Size- and density-dependent reproductive success of bagworms, Metisa plana

A study conducted in a Malaysian plantation of oil palm over 5 consecutive generations of bagworms, Metisa plana (Walker) (Lepidoptera: Psychidae), evaluated extent and causes of variability for 3 components of reproductive success: pupal mortality, mating success and fecundity. The population of M. plana in the experimental site exhibited cycles of 70–80 days with discrete generations. Females emerged before males during all generations. Relatively large proportions of M. plana did not reproduce, either because they did not survive as pupa or (for females) mate as adult. Occurrence of unmated female bagworms may be attributed to complex mating procedure, short lifespan of females, limited mating capacity of males, protogyny inducing female-biased operational sex-ratio, and/or flightlessness per se constraining mating success of females. Size attained at pupation is a significant component of reproductive success, with large individuals having greatest survival during pupal stage, mating success and fecundity. Population density also influenced reproductive success of M. plana: female and (to a lesser extent) male larvae on crowded palms attained small size at pupation; survival of pupae was density-dependent during 2 generations for females and density-independent during 5 generations for males; mating success of females was inverse density-dependent during 4 generations. Size- and density-dependent mating success of females may be attributed to mate choice by males, size-dependent pheromone production by and longevity of females, and/or disorientation of mate-seeking males around heavily infested palms. Long-term studies are needed to determine whether and to what extent attributes of oil palm, seasonal fluctuations of abiotic factors and inter-generational variations of reproductive success influence population dynamics of M. plana.     

Mating Behavior of Trissolcus basalis (Wollaston) (Hymenoptera: Scelionidae): Potential for Outbreeding in a Predominantly Inbreeding Species

The mating behavior of the quasi-gregarious egg parasitoid Trissolcus basalis (Wollaston) was investigated under field conditions. Trissolcus basalis has female-biased sex ratios and is a protandrous species, with males emerging 1–2 days before females. Males competed aggressively for control of the egg mass, with one male assuming dominance and control of the egg mass, although changes in dominance occurred at least once on each egg mass observed. Typical mating behavior involved the dominant male mating his sisters immediately upon their emergence from the egg mass. These behaviors are characteristic of an inbreeding species that manifests local mate competition. However, several aspects of the mating behavior of T. basalis are inconsistent with that of an inbreeding species. Over 18% of emerging females were not mated by the dominant male upon emergence, 13% of females were not observed to be mated at all and may have left their natal site as virgins, 25% of females were mated multiple times and sometimes by multiple males, females remained near the natal site for up to several hours after emergence before emigrating, and males dispersed away from the natal site during female emergence. Trissolcus basalis may be a predominantly inbreeding species but its emergence and mating behavior suggest that low-frequency outbreeding is also likely to occur.     

Dynamics of mating success in experimental groups ofDrosophila melanogaster (Diptera: Drosophilidae)

Determinants of male courtship success in Drosophila melanogasterwere examined in groups of five males sequentially presented with five individual females. Thirty-three percent of males never mated, while approximately half of the males mated two or three times. Rapid courtship initiation was associated with male success in early matings only. Male size was important for courtship outcome, but the size distributions of mating and nonmating males and their progeny numbers indicate balancing rather than directional selection on size- dependent courtship success.     

Polyandrous females acquire indirect benefits in a nuptial feeding species

The relative force of direct and indirect selection underlying the evolution of polyandry is contentious. When females acquire direct benefits during mating, indirect benefits are often considered negligible. Although direct benefits are likely to play a prominent role in the evolution of polyandry, post‐mating selection for indirect benefits may subsequently evolve. We examined whether polyandrous females acquire indirect benefits and quantified direct and indirect effects of multiple mating on female fitness in a nuptial gift‐giving spider (Pisaura mirabilis). In this system, the food item donated by males during mating predicts direct benefits of polyandry. We compared fecundity, fertility and survival of singly mated females to that of females mated three times with the same (monogamy) or different (polyandry) males in a two‐factorial design where females were kept under high and low feeding conditions. Greater access to nutrients and sperm had surprisingly little positive effect on fitness, apart from shortening the time until oviposition. In contrast, polyandry increased female reproductive success by increasing the probability of oviposition, and egg hatching success indicating that indirect benefits arise from mating with several different mating partners rather than resources transferred by males. The evolution of polyandry in a male‐resource‐based mating system may result from exploitation of the female foraging motivation and that indirect genetic benefits are subsequently derived resulting from co‐evolutionary post‐mating processes to gain a reproductive advantage or to counter costs of mating. Importantly, indirect benefits may represent an additional explanation for the maintenance of polyandry.     

Female Remating Behavior in a Lekking Moth

In polyandrous species, male reproductive success will at least partly be determined by males' success in sperm competition. To understand the potential for post‐mating sexual selection, it is therefore important to assess the extent of female remating. In the lekking moth Achroia grisella, male mating success is strongly determined by female choice based on the attractiveness of male ultrasonic songs. Although observations have indicated that some females will remate, only little is known about the level of sperm competition. In many species, females are more likely to remate if their first mating involved an already mated male than if the first male was virgin. Potentially, this is because mated males are less well able to provide an adequate sperm supply, nutrients, or substances inhibiting female remating. This phenomenon will effectively reduce the strength of pre‐copulatory sexual selection because attractive males with high mating success will be more susceptible to sperm competition. We therefore performed an experiment designed both to provide a more precise estimate of female remating probability and simultaneously to test the hypothesis that female remating is influenced by male mating history. Overall, approximately one of five females remated with a second male. Yet, although females mated to non‐virgin males were somewhat more prone to remate, the effect of male mating history was not significant. The results revealed, however, that heavier females were more likely to remate. Furthermore, we found that females' second copulations were longer, suggesting that, in accordance with theory, males may invest more sperm in situations with an elevated risk of sperm competition.     

Pre‐ and postcopulatory sexual selection favor aggressive,young males in polyandrous groups of red junglefowl

A challenge in evolutionary biology is to understand the operation of sexual selection on males in polyandrous groups, where sexual selection occurs before and after mating. Here, we combine fine‐grained behavioral information (>41,000 interactions) with molecular parentage data to study sexual selection in replicated, age‐structured groups of polyandrous red junglefowl, Gallus gallus. Male reproductive success was determined by the number of females mated (precopulatory sexual selection) and his paternity share, which was driven by the polyandry of his female partners (postcopulatory sexual selection). Pre‐ and postcopulatory components of male reproductive success covaried positively; males with high mating success also had high paternity share. Two male phenotypes affected male pre‐ and postcopulatory performance: average aggressiveness toward rival males and age. Aggressive males mated with more females and more often with individual females, resulting in higher sexual exclusivity. Similarly, younger males mated with more females and more often with individual females, suffering less intense sperm competition than older males. Older males had a lower paternity share even allowing for their limited sexual exclusivity, indicating they may produce less competitive ejaculates. These results show that—in these populations—postcopulatory sexual selection reinforces precopulatory sexual selection, consistently promoting younger and more aggressive males.     

FEMALES RECEIVE A LIFE-SPAN BENEFIT FROM MALE EJACULATES IN A FIELD CRICKET

Abstract.— Mating has been found to be costly for females of some species because of toxic products that males transfer to females in their seminal fluid. Such mating costs seem paradoxical, particularly for species in which females mate more frequently than is necessary to fertilize their eggs. Indeed, some studies suggest that females may benefit from mating more frequently. The effect of male ejaculates on female life span and lifetime fecundity was experimentally tested in the variable field cricket, Gryllus lineaticeps. In field crickets, females will mate repeatedly with a given male and mate with multiple males. Females that were experimentally mated either repeatedly or multiply lived more than 32% longer than singly mated females. In addition, multiply mated females produced 98% more eggs than singly mated females. Because females received only sperm and seminal fluid from males in the experimental matings, these life‐span and fecundity benefits may result from beneficial seminal fluid products that males transfer to females during mating. Mating benefits rather than mating costs may be common in many animals, particularly in species where female mate choice has a larger effect on male reproductive success than does the outcome of sperm competition.     

Female prereproductive coloration reduces mating harassment in damselflies

Conspicuous female coloration can evolve through male mate choice or via female-female competition thereby increasing female mating success. However, when mating is not beneficial, such as in pre-reproductive females, selection should favor cryptic rather than conspicuous coloration to avoid male detection and the associated harassment. Nevertheless, conspicuous female coloration occurs in many prereproductive animals, and its evolution remains an enigma. Here, I studied conspicuous female coloration in Agriocnemis femina damselflies, in which the conspicuous red color of the immature females changes to a less conspicuous green approximately a week after their emergence. I measured body size, weight, and egg numbers of the female morphs and found that red females are smaller and lighter and do not carry developed eggs. Finally, I calculated the occurrence frequency and mating frequency of red and green females in several populations over a three-year period. The results demonstrate that red females mated less frequently than green females even when red females were the abundant morph in the populations. I concluded that conspicuous female coloration is likely to function as a warning signal of sexual unprofitability, thereby reducing sexual harassment for females and unprofitable mating for males.     

Effects of multiple matings on reproductive fitness of male and female Diaeretiella rapae

Mating frequency and the amount of sperm transferred during mating have important consequences on progeny sex ratio and fitness of haplodiploid insects. Production of female offspring may be limited by the availability of sperm for fertilizing eggs. This study examined multiple mating and its effect on fitness of the cabbage aphid parasitoid Diaeretiella rapae McIntosh (Hymenoptera: Aphidiidae). Female D. rapae mated once, whereas males mated with on average more than three females in a single day. The minimum time lag between two consecutive matings by a male was 3 min, and the maximum number of matings a male achieved in a day was eight. Sperm depletion occurred as a consequence of multiple mating in D. rapae. The number of daughters produced by females that mated with multiple‐mated males was negatively correlated with the number of matings achieved by these males. Similarly, the proportion of female progeny decreased in females that mated with males that had already mated three times. Although the proportion of female progeny resulting from multiple mating decreased, the decrease was quicker when the mating occurred on the same day than when the matings occurred once per day over several days. Mating success of males initially increased after the first mating, but then males became ‘exhausted’ in later matings; their mating success decreased with the number of prior matings. The fertility of females was affected by mating with multiple‐mated males. The study suggests that male mating history affects the fitness of male and female D. rapae.     

Mating order-dependent female mate choice in the polygynandrous common lizard Lacerta vivipara

Recent studies indicate that directional female mate choice and order-dependent female mate choice importantly contribute to non-random mating patterns. In species where females prefer larger sized males, disentangling different hypotheses leading to non-random mating patterns is especially difficult, given that male size usually correlates with behaviours that may lead to non-random mating (e.g. size-dependent emergence from hibernation, male fighting ability). Here we investigate female mate choice and order-dependent female mate choice in the polygynandrous common lizard (Lacerta vivipara). By sequentially presenting males in random order to females, we exclude non-random mating patterns potentially arising due to intra-sexual selection (e.g. male–male competition), trait-dependent encounter probabilities, trait-dependent conspicuousness, or trait-dependent emergence from hibernation. To test for order-dependent female mate choice we investigate whether the previous mating history affects female choice. We show that body size and body condition of the male with which a female mated for the first time were bigger and better, respectively, than the average body size and body condition of the rejected males. There was a negative correlation between body sizes of first and second copulating males. This indicates that female mate choice is dependent on the previous mating history and it shows that the female’s choice criteria are non-static, i.e. non-directional. Our study therefore suggests that context-dependent female mate choice may not only arise due to genotype-environment interactions, but also due to other female mating strategies, i.e. order-dependent mate choice. Thus context-dependent female mate choice might be more frequent than previously thought.     

Multiple Mating Increases Fecundity, Fertility and Relative Clutch Mass in the Female Leopard Gecko (Eublepharis macularius)

Females across many taxa may mate with several males or mate more than once with the same male within one reproductive event. Although many researchers have discussed the effects of multiple mating on reproductive success of females, few studies have attempted to disentangle whether the reproductive success of females differs with respect to whether females mate with multiple males or mate more than once with one male. In this study, we hypothesized that female leopard geckos (Eublepharis macularius) increase aspects of their reproductive success, such as fecundity, fertility and relative clutch mass, by mating more than once within one reproductive event, either by mating repeatedly with the same male or multiply mating with different males. We controlled for the potentially confounding variables of mating frequency and mate number by allowing females to mate once with one male, twice with the same male, or twice with two different males. We found that females that mated with more than one male laid more clutches, exhibited increased egg fertility and invested more in clutches relative to females that mated only once with one male, whereas females that mated twice to the same male were intermediate for these variables. Thus, reproductive success is higher among female leopard geckos that mated with more than one male compared to female leopard geckos that mated only once.     

Mating frequency and reproductive success in an income breeding moth,Mnesampela privata

The frequency of mating in insects is often an important determinant of female reproductive output and male sperm competition. In Lepidoptera that provide male nutrients to the female when mating, it is hypothesized that polyandry may be more prevalent. This is thought to be especially so among species described as income breeders; that is, in species who do not derive all their nutrients for reproductive output entirely from the resources obtained during the larval stage. We selected the geometrid moth, Mnesampela privata (Guenée) (Lepidoptera: Geometridae), to examine this hypothesis further. We found this species was best characterized as an income breeder with female weight on emergence positively correlated with total egg load but not with the number of eggs laid. Further, in accord with income breeders, females emerged with a partially developed egg load and lifetime fecundity was positively correlated with the number of oviposition days. However, in the laboratory we found that incidence of repeated matings or polyandry was rare. When moths were paired singly over their lifetime, only 4% of mated females multiple mated. When females were paired with three males concurrently, female mating success increased from 60 to 81% with multiple mating among mated females increasing to just 15%. Dissection of wild caught M. privata found that polyandry levels were also low with a maximum of 16.4% of females collected at any one time being multiple mated. In accord with theory, mating significantly increased the longevity of females, but not of males, suggesting that females acquire essential resources from male ejaculates. Despite this, multiple mated females showed a trend toward decreasing rather than increasing female reproductive output. Spermatophore size, measured on death of the female, was not correlated with male or female forewing length but was negatively correlated with the number of fertile eggs laid and female longevity. Smaller spermatophore width may be related to uptake of more nutrients by the female from a spermatophore. We discuss our findings in relation to income breeding and its relationship to polyandry in Lepidoptera.     

Is egg carrying attractive? Mate choice in the golden egg bug (Coreidae,Heteroptera)

In several species of fish, females select males that are already guarding eggs in their nests. It is a matter of debate as to whether a female selects a good nest site for her offspring (natural selection) or a male for his attractiveness (sexual selection). The golden egg bug, Phyllomorpha laciniata Vill, resembles fish in the sense that mating males carry more eggs than single males, but in the bugs, female mate choice is decoupled from egg site choice. The sexual selection hypothesis predicts that if females select males using male egg load as a cue for male quality, they should not mate with a male when eggs are removed, regardless of his mating attempts. When individual females were enclosed with an egg-loaded male and an unloaded male, they mated equally often with both males, although the loaded males courted more. In addition, when only successful males were used, females mated equally often with the loaded male and the unloaded male irrespective of sex ratio. Male choice rather than female choice affected mating frequency when sex ratio was equal. Therefore, females do not select the male by the eggs he carries, but successful males may receive many eggs due to egg dumping by alien females while they mate or as a consequence of mate guarding.     

The Starling Mating System as an Outcome of the Sexual Conflict

Many bird species demonstrate a variable mating system, with some males being monogamously mated and other males able to attract more than one mate. This variation in avian mating systems is often explained in terms of potential costs of sharing breeding partners and compensation for such costs. However, whenever there is a difference in the optimal mating system for males and females, a sexual conflict over the number of partners is expected. This paper contains a verbal model of how a conflict between male and female European starlings (Sturnus vulgaris),resulting from the fitness consequences of different mating systems for males and females differing over time, determines the mating system. We demonstrate that males and females have contrasting fitness interests regarding mating system, such that males gain from attracting additional mates whereas already mated females pay a cost in terms of reduced reproductive success if males are successful in attracting more mates. We demonstrate how this can be traced to the rules by which males allocate non-sharable care between different broods. Furthermore, we demonstrate that there exist male and female conflict behaviours with the potential to affect the mating system. For example, aggression from already mated females towards prospecting females can limit male mating success and males can circumvent this by spacing the nest-sites they defend. The realised mating system will emerge as a consequence of both the fitness value of the different mating systems for males and females, and the costs for males and females of intersexual competition. We discuss how this model can be developed and critically evaluated in the future.     

Female mating success and risk of pre-reproductive death in a protandrous grasshopper

Numerous studies have assessed the adaptive value of protandry for males in several insect species, considering that male emergence is determined by female availability. However, the possible advantage of the time of emergence for females on their mating success in protandrous insect species has only been explored theoretically. By studying the grasshopper Sphenarium purpurascens we evaluated the hypothesis that late emergence could be adaptive for females. If female maturation occurs when the population density is higher and the sex ratio (males/females) is biased to males, their probability of mating increases. Thus, in this study we estimated (1) the opportunity for mating in females as a function of their sexual maturation time, population density, and sex ratio at the moment they reached sexual maturity. In addition, (2) an analysis incorporating female body size and the total number of female matings was performed. Both analyses support the occurrence of protandry in the studied population. Under the first approach, females with intermediate maturation time had a higher probability of being mated than earlier and late matured females. Thus, it suggests that stabilising selection is acting on female maturation time and this may affect selection on male maturation time. Furthermore, the proportion of mated females increased when the sex ratio was biased to males, and stabilising selection on maturation time was detected also. However, the number of matings of a female depended on her body size. Females with larger body size had more matings than smaller ones at the beginning of the reproductive season. Because selection acts differently on maturation time in males and females of S. purpurascens this result is consistent with a condition for the maintenance of protandry in the population. The present results are discussed in the light of the models for the evolution of protandry.     

Mating Frequency, Fecundity and Fertilization Success in the Hide Beetle, Dermestes Maculatus

While the immediate benefits accrued to females through multiple mating are well documented, the effect of sperm depletion for multiply mating males is rarely considered. We show that, in small mixed-sex laboratory aggregations, both male and female hide beetles, Dermestes maculatus (De Geer) mated multiply. There was considerable variation in the mating frequency of both sexes; however the skew in mating success was comparable for males and females. Several individuals that mated multiply also re-mated with a previous partner, but in a competitive environment no male copulated more than seven times. Mating success was unrelated to an individual's size, but males that had the most inter-sexual matings also engaged in the most intra-sexual mating attempts. In a second experiment, we show that, even in the absence of rivals, only a small number of males mated with all available virgin females. Moreover, even though males were mated twice to each female, males that copulated more than eight times failed to fertilize any eggs. We suggest that under natural conditions male hide beetles may refrain from mating either prior to, or at the point of, sperm depletion thereby reducing the selection pressure for females to discriminate against sperm depleted males. However, fecundity and fertilization success varied considerably across females and even those mating with sperm-replete males were unable to fertilize 100% of their egg batch. Thus, direct fertilization benefits accrued by females through mating more than once with the same male may play a key role in the maintenance of polyandry in this species.     

Effects of size at metamorphosis on stonefly fecundity, longevity, and reproductive success

Many organisms with complex life cycles show considerable variation in size and timing at metamorphosis. Adult males of Megarcyssignata (Plecoptera: Perlodidae) are significantly smaller than females and emerge before females (protandry) from two western Colorado streams. During summer 1992 stoneflies from a trout stream emerged earlier in the season and at larger sizes than those from a colder fishless stream, and size at metamorphosis did not change over the emergence period in either stream. We performed two experiments to determine whether variation in size at metamorphosis affected the fecundity, reproductive success and longevity of individuals of this stonefly species and if total lifetime fecundity was affected by the number of matings. In the first experiment, total lifetime fecundity (eggs oviposited) was determined for adult females held in small plastic cages in the field. Males were removed after one copulation, or pairs were left together for life and allowed to multiply mate. Most copulations occurred in the first few days of the experiment. Females in treatments allowing multiple matings had significantly lower total lifetime fecundity and shorter adult longevity than females that only mated once. Multiple matings also reduced longevity of males. Fecundity increased significantly with female body mass at emergence, but only for females that mated once. While multiple matings eliminated the fecundity advantage of large female body size, number of matings did not affect the significant positive relationship between body mass at metamorphosis and longevity of males or females. In a second experiment designed to determine if body mass at emergence affected male mating success, we placed one large and one small male Megarcys in an observation arena containing one female and recorded which male obtained the first mating. The large and the small male had equal probabilities of copulating with the female. Copulations usually lasted all night, and the unmated male made frequent, but unsuccessful attempts to take over the copulating female. Our data suggest that selection pressures determining body size at metamorphosis may operate independently on males and females, resulting in evolution of sexual size dimorphism, protandry, and mating early in the adult stage. We emphasize the importance of interpreting the fitness consequences of larval growth and development on the timing of and size at metamorphosis in the context of the complete life cycle. Received: 1 July 1997 / Accepted: 12 November 1997     

Reduction in the attraction of males to females after mating in the rice leaf bug Trigonotylus caelestialium

The influence of mating on the extent to which males are attracted to females in Trigonotylus caelestialium (Heteroptera: Miridae) was examined. No differences in attraction of males to mated and virgin females were observed within 3–5 h of mating, but males became less attracted to females 1 to 2 days after the first mating. The difference in male attraction to mated vs virgin females disappeared at 4 days after mating. These results indicate that reduced attraction of males to mated females occurs after a certain time interval, and persists for a few days. Furthermore, males were less attracted to females that had mated with virgin vs recently mated males, i.e. males that had just mated with another female at 1 and 2 days after mating. The ejaculate expenditure of recently mated males was less than that of virgin males. Hence, the amount of male ejaculate transferred to females during mating, rather than the act of mating, might influence the attraction of males to females. The results demonstrate that mating reduces the attraction of males to females in T. caelestialium on the basis of direct observation of male behavior.     

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.     

Mating behavior and male mating success in wildAnastrepha Ludens (Diptera: Tephritidae) on a field-caged host tree

Mating behavior and factors affecting mating success of males were studied using wild Anastrepha ludens on a fieldcaged host tree. The most common courtship sequence had five components: (1) male calls from the underside of a leaf, (2) female arrives to the maleoccupied leaf, (3) male orients to female and stops calling, (4) one or both approach to a face-to-face position 1–3 cm apart, and (5) male mounts female after 1–2 s. Courtship behavior was almost identical to that of laboratoryculture flies observed previously under laboratory conditions. Most malefemale encounters occurred at a height of 1–2m, well inside the outer canopy of the tree. Differential mating success by males occurred. No male mated more than once per day, owing possibly to a very short sexual activity period. Factors favoring mating success of males were survival ability and tendency to join male aggregations and to fight other males. Thorax length and age (9–11 days difference) had no effects on male copulatory success. Overall win/loss percentage was not related to mating success because the males that were most successful at mating fought mostly among themselves, driving their win/loss percentage down. However, these successful males (at mating) won most of their fights against less successful males. Results confirmed a lek mating system: males aggregated, called, and defended territories; territories did not contain femalerequired resources; and females exercised mate choice, apparently through selection of sites within leks.