红眼突变灰飞虱的生物学特性和交配优势

灰飞虱Laodelphax striatellus是我国重要水稻害虫之一, 表型变异可能影响灰飞虱的配偶选择性和种群特性。本实验采用生命表构建法研究了红眼突变灰飞虱的繁殖力、 内禀增长率等种群生命参数, 然后以1红眼雌虫、 1红眼雄虫和1纯合黑眼雄虫（♀rr×♂rr♂BB）或1红眼雄虫、 1红眼雌虫和1纯合黑眼雌虫（♀rr♀BB×♂rr）配对模式以及不同比例红眼成虫群体配对模式研究红眼突变对灰飞虱交配竞争力的影响。结果表明红眼突变灰飞虱除若虫死亡率（17.1%）显著高于正常个体（10.3%） (P<0.05)外, 其他生物学指标如繁殖力、 卵孵化历期、 若虫发育历期、 成虫寿命、 内禀增长率等与正常个体无显著差异。但红眼突变对灰飞虱配偶选择性有一定的影响。♀rr×♂rr♂BB和♀rr♀BB×♂rr组合F1代红眼和黑眼分离比例卡方试验值为18.15和14.99, 大于理论值。当红眼与黑眼个体以2︰8比例配对时, 红眼灰飞虱雄虫存在交配优势, 其后代红眼个体数大于期望值。这些结果为进一步研究灰飞虱红眼突变机理和利用红眼基因标记研究灰飞虱遗传分化奠定了基础     

Male sperm donation consequences in single and double matings in Anisopteromalus calandrae

Abstract. The number of spermatozoa that a male transfers to the female during copulation is a main component of its individual fitness, especially under the pressure of sperm competition. This paper presents experimental results on the direct relationship between the male's sperm investment and its paternity in the offspring of dual-mated females. An eye colour mutant (red-eyed) is used to study the differences in the mating and fertilization abilities of males through observation of single and dual matings of females in Anisopteromalus calandrae (Hymenoptera, Chalcidoidea, Pteromalidae). Experimentally, females accept dual matings only in the simultaneous presence of two males. Counts of spermatozoa in the seminal vesicles of virgin males show that red-eyed males have more sperm than wild-eyed ones (approximately 1.46-fold greater). Red- and wild-eyed males do not differ in their mating behaviour and females mate indifferently with both phenotypes. Compared with once-mated females, double-mated females increase neither sperm storage nor lifetime fecundity, and the offspring sex ratio is female-biased. Females mated with two males of different phenotypes produce offspring of both phenotypes throughout their reproductive life, whatever the order of males in the copulation sequence. Any mating pattern appears to produce more red- than wild-eyed offspring (between 1.45- and 1.88-fold greater). Thus, proportions of offspring of each male match the proportions of their sperm potential. With no preference of female for red-eye or wild-eye males being demonstrated at either behavioural or physiological levels, a male's investment in sperm quantity appears to determine its individual reproductive success, at least in these experimental conditions.     

Ontogenetic colour change signals sexual maturity in a non-territorial damselfly

Conspicuous colouration increases male reproductive success through female preferences and/or male–male competition. Despite the advantages of conspicuous colouration, inconspicuous male morphs can exist simultaneously in a population due to genetic diversity, condition dependence or developmental constraints. We are interested in explaining the male dichromatism in Xanthagrion erythroneurum damselflies. We reared these damselflies in outdoor insectaries under natural conditions and showed that this species undergoes ontogenetic colour changes. The younger males are yellow and change colour to red 6–7 days after their emergence. We took red and yellow male reflectance spectra and found that red males are brighter than yellow males. Next, we aimed to determine whether ontogenetic colour change signals sexual maturity with field observations and laboratory experiments. Our field observational data showed that red males are in higher abundance in the breeding territory, and they have a higher mating frequency than yellow males. We confirmed these field observations by enclosing a red and a yellow male with two females and found that yellow males do not mate in presence of red males. To determine whether colour change signals sexual maturity, we measured mating success of males before and after colour changes by enclosing a single male at different age (day 3-day 7) and colour (yellow, intermediate and red) with a single female in a mating cage. Males did not mate when yellow but the same male mated after it changed colour to red, suggesting the ontogenetic colour change signals sexual maturity in this species. Our study shows that male dichromatism can be age-dependent and ontogenetic colour change can signal age and sexual readiness in non-territorial insects.     

Female multiple mating in wild and laboratory populations of the two-spot ladybird, Adalia bipunctata

Female mating rate is an important variable for understanding the role of females in the evolution of mating systems. Polyandry influences patterns of sexual selection and has implications for sexual conflict over mating, as well as for wider issues such as patterns of gene flow and levels of genetic diversity. Despite this, remarkably few studies of insects have provided detailed estimates of polyandry in the wild. Here we combine behavioural and molecular genetic data to assess female mating frequency in wild populations of the two-spot ladybird, Adalia bipunctata (Coleoptera: Coccinellidae). We also explore patterns of sperm use in a controlled laboratory environment to examine how sperm from multiple males is used over time by females, to link mating with fertilization. We confirm that females are highly polyandrous in the wild, both in terms of population mating rates (approximately 20% of the population found in copula at any given time) and the number of males siring offspring in a single clutch (three to four males, on average). These patterns are consistent across two study populations. Patterns of sperm use in the laboratory show that the number of mates does not exceed the number of fathers, suggesting that females have little postcopulatory influence on paternity. Instead, longer copulations result in higher paternity for males, probably due to the transfer of larger numbers of sperm in multiple spermatophores. Our results emphasize the importance of combining field and laboratory data to explore mating rates in the wild.     

An orange-eye mutant of the brown planthopper,Nilaparvata lugens (Hemiptera: Delphacidae)

An orange-eye mutant of the brown planthopper (BPH), Nilaparvata lugens (Stål), was found in a green house and has since been maintained together with a normal-eye phenotype of BPH in an insectary. The orange color was expressed in all developmental stages of BPH: the eye spots of eggs and the eyes of nymphs and adults of both sexes and wing forms. Cross-mating results suggested that the inheritance of the orange-eye phenotype is controlled by a single autosomal recessive allele. The gene symbol related to this mutant was designated as “org”. Developmental duration and mortality of nymphal stages were not significantly different between the normal phenotype (homozygous and heterozygous) and the mutant. In addition, reproduction was not significantly different among mating combinations of the three BPH genotypes (+/+, +/org, org/org). The effect of eye color on mating of BPH was insignificant in a mate choice test which consisted of one orange-eye female, one orange-eye male, and one homozygous normal-eye male. Offspring produced by the orange-eye female BPH hatched and developed into adults normally, indicating that the eye color mutant found in this study is different from the red-eye BPH (Mochida, 1970) which showed the egg lethal effect in the red-eye BPH female.     

Female mating status does not affect male mating behavior in the West Indian sweetpotato weevil, Euscepes postfasciatus

Because multiple mating by females encourages sperm competition, the assessment of female mating status before insemination is important for males in order to avoid the risk of sperm competition or to intensify sperm competition. When interacting with females before sperm transfer, males can alter their mating tactics according to the risk or intensity of sperm competition. Information on how mating systems are associated with sperm competition is essential for sterile insect technique eradication programs, which depend on successful mating of released sterile males with wild females. We tested whether males of the West Indian sweetpotato weevil, Euscepes postfasciatus (Fairmaire) (Coleoptera: Curculionidae), adjusted their mating behavior in response to female mating experience and/or age. As virgin/young female weevils accepted males more easily than non-virgin/old females, assessing females before insemination can be adaptive for male weevils. We found that E. postfasciatus males were unable to adjust their mating tactics in response to female mating status. Although this mating strategy would be costly for individual male weevils, the ability in males to discriminate female mating status can prevent the chance of mating with already-mated females containing the sperm of wild male(s). Therefore, the mating tactics of male E. postfasciatus are advantageous for sterile insect technique eradication programs.     

Effects of multiple mating and male eye span on female reproductive output in the stalk-eyed fly, Cyrtodiopsis dalmanni

Females of the stalk-eyed fly, Cyrtodiopsis dalmanni, mate repeatedly during their lifetime and exhibit mating preferencefor males with large eye span. How these mating decisions affectfemale fitness is not fully understood. In this study, we examinedthe effects of multiple mating and male eye span on short-termreproductive output in this species. Experiments that manipulatedthe number of copulations and partners a female received suggested that obtaining a sufficient sperm supply is an important benefitassociated with multiple mating. The average percentage offertile eggs laid by females increased as a function of matingfrequency and ranged from 40% for females mated once, to 80%for females mated continuously. In addition, a high proportionof copulations in this species appeared to be unsuccessful. One-third of all females mated once laid less than 10% fertileeggs. There was no significant difference in reproductive performancebetween females mated to multiple partners and females matedto a single partner. There was also no indication that femalesreceived any short-term reproductive benefits from mating withmales with large eye span. In fact, females mated to males with short eye span laid a higher percentage of fertile eggs thanfemales mated to large eye span males.     

Males mate indiscriminately in the tropical jumping spider Hasarius adansoni (Audouin, 1826)

Traditionally, sexual selection has been seen as a process in which choosy females select non‐choosy males. Recent studies, however, have challenged this view by showing that males can also be choosy in many species. We assessed the sexual preferences in males of the tropical jumping spider Hasarius adansoni (Audouin, 1826). We measured mating effort in males and determined how female quality influences offspring quality, quantity, and survival. We also estimated total sperm load and how much sperm was invested in a mating with a particular female. We found no evidence of male mating effort in terms of mating frequency nor sperm investment. Similarly, there was no relationship between female quality (i.e., size and condition) and offspring quality (i.e., survival and feeding performance) or quantity. We found strong evidence that the sperm invested in a particular female is a function of the amount of sperm the male had available for usage at that particular mating. The fact that males probably find females sequentially, along with the lack of relationship between female quality and offspring quality/quantity, likely explains the lack of differences in mating effort by males.     

Colour-associated mating success in a polymorphic Ladybird Beetle, Harmonia axyridis

1. Body size is often an important character in mating success, but has been only infrequently mentioned in regard to colour polymorphism. In this study, mating success was investigated in a colour polymorphic Ladybird Beetle, Harmonia axyridis , with reference both to colour morph and to body size.
2. In the non-melanic males the mating individuals were significantly larger than solitary individuals, while in melanic males there was no significant difference.
3. The mating pattern was close to random mating with respect to colour morph and there was no significant deviation.
4. The results suggest both body size and colour morph affect the male mating success and males of different body size obtain mating advantage according to the colour morph. Colour polymorphism in this species is controlled by alleles on a single locus. Thus, the alleles on that locus significantly influence the effect of selection on the quantitative character.     

Effects of age and repeated mating on male sperm supply and paternity in a parasitoid wasp

Post-copulatory paternity biases after female multiple mating are major constraints on both male and female reproductive systems. The outcome of paternity in certain situations is only controlled directly by male sperm stock. This was tested experimentally in the parasitoid wasp Anisopteromalus calandrae (Howard) (Hymenoptera: Pteromalidae), in which sperm stocks are small (several hundred) and the fertilizing efficiency of stored sperm is high (the ratio of sperm stored/fertilized eggs is about 0.75). Sperm in seminal vesicles and paternity of males of different status (virgin young, virgin old, or young previously mated) were measured after female single and double mating. The amount of sperm in the seminal vesicle differed according to male status (increasing from previously mated males to old males), but there was no difference in sperm stored by females after a single mating. In double mating experiments with two males of different status, paternity increased linearly with the relative amount of sperm in seminal vesicles. Paternity distribution conforms to 'a fair raffle' of sperm from both donors following complete mixing of sperm prior to fertilization. Thus, in a female multiple mating context, male fitness depends principally on their sperm stock, which in turn depends on life history parameters, such as age and previous mating.     

Male mating rate is constrained by seminal fluid availability in bedbugs, Cimex lectularius

Sexual selection, differences in reproductive success between individuals, continues beyond acquiring a mating partner and affects ejaculate size and composition (sperm competition). Sperm and seminal fluid have very different roles in sperm competition but both components encompass production costs for the male. Theoretical models predict that males should spend ejaculate components prudently and differently for sperm and seminal fluid but empirical evidence for independent variation of sperm number and seminal fluid volume is scarce. It is also largely unknown how sperm and seminal fluid variation affect future mating rate. In bedbugs we developed a protocol to examine the role of seminal fluids in ejaculate allocation and its effect on future male mating rate. Using age-related changes in sperm and seminal fluid volume we estimated the lowest capacity at which mating activity started. We then showed that sexually active males allocate 12% of their sperm and 19% of their seminal fluid volume per mating and predicted that males would be depleted of seminal fluid but not of sperm. We tested (and confirmed) this prediction empirically. Finally, the slightly faster replenishment of seminal fluid compared to sperm did not outweigh the faster decrease during mating. Our results suggest that male mating rate can be constrained by the availability of seminal fluids. Our protocol might be applicable to a range of other organisms. We discuss the idea that economic considerations in sexual conflict research might benefit from distinguishing between costs and benefits that are ejaculate dose-dependent and those that are frequency-dependent on the mating rate per se.     

Male body size and condition affects sperm number and production rates in mosquitofish,Gambusia holbrooki

Sperm number is an important predictor of paternity when there is sperm competition. Sperm number is often measured as maximum sperm reserves, but in species where mating is frequent, males will often be replenishing their reserves. Thus, variation in how quickly males can produce sperm is likely to be important in determining male success in sperm competition. Despite this, little is known about how male size, body condition or diet affects sperm production rates. We counted sperm number in large and small Gambusia holbrooki (eastern mosquitofish) after 3 weeks on either a high or low food diet. Sperm number was significantly higher in both larger males and in well‐fed males. We then stripped ejaculates again either 1, 2, 3, 4 or 5 days later to investigate subsequent sperm production. The rate of sperm replenishment was influenced by an interaction between size and diet. Large, well‐fed males had consistently high levels of sperm available over the 5 days (i.e. rapid replenishment), whereas small poorly fed males showed consistently low levels of sperm availability over the 5 days (i.e. slow replenishment). In contrast, large, poorly fed and small, well‐fed males increased their sperm numbers over the first 3 days (i.e. intermediate replenishment). Our study highlights that when mating is frequent and sperm competition is high, size and condition dependence of maximal sperm number and of sperm production rate might both contribute to variation in male reproductive success.     

Sperm competition and the dynamics of X chromosome drive: stability and extinction

Several empirical studies of sperm competition in populations polymorphic for a driving X chromosome have revealed that Sex-ratio males (those carrying a driving X) are at a disadvantage relative to Standard males. Because the frequency of the driving X chromosome determines the population-level sex ratio and thus alters male and female mating rates, the evolutionary consequences of sperm competition for sex chromosome meiotic drive are subtle. As the SR allele increases in frequency, the ratio of females to males also increases, causing an increase in the male mating rate and a decrease in the female mating rate. While the former change may exacerbate the disadvantage of Sex-ratio males during sperm competition, the latter change decreases the incidence of sperm competition within the population. We analyze a model of the effects of sperm competition on a driving X chromosome and show that these opposing trends in male and female mating rates can result in two coexisting locally stable equilibria, one corresponding to a balanced polymorphism of the SR and ST alleles and the second to fixation of the ST allele. Stochastic fluctuations of either the population sex ratio or the SR frequency can then drive the population away from the balanced polymorphism and into the basin of attraction for the second equilibrium, resulting in fixation of the SR allele and extinction of the population.     

Sperm depletion may not limit male reproduction in a capital breeder

Male reproduction is not only constrained by the number of encountered females but also by physiological limitations, including sperm production and the ability to sustain courtship and mating. Over a breeding season, sperm stores may drop in tandem with male energetic reserves or motivation, confounding the constraints imposed by sperm quantity with other correlated physiological limitations. We used wood frogs (Lithobates sylvaticus) to test whether explosive capital breeders are functionally limited by sperm depletion. We paired males with four conspecific females in succession and counted all of the fertilized and unfertilized eggs that each pair produced. In general, males did not experience a progressive decrease in fertilization rates with each mating (which is characteristic of sperm depletion). Instead, a few males experienced complete fertilization failure during their third and/or fourth mating, perhaps as a result of physical exhaustion, loss of motivation or hormonal changes. This pattern suggests that, even if male wood frogs do become increasingly sperm depleted over a breeding season, they are not necessarily limited by sperm. Understanding how and why fertilization rates change over multiple matings (i.e. incremental decrease vs. all‐or‐nothing) will help clarify the role of sperm depletion in limiting reproduction.     

Reversed sexual conflict in a promiscuous antelope

A general tenet of sexual conflict theory is that males have higher optimum mating rates than do females and therefore should be more persistent when it comes to mating. However, in promiscuous species, females might benefit from high mating rates as a result of increased conception probability with favored males, whereas favored males benefit from mating selectively because of sperm depletion. When this results in higher optimum mating rates for females than for males, there is potential for reversed sexual conflicts between persistent females and resistant males. Here I report evidence of such a reversed sexual conflict in a promiscuous antelope, the African topi. Rather than mating randomly, favored males prefer to balance mating investment equally between females as predicted by strategic sperm allocation theory. Females, however, enhance their probability of mating with favored males through aggression toward mating pairs. Supporting the idea that aggressive females thereby harass males to mate at a rate that is suboptimal from the males' perspective, males become increasingly likely to counterattack aggressive females with whom they have already mated disproportionately, and such male counterattacks are associated with refusal to mate with the aggressive females. This study points to reversed sexual conflict as a more significant evolutionary force in promiscuous mammals than previously thought; however, such conflicts probably often go unnoticed because males, in contrast to females, can avoid mating without conspicuous resistance.     

Condition‐dependent ejaculate production affects male mating behavior in the common bedbug Cimex lectularius

Food availability in the environment is often low and variable, constraining organisms in their resource allocation to different life‐history traits. For example, variation in food availability is likely to induce condition‐dependent investment in reproduction. Further, diet has been shown to affect ejaculate size, composition and quality. How these effects translate into male reproductive success or change male mating behavior is still largely unknown. Here, we concentrated on the effect of meal size on ejaculate production, male reproductive success and mating behavior in the common bedbug Cimex lectularius. We analyzed the production of sperm and seminal fluid within three different feeding regimes in six different populations. Males receiving large meals produced significantly more sperm and seminal fluid than males receiving small meals or no meals at all. While such condition‐dependent ejaculate production did not affect the number of offspring produced after a single mating, food‐restricted males could perform significantly fewer matings than fully fed males. Therefore, in a multiple mating context food‐restricted males paid a fitness cost and might have to adjust their mating strategy according to the ejaculate available to them. Our results indicate that meal size has no direct effect on ejaculate quality, but food availability forces a condition‐dependent mating rate on males. Environmental variation translating into variation in male reproductive traits reveals that natural selection can interact with sexual selection and shape reproductive traits. As males can modulate their ejaculate size depending on the mating situation, future studies are needed to elucidate whether environmental variation affecting the amount of ejaculate available might induce different mating strategies.     

Male crickets adjust the viability of their sperm in response to female mating status

Sperm competition theory predicts that males should allocate sperm according to the number of competing ejaculates. Prudent allocation of sperm in response to different levels of sperm competition has been found across a number of taxa; however, some studies suggest that males may not always allocate sperm as expected. Here we examine sperm allocation in the Australian field cricket Teleogryllus oceanicus, using female mating status (virgin, singly mated, or multiply mated) to manipulate male perception of sperm competition risk and intensity. Consistent with theory, we found that male crickets adjust their ejaculates in response to female mating status. However, rather than altering the absolute numbers of sperm transferred to a female, males altered the quality of their sperm. Males ejaculated sperm of low viability (proportion of live vs. dead sperm) when mating with virgins, increased sperm viability when mating with singly mated females, but reduced sperm viability when mating with multiply mated females. Our results show that variation in ejaculate quality can be an important aspect of strategic ejaculation by males and suggest caution in the interpretation of studies in which males do not appear to allocate sperm according to theory.     

Worthless and Nutritive Nuptial Gifts: Mating Duration,Sperm Stored and Potential Female Decisions in Spiders

In nuptial gift-giving species females sometimes select their potential mates based on the presence and size of the gift. But in some species, such as the Neotropical polyandrous spider Paratrechalea ornate male gifts vary in quality, from nutritive to worthless, and this male strategy can be in conflict with female nutritional benefits. In this species, males without gifts experience a reduction in mating success and duration, while males that offer worthless or genuine nutritive gifts mate with similar frequencies and durations. The female apparently controls the duration of copulation. Thus, there is scope for females to favour males offering gifts and further if these are nutritious, via post-copulatory processes. We first tested whether females differentially store sperm from males that offer the highest nutritional benefits by experimentally presenting females with males that offer either nutritive or worthless gifts (uninterrupted matings). Second, we carried out another set of experiments to examine whether females can select sperm based only on gift presence. This time we interrupted matings after the first pedipalp insertion, thus matching number of insertions and mating duration for males that: offered and did not offer gift. Our results showed that the amount of sperm stored is positive related to mating duration in all groups, except in matings with worthless gifts. Gift presence itself did not affect the sperm stored by females, while they store similar number of sperm in matings with males offering either nutritive or worthless gifts. We discuss whether females prefer males with gifts regardless, if content, because it represents an attractive and/or reliable signal. Or alternatively, they prefer nutritive nuptial gifts, as they are an important source of food supply and/or signal of male donor ability.     

Age-related sperm transfer and sperm competitive ability in the male hide beetle

The influence of male age on reproductive success after a singlemating has been explored widely; however, few studies have investigatedwhether quantitative or qualitative differences in male spermare responsible for the observed patterns. Moreover, the roleof male age on sperm competitive ability has been largely ignored.We examined the importance of male age on the probability andamount of sperm transferred during a single mating and exploredwhether sperm competitive ability varies with male age in thehide beetle Dermestes maculatus, a species where sperm viabilitydoes not vary with male age. We also investigated whether spermtransfer rates varied with female age. We found that the probabilityof sperm transfer and the amount of sperm transferred variedwith male, but not female, age. All males performed behaviorallysuccessful copulations, but intermediate-age and old males weremore likely to transfer sperm successfully and also transferreda greater quantity of sperm than young males. Old males wereless likely to transfer sperm than intermediate-age males, butif they did transfer sperm successfully, they transferred comparableamounts. Sperm competitive ability varied with male age andreflected the quantity of sperm transferred. On average, intermediate-agemales achieved greater fertilization success when competingagainst young or old males than when competing against otherintermediate-age males. Old males were poor competitors againstintermediate-age males, but they achieved significantly higherrates of fertilization when competing against young males. Ourfindings suggest that quantitative differences in the amountof sperm transferred determine male success in sperm competitionin the hide beetle.     

Strategic sperm allocation in the Small White butterfly Pieris rapae (Lepidoptera: Pieridae)

1. In species where females mate multiply, it is important for males to recuperate quickly in order to maximize their fertilization success. Butterflies produce a spermatophore at mating containing accessory secretions and sperm of two types: a large number of non-fertile 'apyrene' sperm and fewer fertile 'eupyrene' sperm. Many butterfly species eclose with most nutrients for reproduction already present. Males must therefore decide how to allocate resources to the various spermatophore components at any given mating.
2. Recovery rates of apyrene and eupyrene sperm number and spermatophore size was studied in the polyandrous Small White butterfly Pieris rapae . The mass of the first spermatophore increases with time since eclosion, as does the number of both types of sperm. Similarly, on a male's second mating, both the mass of the spermatophore and the number of sperm increases with time since the first mating.
3. However, the rate of increase in eupyrene sperm numbers is higher after the first mating. The difference in rate of increase may be the result of different probabilities of virgin and non-virgin males obtaining future matings.
4. Males have a sperm storage organ, the duplex, in which they retain sperm after their first mating. This ensures that high sperm numbers are available for their second mating, even when remating only 1 h later. Thus, males do not ejaculate all available sperm on any given mating, and seem to have different strategies on their first and second matings.
5. It can be argued that Small White butterfly males allocate sperm strategically according to the probability of obtaining subsequent matings, and the level of sperm competition.