response of Males and Females in the Parasitoid Wasp <Emphasis Type="Italic">Urolepis rufipes</Emphasis>

Although mate preferences are most commonly examined in females, they are often found in both sexes. In the parasitoid wasp Urolepis rufipes, both female and male mating status affected certain aspects of sexual interactions. Female mating status mattered only in the later stages of mating. Males did not discriminate between virgin and mated females in terms of which they contacted or mounted first. However, once mounted, most virgin females were receptive to copulation, whereas very few mated females were. Whether a male’s mating status affected his own sexual response depended on the female’s ability to respond and the stage of mating. Examining male behavior toward dead females allowed elimination of the role of female behavior in how males responded. Virgin and mated males are both attracted to dead females as evidenced by their fanning their wings at such females. However, mated males were quicker than virgin males to contact and to mount in an experiment with dead females, whereas there was no such differential response in an experiment with live females. This difference is consistent with greater female sexual responsiveness to virgin males. Male mating status also affected female receptivity to copulate. Once mounted, live virgin females were less likely to become receptive to copulation by mated males than to virgin males, but only in a choice experiment, not in a no-choice experiment.     

Male sexual cannibalism in a sand‐dwelling wolf spider with sex role reversal

Sexual cannibalism usually involves females attacking and consuming males before, during or after copulation. Sex role reversed systems may provide insight into the debate about whether it arises as mistaken identity, a spillover in female aggressiveness, foraging decisions, and/or extreme mate choice. In such systems, males may be selective and voracious to compensate for their higher reproductive costs, and thus males may be the sexually cannibalistic sex. Allocosa brasiliensis shows a reversal in sex roles and male‐biased sexual size dimorphism (the opposite of the common pattern in spiders). The present study aimed to test whether males cannibalize or mate according to female reproductive status or body characteristics. Each of 20 adult males was consecutively exposed to one virgin and one mated female, alternating the order of exposure. Males preferred to mate with virgin females in good body condition and heavier‐mated females. Males attacked 15% of virgins and 40% of mated females and cannibalized 10% and 25% of the total trials, respectively. The astonishing male cannibalistic behaviour best agrees with extreme mate choice hypotheses because attacks were more frequent on mated females of low body condition. This is the first report of male sexual cannibalism in a sex role reversed system. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 103 , 68–75.     

Sperm competition and small size advantage for males of the golden orb‐web spider Nephila edulis

Sexual selection, through female choice and/or male–male competition, has influenced the nature and direction of sexual size dimorphism in numerous species. However, few studies have examined the influence of sperm competition on size dimorphism. The orb‐web spider Nephila edulis has a polygamous mating system and extreme size dimorphism. Additionally, the frequency distribution of male body size is extremely skewed with most males being small and few large. The duration of copulation, male size and sexual cannibalism have been identified as the significant factors determining patterns of sperm precedence in spiders. In double mating trials, females were assigned to three treatments: either they mated once with both males or the first or the second male was allowed to mate twice. Paternity was strongly associated with the duration of copulation, independent of mating order. Males that were allowed to mate twice not only doubled the duration of copulation but also their paternity. Small males had a clear mating advantage, they copulated longer than large males and fertilized more eggs. Males of different sizes used different tactics to mate. Large males were more likely to mate through a hole they cut into the web, whereas small males approached the female directly. Furthermore, small males usually mated at their first attempt but large males required several attempts before mating took place. There was no obvious female reaction towards males of different sizes.     

Sexual selection when fertilization is not guaranteed

Abstract Much of the theory of sexual selection assumes that females do not generally experience difficulties getting their eggs fertilized, yet sperm limitation is occasionally documented. How often does male limitation form a selection for female traits that improve their mating rate? The question is difficult to test, because if such traits evolve to be efficient, sperm limitation will no longer appear to be a problem to females. Here, we suggest that changes in choosiness between populations, and in particular between virgin and mated females, offer an efficient way to test this hypothesis. We model the “wallflower effect,” that is, changes in female preferences due to time and mortality costs of remaining unmated (for at least some time). We show that these costs cause adaptive reductions of female choice, even if mate encounter rates appear high and females only rarely end their lives unfertilized. We also consider the population consequences of plastic or fixed mate preferences at different mate encounter rates. If mate choice is plastic, we confirm earlier verbal models that virgins should mate relatively indiscriminately, but plastic increase of choosiness in later matings can compensate and intensify sexual selection on the male trait, particularly if there is last male sperm precedence. Plastic populations will cope well with unusual conditions: eagerness of virgins leads to high reproductive output and a relaxation of sexual selection at low population densities. If females lack such plasticity, however, population‐wide reproductive output may be severely reduced, whereas sexual selection on male traits remains strong.     

Influence of Female Copulation Calls on Male Sexual Behavior in Captive Macaca fascicularis

We investigated the function of copulation calls—vocalizations by females during mating—in captive groups of long-tailed macaques. We tested predictions of the contest-competition, sperm competition, synchronized orgasms, mate again, alpha-male notification and graded-signal hypotheses. We observed 371 copulations of 36 females wherein the presence or absence of a copulation call was clear. Females call equally often with different males and shortly after ejaculation. Copulation calls occurred equally with copulations with and without ejaculation. Calls did not incite disruptions of the mating. Following calls females mated again, more often than expected, with their mating partner. Both pregnant and fertile females uttered copulation calls. Two females conceived and mated mainly with the alpha male then. We conclude that copulation calls do not incite male contest competition for sexual access to females and that it is unlikely that calls synchronize male and female orgasms. Several hypotheses remain plausible, but not all predictions are borne out unequivocably. This alerts us to the possibility that the calls could have multiple beneficial effects; natural selection might strike a compromise among functions. Investigation of the mate again, sperm competition and alpha-male notification hypotheses, and of hypotheses not tested in our study concerning female breeding overlap and female-female agonism, is required.     

Sperm storage mediated by cryptic female choice for nuptial gifts

Polyandrous females are expected to discriminate among males through postcopulatory cryptic mate choice. Yet, there is surprisingly little unequivocal evidence for female-mediated cryptic sperm choice. In species in which nuptial gifts facilitate mating, females may gain indirect benefits through preferential storage of sperm from gift-giving males if the gift signals male quality. We tested this hypothesis in the spider Pisaura mirabilis by quantifying the number of sperm stored in response to copulation with males with or without a nuptial gift, while experimentally controlling copulation duration. We further assessed the effect of gift presence and copulation duration on egg-hatching success in matings with uninterrupted copulations with gift-giving males. We show that females mated to gift-giving males stored more sperm and experienced 17% higher egg-hatching success, compared with those mated to no-gift males, despite matched copulation durations. Uninterrupted copulations resulted in both increased sperm storage and egg-hatching success. Our study confirms the prediction that the nuptial gift as a male signal is under positive sexual selection by females through cryptic sperm storage. In addition, the gift facilitates longer copulations and increased sperm transfer providing two different types of advantage to gift-giving in males.     

Silk‐ and volatile‐based male mate choice in the genital plug‐producing spider

Female mating history can have a strong effect on male fertilization success. Although males often prefer to mate with virgin females, they often also engage with mated females. As the intensity of sperm competition can differ among mated females, males are expected to evolve means to identify their status. In spiders, males often use female silk to gather information about female quality. Males of many spider species deposit mating plugs into female genitalia to hinder further copulations. We tested whether males of the foliage‐dwelling, plug‐producing spider Philodromus cespitum, which is an important natural enemy of pests, discriminate between females of different mating status and whether they can determine the extent of genital plugging in mated females solely on the basis of cues gained from deposited female silk. We presented males with draglines of females that varied in either mating status (virgin vs. mated), the extent of plugging (small vs. big plug), or the age of the plug (fresh vs. old plug) and examined their mate preferences. Additionally, we tested whether males were attracted to volatile cues produced by female bodies. Our experiments revealed that males preferred draglines of virgin females to those of mated females, and mated females with small plugs to those with large plugs. They were also attracted to female volatile cues. This study suggests that males are able to extract fine‐scale information on mating status from female draglines.     

Reproductive strategies of the larval parasitoid Microplitis croceipes

Mate choice may have important consequences for offspring sex ratio and fitness of haplodiploid insects. Mate preference of females of the solitary larval parasitoid Microplitis croceipes (Cresson) (Hymenoptera: Braconidae) for virgin and mated males, and vice versa, and the reproductive consequences (i.e., the sex ratio expressed as the proportion of male offspring) were examined in choice and non‐choice experiments. In addition, the effect of repeated rapid and daily copulation of an individual male on the sex ratio of offspring of the female mates was assessed. Males preferred virgins over mated females, whereas females copulated with a male irrespective of his mating status. In both the rapid and daily copulation assay, females copulating with a male that had copulated five times or more produced a higher sex ratio than females that had copulated with a virgin male. Females that copulated with virgin males once or twice produced a significantly and considerably lower sex ratio than females that first copulated with a sperm‐depleted male followed by a virgin male. This indicates that copulating with a sperm‐depleted male has costs and limits acquisition by the female of sperm from virgin males.     

Male-male competition and large size mating advantage in European earwigs, Forficula auricularia

European earwigs are sexually dimorphic in forceps shape and length. Male forceps are thought to be weapons in male contests for access to females, but recent findings suggest that females choose males on the basis of their forceps length. I investigated sexual selection on forceps length and body size and the occurrence of male-male competition. When I controlled for forceps length experimentally and statistically, relatively heavy males had greater copulation success than relatively light males. When I controlled for body size, males with relatively longer forceps had no tendency for greater copulation success than males with shorter forceps. Relatively heavy males more often took over copulations from smaller males than vice versa. Male contests were important for the outcome of mate competition, as males commonly interrupted and took over copulations. My results therefore suggest that intrasexual selection is significant in competition for copulations in male earwigs, and acts on body size. This contrasts with previous findings, which have shown intersexual selection on forceps length to be important. However, both modes of sexual selection may be acting through a two-stage process, where male-male competition first determines which males have access to females, and then through female choice among available males. Morphological measurements supported the conclusion that forceps length and body size are male secondary sexual characters, as these characters had large variance and skewed distributions in males, but were normally distributed in females. Copyright 2000 The Association for the Study of Animal Behaviour.     

Female Copulation Calls in Guinea Baboons: Evidence for Postcopulatory Female Choice?

We tested the hypothesis that primate female copulation calls are a form of postcopulatory female choice. We collected data on female sexual swellings, sexual and agonistic behavior, copulation calls and postcopulatory behavioral interactions in a multimale-multifemale captive group of Guinea baboons over a 3-mo period. Males copulated with only a few females, and females copulated with only 1 or 2 different males in the group, suggesting a harem-like mating system similar to that of hamadryas and gelada baboons. Female copulations were most likely to occur at peak sexual swellings and male copulatory success was accounted for by dominance rank and age. Variation in female tendencies to call after copulation is best explained by the copulatory success of the male with which each female copulated the most and by the number of copulating partners. The findings are consistent with predictions that calls are likely to be associated with copulation with preferred males and the risk of sperm competition. The prediction that copulation calls increased the probability of postcopulatory mate guarding is also supported. Taken together, the findings suggest that female copulation calls may play an important role in postcopulatory sexual selection and in particular in the expression of postcopulatory female choice in primate species in which females have little opportunity to choose their mates or female mate choice is costly or both.     

Copulation patterns in the golden orb-web spider Nephila madagascariensis

A consequence of multiple mating by females can be that the sperm of two or more males directly compete for the fertilisation of ova inside the female reproductive tract. Selection through sperm-competition favours males that protect their sperm against that of rivals and strategically allocate their sperm, e.g., according to the mating status of the female and the morphology of the spermatheca. In the majority of spiders, we encounter the otherwise unusual situation that females possess two independent insemination ducts, both ending in their own sperm storage organ, the spermatheca. Males have paired mating organs, but generally can only fill one spermatheca at a time. We investigated whether males of the African golden orb-web spider Nephila madagascariensis can prevent rival males from mating into the same spermatheca and whether the mating status of the female and/or the spermatheca causes differences in male mating behaviour. There was no significant difference in the duration of copulations into unused spermathecae of virgin and mated females. We found that copulations into previously inseminated spermathecae were generally possible, but shorter than copulations into the unused side of mated females or with virgins. Thus, male N. madagascariensis may have an advantage when they mate with virgins, but cannot prevent future males from mating. However, in rare instances, parts of the male genitals can completely obstruct a female genital opening.     

Male Performance and Body Size Affect Female Re-Mating Occurrence in the Orb-Web Spider Leucauge mariana (Araneae, Tetragnathidae)

Females can affect male probabilities of paternity success through behavioural, morphological and/or physiological processes occurring during or after copulation. These processes under female-control include the acceptance or rejection of mating attempts by subsequent males. Leucauge mariana is an orb weaving spider that shows male mate guarding of penultimate females, male–male competition on female webs and copulatory plugs, suggesting a polyandric mating system. The aim of the present study was to ascertain whether male behaviour during courtship and copulation in L. mariana relate with female re-mating decisions. Forty-three virgin females were exposed to up to three males until they mated. In 24 cases, the copulatory plug was absent after mating and females were exposed the next day to up to three other males. Eighteen females accepted a second mating. Relatively larger females were more receptive to second matings and were more likely to copulate if the second male was smaller. Longer duration of female tapping and abdominal bobbing during courtship, and first copulations with less short insertions and more flubs, were associated with increased female acceptance to second matings. The results indicate cryptic female choice on male courtship and copulatory performance and suggest female-control over the determination of male mating success in this spider species.     

Age,Experience and Sex – Do Female Bulb Mites Prefer Young Mating Partners?

In species where advancing sire age is associated with decreased progeny fitness, female resistance to mating with old partners can be expected to evolve. In polyandrous species, such resistance may be contingent on female mating experience: virgins should be relatively indiscriminate to ensure egg fertility, whereas non‐virgins can be expected to base their re‐mating decisions on the age of their previous versus potential new partners, and ‘trade‐up’ if previously mated with old males. Here, we tested these predictions using a promiscuous and relatively long‐living bulb mite (Rhizoglyphus robini), in which old sire age is associated with decreased fecundity of daughters. In a fully factorial design, we applied two male treatments, young and old, and three female treatments, virgin, previously mated to an old male and previously mated to a young male. Consistent with earlier studies, we observed a reduced mating success of old males. However, we found no support for attributing this result to female discrimination, as female behavior in response to male mounting attempts was not affected by the age of the suitor, or by its interaction with the age of the female’s previous mate. Interestingly, females were passive during 93% of male mounting attempts observed, suggesting that once they are located by a male, they exert little control over copulation. Old males had lower mate‐searching activity and were less efficient in obtaining matings (lower success rate per mounting attempt), suggesting a decreased mate‐securing ability because of aging. Overall, our results suggest that in bulb mites, male ability to secure mates declines with age, whereas they do not support the prediction that females actively discriminate against old partners.