Geographic parthenogenesis and the common tea‐tree stick insect of New Zealand

Worldwide, parthenogenetic reproduction has evolved many times in the stick insects (Phasmatidae). Many parthenogenetic stick insects show the distribution pattern known as geographic parthenogenesis, in that they occupy habitats that are at higher altitude or latitude compared with their sexual relatives. Although it is often assumed that, in the short term, parthenogenetic populations will have a reproductive advantage over sexual populations; this is not necessarily the case. We present data on the distribution and evolutionary relationships of sexual and asexual populations of the New Zealand stick insect, Clitarchus hookeri. Males are common in the northern half of the species’ range but rare or absent elsewhere, and we found that most C. hookeri from putative‐parthenogenetic populations share a common ancestor. Female stick insects from bisexual populations of Clitarchus hookeri are capable of parthenogenetic reproduction, but those insects from putative‐parthenogenetic populations produced few offspring via sexual reproduction when males were available. We found similar fertility (hatching success) in mated and virgin females. Mated females produce equal numbers of male and female offspring, with most hatching about 9–16 weeks after laying. In contrast, most eggs from unmated females took longer to hatch (21–23 weeks), and most offspring were female. It appears that all C. hookeri females are capable of parthenogenetic reproduction, and thus could benefit from the numerical advantage this yields. Nevertheless, our phylogeographic evidence shows that the majority of all‐female populations over a wide geographic area originate from a single loss of sexual reproduction.     

The fitness effects of delayed switching to sex in a facultatively asexual insect

Facultative reproductive strategies that incorporate both sexual and parthenogenetic reproduction should be optimal, yet are rarely observed in animals. Resolving this paradox requires an understanding of the economics of facultative asexuality. Recent work suggests that switching from parthenogenesis to sex can be costly and that females can resist mating to avoid switching. However, it remains unclear whether these costs and resistance behaviors are dependent on female age. We addressed these questions in the Cyclone Larry stick insect, Sipyloidea larryi, by pairing females with males (or with females as a control) in early life prior to the start of parthenogenetic reproduction, or in mid‐ or late life after a period of parthenogenetic oviposition. Young females were receptive to mating even though mating in early life caused reduced fecundity. Female resistance to mating increased with age, but reproductive switching in mid‐ or late life did not negatively affect female survival or offspring performance. Overall, mating enhanced female fitness because fertilized eggs had higher hatching success and resulted in more adult offspring than parthenogenetic eggs. However, female fecundity and offspring viability were also enhanced in females paired with other females, suggesting a socially mediated maternal effect. Our results provide little evidence that switching from parthenogenesis to sex at any age is costly for S. larryi females. However, age‐dependent effects of switching on some fitness components and female resistance behaviors suggest the possibility of context‐dependent effects that may only be apparent in natural populations.     

Sex at the margins: parthenogenesis vs. facultative and obligate sex in a Neotropical ant

Geographic parthenogenesis is a distribution pattern, in which parthenogenetic populations tend to live in marginal habitats, at higher latitudes and altitudes and island‐like habitats compared with the sexual forms. The facultatively parthenogenetic ant Platythyrea punctata is thought to exhibit this general pattern throughout its wide range in Central America and the Caribbean Islands. Workers of P. punctata from the Caribbean produce diploid female offspring from unfertilized eggs by thelytokous parthenogenesis, and mated females and males are rare. In contrast, workers in one colony from Costa Rica were incapable of thelytoky; instead mated workers produced all female offspring. Because sample sizes were very low in former studies, we here use microsatellite markers and explicit tests of thelytoky to examine the population genetic structure of ancestral and derived populations of P. punctata throughout the Caribbean and Central America. Populations from the Caribbean islands were fully capable of parthenogenesis, and population genetic signatures indicate that this is the predominant mode of reproduction, although males are occasionally produced. In contrast, the northernmost population on the mainland (Texas) showed signatures of sexual reproduction, and individuals were incapable of reproduction by thelytoky. Contrary to expectations from a geographic parthenogenesis distribution pattern, most parts of the mainland populations were found to be facultatively thelytokous, with population genetic signatures of both sexual and parthenogenetic reproduction.     

Reduced sexual functionality of PI‐Wolbachia‐infected females of Tetrastichus coeruleus

Wolbachia are endosymbiotic bacteria known to manipulate the reproduction of their hosts by, for example, inducing parthenogenesis. In most cases of Wolbachia‐induced parthenogenesis, the infection is fixed and the entire host population consists of females. In the absence of males and sexual reproduction, genes involved in sexual reproduction are not actively maintained by selection. Accumulation of neutral mutations or selection against maintenance of sexual traits may lead to their loss or deterioration. In addition, females may lose the ability to reproduce sexually due to ‘functional virginity mutations’ that may spread concomitantly with the Wolbachia infection through a population. The parasitoid wasp Tetrastichus coeruleus (Nees) (Hymenoptera: Eulophidae) forms an ideal model to study the decay of sexual functionality, because it has both Wolbachia‐infected, parthenogenetic populations and uninfected, sexual populations. We compared several components of sexual functionality of arrhenotokous (sexual) and thelytokous (parthenogenetic) T. coeruleus females. First, we tested whether arrhenotokous and thelytokous females were equally attractive and receptive to males. Second, we examined whether mating is costly to females by measuring the life span of mated and virgin females. Last, we studied the morphology of the spermathecae of arrhenotokous and thelytokous females. Mated females had shorter life spans than virgin females, showing that mating carried a fitness cost. Two sexual traits of thelytokous females have degraded compared to arrhenotokous females. Arrhenotokous and thelytokous females were equally attractive to males, but thelytokous females were unreceptive to males. Furthermore, there was a clear difference in spermathecal morphology between arrhenotokous and thelytokous females. Our data do not allow distinction between the various potential causes of such degradation. Although the longevity cost of mating may indicate selection against the maintenance of costly sexual traits, accumulation of neutral mutations, functional virginity mutations, manipulation by Wolbachia, and/or the genetic distance between the two populations may all have contributed to the decay of sexual traits in thelytokous females.     

Influence of microbe-associated parthenogenesis on the fecundity ofTrichogramma deion andT. pretiosum

Microbe-associated parthenogenesis (thelytoky) has been discovered in nineTrichogramma species, parasitoids of mainly lepidopteran eggs. Parthenogenetic and bisexual conspecifics co-occur in many field populations. As an initial step to understand the dynamics of these two reproductive strategies we studied the effect of microbe-associated parthenogenesis on fecundity. The fecundity of two parthenogenetic isofemale lines ofT. pretiosum and one ofT. deion was compared with bisexual lines derived from them by antibiotic treatment. In all three cases parthenogenetic females were less fecund over their lifetime than bisexual females. Also, parthenogenetic females produced fewer daughters in two cases and in one case a similar number of daughters as their respective bisexual counterparts. The lack of mating and insemination was excluded as an explanation for the reduced fecundity of parthenogenetic females, because mated and virgin parthenogenetic females produce the same number of offspring. Antibiotic treatment can also be excluded because females of field-collected bisexual line treated with antibiotics produced the same number of offspring as untreated females. The reduced fecundity of parthenogenetic females was caused by a lower number of eggs being laid rather than by a greater developmental mortality. Parthenogenetic females produced less daughters than bisexual females when host availability was not limiting, but when host availability was severely limited, parthenogenetic females produced more daughters than the bisexual females.     

Potential for parthenogenesis of virgin females in a bisexual population of the geographically parthenogenetic mayfly Ephoron shigae (Insecta: Ephemeroptera,Polymitarcyidae)

The burrowing polymitarcyid mayfly Ephoron shigae is a geographically parthenogenetic species. Interestingly, the distributions of the bisexual and unisexual populations overlap broadly in their respective geographic ranges. In this mayfly, obligatory diploid thelytoky appears within unisexual populations. In the present study, we examined the potential for parthenogenesis or the parthenogenetic ability of females in a bisexual population aiming to understand the emergence of unisexual populations. The results obtained revealed that females in the examined bisexual populations showed a potential for diploid thelytoky as also seen in the unisexual populations, although, in females from bisexual populations, the development success rates of their unfertilized eggs were considerably lower than those of virgin females from unisexual populations. In the three bisexual reproducing species (Ephemera japonica, Ephemera strigata, and Ephemera orientalis) in the closely‐related family Ephemeridae, diploid thelytoky (i.e. tychoparthenogenesis; < 3%) was also observed. However, in this case, the parthenogenetic development success rates of unfertilized eggs were significantly lower than those of virgin females in the bisexual (Hino‐yosui Irrigation Canal) population of E. shigae. Accordingly, we suggest that parthenogenetic ability (i.e. tychoparthenogenesis or facultative parthenogenesis) in bisexual populations of E. shigae may facilitate the evolutionary transition to unisexual populations with fully obligatory parthenogenesis. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 99 , 326–334.     

Preadaptation for parthenogenetic colony foundation in subterranean termites Reticulitermes spp. (Isoptera: Rhinotermitidae)

Thelytokous (all-female producing) parthenogenesis, in some cases, involves reproductive advantages against obligate sexual reproduction. However, the completion of parthenogenesis takes multiple steps without the help of males, and thus preadaptation that meets those requirements will be an important factor for the evolution of parthenogenesis. The Japanese subterranean termite, Reticulitermes speratus, is known to have the ability of parthenogenetic colony foundation, where females that failed to mate with males found colonies cooperatively with partner females and reproduce by parthenogenesis. In this study, we compared the parthenogenetic ability and the colony initiation behavior among six Reticulitermes species in Japan. All species other than R. speratus were not able to reproduce parthenogenetically. Nevertheless, females of these species without the parthenogenetic ability performed homosexual female–female colony initiation and produced eggs without fertilization. In addition, in one species without parthenogenetic reproduction, R. kanmonensis, female–female pair initiated founding behavior as quickly as a heterosexual pair. These results suggest that female–female colony initiation and virgin egg-laying are predominant characters among the genus Reticulitermes and provide a preadaptive condition for parthenogenetic colony foundation in R. speratus.     

Life-history changes that accompany the transition from sexual to parthenogenetic reproduction in Drosophila mercatorum

In spite of the predicted genetic and ecological costs of sex, most natural populations maintain sexual reproduction, even those capable of facultative parthenogenesis. Unfertilized eggs from natural populations of Drosophila mercatorum occasionally develop into viable adults, but obligately parthenogenetic populations are unknown in this species. To evaluate the microevolutionary forces that both favor and constrain the evolution of parthenogenesis in D. mercatorum, we have measured parthenogenetic rates across a natural, sexually reproducing population and characterized the life-history changes that accompany the transition from sexual to parthenogenetic reproduction in laboratory strains. A highly significant difference in parthenogenetic rate was found between two populations in close geographic proximity, with increased rate found with lower population density. Laboratory strains of parthenogenetic females suffered increased mortality and reduced egg viability relative to their virgin counterparts from a sexual strain. Lifetime egg production was similar across all strains, but a shift in peak egg production to an earlier age also occurred. The combination of these life-history traits resulted in a higher net reproductive value for sexual females, but because they also had a longer generation time, intrinsic rate of increase was not as dramatically different from parthenogenetic females. In environments with high early mortality, there may be no fitness disadvantage to parthenogenesis, but the predicted ecological advantage of a twofold increase in intrinsic rate of increase was not realized. These results support the theory of Stalker (1956) that parthenogenesis is favored in environments in which sexual reproduction is difficult or impossible.     

Fitness of alternative modes of reproduction: developmental constraints and the evolutionary maintenance of sex

Parthenogenesis, including facultative parthenogenesis, is common among orthopteroid insects. We investigated the fitness associated with sexual and asexual reproduction within a population of the facultatively parthenogenetic cockroach Nauphoeta cinerea. There is significantly reduced fitness for females reproducing parthenogenetically compared to sexually. Fewer than half of all females can reproduce parthenogenetically. In addition, tenfold fewer offspring are produced by parthenogenesis due to reductions in both the number of offspring produced per clutch and the number of clutches produced. Development and brooding of sexually or parthenogenetically produced first instar nymphs does not differ, although the production of the first parthenogenetic clutch is delayed relative to the first sexually produced clutch. The fitness of parthenogens is also lower than the fitness of sexually produced offspring. Parthenogens are less viable than sexually produced offspring even in the benign conditions of the laboratory. Development to adulthood of parthenogens is slower. Fewer parthenogens survive to adulthood and the adult life span of parthenogens is reduced. Individuals produced by parthenogenetic reproduction are unlikely to reproduce parthenogenetically themselves. Finally, parthenogenetically produced females produce fewer offspring by sexual reproduction than do sexually produced females. Since parthenogenetic reproduction is apomictic in N. cinerea and parthenogens are diploid, we suggest that asexual reproduction is developmentally constrained. Once meiosis has evolved, returning to a mitotic mode of reproduction may be difficult. Nauphoeta cinerea offers a system for testing how asexuality is constrained as modes of reproduction can be compared within a facultative parthenogen.     

Novel microsatellite markers suggest the mechanism of parthenogenesis in Extatosoma tiaratum is automixis with terminal fusion

Parthenogenetic reproduction is taxonomically widespread and occurs through various cytological mechanisms, which have different impact on the genetic variation of the offspring. Extatosoma tiaratum is a facultatively parthenogenetic Australian insect (Phasmatodea), in which females oviposit continuously throughout their adult lifespan irrespective of mating. Fertilized eggs produce sons and daughters through sexual reproduction and unfertilized eggs produce female offspring via parthenogenesis. Here, we developed novel microsatellite markers for E. tiaratum and characterized them by genotyping individuals from a natural population. We then used the microsatellite markers to infer the cytological mechanism of parthenogenesis in this species. We found evidence suggesting parthenogenesis in E. tiaratum occurs through automixis with terminal fusion, resulting in substantial loss of microsatellite heterozygosity in the offspring. Loss of microsatellite heterozygosity may be associated with loss of heterozygosity in fitness related loci. The mechanism of parthenogenetic reproduction can therefore affect fitness outcomes and needs to be considered when comparing costs and benefits of sex versus parthenogenesis.     

Androgenesis is a maternal trait in the invasive ant Wasmannia auropunctata

Androgenesis is the production of an offspring containing exclusively the nuclear genome of the fathering male via the maternal eggs. This unusual mating system is generally considered a male trait, giving to androgenetic males a substantial fitness advantage over their sexually reproducing relatives. We here provide the first empirical study of the evolutionary outcomes of androgenesis in a haplo-diploid organism: the invasive ant Wasmannia auropunctata. Some of the populations of this species have a classical haplo-diploid sexual mating system. In other populations, females and males are produced through parthenogenesis and androgenesis, respectively, whereas workers are produced sexually. We conducted laboratory reciprocal-cross experiments with reproductive individuals from both types of populations and analysed their progenies with genetic markers, to determine the respective contribution of males and females to the production of androgenetic males. We found that androgenesis was a parthenogenetic female trait. A population genetic study conducted in natura confirmed the parthenogenetic female origin of androgenesis, with the identification of introgression events of sexual male genotypes into androgenetic/parthenogenetic lineages. We argue that by producing males via androgenesis, parthenogenetic queen lineages may increase and/or maintain their adaptive potential, while maintaining the integrity of their own genome, by occasionally acquiring new male genetic material and avoiding inbreeding depression within the sexually produced worker cast.     

Antibiotic curing of parthenogenesis in Eretmocerus mundus (Australian parthenogenic form)

The thelytokous parasitoid, Eretmocerus mundus (Australian parthenogenetic form) was infected with a species of Group B Wolbachia. Antibiotic treatment of the parasitoid cured parthenogenesis and lead to male production and reduced egg hatching by virgin females. For each generation infected females produced more progeny than cured females. The descendants of individuals treated with antibiotic were in most cases free of a detectable infection. Both treated females and descendant females mated and received sperm, but these were not used as mated and unmated cured females produced offspring with a similar sex ratio. Males produced as a result of the antibiotic treatment were at least partially functional as they produced sperm and copulated with and inseminated females. However, no sexual line could be established.     

Loss and gain of sexual reproduction in the same stick insect

The outcome of competition between different reproductive strategies within a single species can be used to infer selective advantage of the winning strategy. Where multiple populations have independently lost or gained sexual reproduction it is possible to investigate whether the advantage is contingent on local conditions. In the New Zealand stick insect Clitarchus hookeri, three populations are distinguished by recent change in reproductive strategy and we determine their likely origins. One parthenogenetic population has established in the United Kingdom and we provide evidence that sexual reproduction has been lost in this population. We identify the sexual population from which the parthenogenetic population was derived, but show that the UK females have a post‐mating barrier to fertilisation. We also demonstrate that two sexual populations have recently arisen in New Zealand within the natural range of the mtDNA lineage that otherwise characterizes parthenogenesis in this species. We infer independent origins of males at these two locations using microsatellite genotypes. In one population, a mixture of local and nonlocal alleles suggested males were the result of invasion. Males in another population were most probably the result of loss of an X chromosome that produced a male phenotype in situ. Two successful switches in reproductive strategy suggest local competitive advantage for outcrossing over parthenogenetic reproduction. Clitarchus hookeri provides remarkable evidence of repeated and rapid changes in reproductive strategy, with competitive outcomes dependent on local conditions.     

Retention of Ejaculate by Drosophila melanogaster Females Requires the Male-Derived Mating Plug Protein PEBme

Within the mated reproductive tracts of females of many taxa, seminal fluid proteins (SFPs) coagulate into a structure known as the mating plug (MP). MPs have diverse roles, including preventing female remating, altering female receptivity postmating, and being necessary for mated females to successfully store sperm. The Drosophila melanogaster MP, which is maintained in the mated female for several hours postmating, is comprised of a posterior MP (PMP) that forms quickly after mating begins and an anterior MP (AMP) that forms later. The PMP is composed of seminal proteins from the ejaculatory bulb (EB) of the male reproductive tract. To examine the role of the PMP protein PEBme in D. melanogaster reproduction, we identified an EB GAL4 driver and used it to target PEBme for RNA interference (RNAi) knockdown. PEBme knockdown in males compromised PMP coagulation in their mates and resulted in a significant reduction in female fertility, adversely affecting postmating uterine conformation, sperm storage, mating refractoriness, egg laying, and progeny generation. These defects resulted from the inability of females to retain the ejaculate in their reproductive tracts after mating. The uncoagulated MP impaired uncoupling by the knockdown male, and when he ultimately uncoupled, the ejaculate was often pulled out of the female. Thus, PEBme and MP coagulation are required for optimal fertility in D. melanogaster. Given the importance of the PMP for fertility, we identified additional MP proteins by mass spectrometry and found fertility functions for two of them. Our results highlight the importance of the MP and the proteins that comprise it in reproduction and suggest that in Drosophila the PMP is required to retain the ejaculate within the female reproductive tract, ensuring the storage of sperm by mated females.     

EFFECTS OF PARTHENOGENESIS AND GEOGRAPHIC ISOLATION ON FEMALE SEXUAL TRAITS IN A PARASITOID WASP

Population divergence in sexual traits is affected by different selection pressures, depending on the mode of reproduction. In allopatric sexual populations, aspects of sexual behavior may diverge due to sexual selection. In parthenogenetic populations, loss‐of‐function mutations in genes involved in sexual functionality may be selectively neutral or favored by selection. We assess to what extent these processes have contributed to divergence in female sexual traits in the parasitoid wasp Leptopilina clavipes in which some populations are infected with parthenogenesis‐inducing Wolbachia bacteria. We find evidence consistent with both hypotheses. Both arrhenotokous males and males derived from thelytokous strains preferred to court females from their own population. This suggests that these populations had already evolved population‐specific mating preferences when the latter became parthenogenetic. Thelytokous females did not store sperm efficiently and fertilized very few of their eggs. The nonfertility of thelytokous females was due to mutations in the wasp genome, which must be an effect of mutation accumulation under thelytoky. Divergence in female sexual traits of these two allopatric populations has thus been molded by different forces: independent male/female coevolution while both populations were still sexual, followed by female‐only evolution after one population switched to parthenogenesis.     

Population variation and ecological correlates of tychoparthenogenesis in the mayfly, Stenonema femoratum

Species in which both sex and parthenogenesis co‐occur are extremely valuable for investigating ecological conditions favouring sex. Tychoparthenogenesis is a breeding system characterized by hatching of a small proportion of unfertilized eggs (typically < 10%) from females of sexually reproducing species. With tychoparthenogenesis, both sexual and parthenogenetic reproduction co‐occur within the same population. To identify ecological conditions that may favour this breeding system, I quantified population variation in females’ capacity for tychoparthenogenesis and investigated biotic and abiotic correlates of tychoparthenogenesis. I estimated tychoparthenognetic capacity (proportion of unfertilized eggs hatching) for females from 12 Missouri populations of the mayfly, Stenonema femoratum (Ephemeroptera: Heptageniidae), across three different habitat types – temporary streams, permanent streams and lakes. Tychoparthenogenetic capacity, measured as the population mean hatch success of unfertilized eggs, ranged from 3.8 to 10.7%. Tychoparthenogenetic capacity varied among habitats in 1996, but not in 1997. In 1996, temporary streams showed hatch success of unfertilized eggs twice that of permanent streams and lakes. Tychoparthenogenetic capacity also varied among sampling dates within years. Temporary streams also showed extremely low nymph densities compared to the other two habitats. However, habitats did not differ in adult density. Furthermore, in all populations nymphs showed significantly female‐biased sex ratios. In contrast, adult sex ratios were equal or slightly male biased. Tychoparthenogenetic capacity was negatively correlated with nymph density in 1996, but not in 1997, suggesting possible reproductive assurance in some years. Adult densities also suggested that there may be certain times of year when tychoparthenogenesis may provide benefits of reproductive assurance. Although habitats differed significantly in their abiotic characteristics, tychoparthenogenetic capacity was correlated significantly with water temperature only. © 2002 The Linnean Society of London, Biological Journal of the Linnean Society, 2002, 75 , 101–123.     

Exploring the relationship between tychoparthenogenesis and inbreeding depression in the Desert Locust,Schistocerca gregaria

Tychoparthenogenesis, a form of asexual reproduction in which a small proportion of unfertilized eggs can hatch spontaneously, could be an intermediate evolutionary link in the transition from sexual to parthenogenetic reproduction. The lower fitness of tychoparthenogenetic offspring could be due to either developmental constraints or to inbreeding depression in more homozygous individuals. We tested the hypothesis that in populations where inbreeding depression has been purged, tychoparthenogenesis may be less costly. To assess this hypothesis, we compared the impact of inbreeding and parthenogenetic treatments on eight life‐history traits (five measuring inbreeding depression and three measuring inbreeding avoidance) in four laboratory populations of the desert locust, Schistocerca gregaria, with contrasted demographic histories. Overall, we found no clear relationship between the population history (illustrated by the levels of genetic diversity or inbreeding) and inbreeding depression, or between inbreeding depression and parthenogenetic capacity. First, there was a general lack of inbreeding depression in every population, except in two populations for two traits. This pattern could not be explained by the purging of inbreeding load in the studied populations. Second, we observed large differences between populations in their capacity to reproduce through tychoparthenogenesis. Only the oldest laboratory population successfully produced parthenogenetic offspring. However, the level of inbreeding depression did not explain the differences in parthenogenetic success between all studied populations. Differences in development constraints may arise driven by random and selective processes between populations.     

Flying the nest: male dispersal and multiple paternity enables extrafamilial matings for the invasive bark beetle Dendroctonus micans

There is an evolutionary trade-off between the resources that a species invests in dispersal versus those invested in reproduction. For many insects, reproductive success in patchily-distributed species can be improved by sibling-mating. In many cases, such strategies correspond to sexual dimorphism, with males–whose reproductive activities can take place without dispersal–investing less energy in development of dispersive resources such as large body size and wings. This dimorphism is particularly likely when males have little or no chance of mating outside their place of birth, such as when sperm competition precludes successful fertilisation in females that have already mated. The economically important bark beetle pest species Dendroctonus micans (Coleoptera: Curculionidae, Scolytinae) has been considered to be exclusively sibling-mating, with 90% of females having already mated with their brothers by emergence. The species does not, however, show strong sexual dimorphism; males closely resemble females, and have been observed flying through forests. We hypothesised that this lack of sexual dimorphism indicates that male D. micans are able to mate with unrelated females, and to sire some or all of their offspring, permitting extrafamilial reproduction. Using novel microsatellite markers, we carried out cross-breeding laboratory experiments and conducted paternity analyses of resulting offspring. Our results demonstrate that a second mating with a less-related male can indeed lead to some offspring being sired by the latecomer, but that most are sired by the first, sibling male. We discuss these findings in the context of sperm competition versus possible outbreeding depression.     

Genetic evidence for the mating system and reproductive success of black sea bream (Acanthopagrus schlegelii)

Understanding the mating system and reproductive success of a species provides evidence for sexual selection. We examined the mating system and the reproductive success of captive adult black sea bream (Acanthopagrus schlegelii), using parentage assignment based on two microsatellites multiplex PCR systems, with 91.5% accuracy in a mixed family (29 sires, 25 dams, and 200 offspring). Based on the parentage result, we found that 93.1% of males and 100% of females participated in reproduction. A total of 79% of males and 92% of females mated with multiple partners (only 1 sire and 1 dam were monogamous), indicating that polygynandry best described the genetic mating system of black sea bream. For males, maximizing the reproductive success by multiple mating was accorded with the sexual selection theory while the material benefits hypothesis may contribute to explain the multiple mating for females. For both sexes, there was a significant correlation between mating success and reproductive success and the variance in reproductive success of males was higher than females. Variation in mating success is the greatest determinant to variation in reproductive success when the relationship is strongly positive. The opportunity for sexual selection of males was twice that of females, as well as the higher slope of the Bateman curve in males suggested that the intensity of intrasexual selection of males was higher than females. Thus, male–male competition would lead to the greater variation of mating success for males, which caused greater variation in reproductive success in males. The effective population number of breeders (N_b) was 33, and the N_b/N ratio was 0.61, slightly higher than the general ratio in polygynandrous fish populations which possibly because most individuals mated and had offspring with a low variance. The relatively high N_b contributes to the maintenance of genetic diversity in farmed black sea bream populations.     

Influence of male mating history on female reproductive success among monandrous Naryciinae (Lepidoptera: Psychidae)

1. Multiple male copulations can have detrimental effects on female fitness due to sperm limitation. 2. Monandrous Naryciinae females are immobile while the males are short‐lived and do not feed. Multiple male mating is therefore expected to lead to sperm limitation in females. Sperm limitation and male limitation are hypothesised as causes of the repeated evolution of parthenogenetic reproduction in the Psychidae. 3. In this study, the effects of multiple male mating on female reproduction are investigated in several species of Naryciinae by allowing males multiple copulations. The results for two species, Siederia listerella and Dahlica lichenella, are compared. The sex ratios of 53 natural populations are examined for indications of male limitation. 4. Previous copulations by the male increased the female's risk of remaining unfertilised. However, contrary to expectations, those unfertilised females were capable of successful re‐mating. 5. In S. listerella, the number of previous copulations of males negatively influenced female fitness. Females produced 30% fewer offspring if they mated with a previously mated male. In D. lichenella, the older the male and the lower its number of total lifetime copulations, the higher the female's reproductive success. 6. Only a fraction of the investigated populations had a female‐skewed sex ratio, but differences in development time between males and females could lead to reproductive asynchrony. 7. In conclusion, male mating history did not lead to strong sperm limitation in Naryciinae as had been suggested by their life history.