Variation in the male pheromones and mating success of wild caught Drosophila melanogaster

Drosophila melanogaster males express two primary cuticular hydrocarbons (male-predominant hydrocarbons). These act as sex pheromones by influencing female receptivity to mating. The relative quantities of these hydrocarbons vary widely among natural populations and can contribute to variation in mating success. We tested four isofemale lines collected from a wild population to assess the effect of intrapopulation variation in male-predominant hydrocarbons on mating success. The receptivity of laboratory females to males of the four wild-caught lines varied significantly, but not consistently in the direction predicted by variation in male-predominant hydrocarbons. Receptivity of the wild-caught females to laboratory males also varied significantly, but females from lines with male-predominant hydrocarbon profiles closer to a more cosmopolitan one did not show a correspondingly strong mating bias toward a cosmopolitan male. Among wild-caught lines, the male-specific ejaculatory bulb lipid, cis-vaccenyl acetate, varied more than two-fold, but was not associated with variation in male mating success. We observed a strong inverse relationship between the receptivity of wild-caught females and the mating success of males from their own lines, when tested with laboratory flies of the opposite sex.     

Mating success of wild type and sepia mutants Drosophila melanogaster in different choice.

Mating behaviour of red-eyed (wt) and brown-eyed (sepia) Drosophila melanogaster was studied under light conditions. Mating success was directly observed in mating vials and techniques usually applied in the studies of sexual selection ("female choice" and "multiple choice"). The comparison of sexual activity of mutant and wild types clearly indicates that they are not equally successful in matings. Sepia eye colour mutation decreases sexual activity of Drosophila melanogaster males, influences the preference ability of females and decreases the number of progeny from homogamic mating of the se x se type, as well as from heterogamic copulations in which sepia females take part. Non-random mating of wild type males and sepia females (in "multiple-choice" situation), with genetically and phenotypically different individuals, could be another mechanism for conservation of genetic polymorphism in natural populations.     

Reproductive behaviour of the South American fruit fly Anastrepha fraterculus (Diptera: Tephritidae): laboratory and field studies

Abstract. The mate choice, courtship and oviposition behaviour of laboratory-reared and field-collected Anastrepha fraterculus (Wied.) were compared. In laboratory cultures in Southampton the duration of male calling activity in small leks increased gradually from 1-2h at 5 days old to up to 7 h at 10 days. This finding correlates with previous reports on the time at which male salivary glands, which are believed to produce sex pheromone, are fully developed. Wild flies which emerged from infested fruits in Brazil began to oviposit on the day they mated, whereas in laboratory flies oviposition began 1 day following the first mating. Both types of fly usually defended their position on a particular fruit throughout the day, and re-mated with either virgin or mated males. There was no significant difference in mating duration. Females did not copulate before the mean age (±SE) of 16.8±0.9 days. For both types of flies mating initiation occurred in the first 2h of photophase, with virgin females choosing mainly mated males. The average number of matings in the laboratory was three for females and four for males, and the interval between matings in females was significantly increased after the second mating. It is suggested that the tendency of virgin females to mate with mated males will lead to increased fitness, as males are on average 48 days old at their second mating. The potential life span of around 200 days for both sexes would allow adults to bridge the gap between seasonally available fruits in warm-temperate and sub-tropical South America.     

No evidence for minority male mating advantage in wild type strains of Drosophila ananassae tested in multiple-choice experiments

Minority male mating advantage was tested in wild type strains of Drosophila ananassae through multiple-choice experiments. Mating success of two types of flies present in five different ratios was scored by direct observation in an Elens-Wattiaux mating chamber. We found no evidence for minority male mating advantage in wild type strains of D. ananassae. The relative mating success of two types of females was also compared in the multiple-choice experiments at different ratios; there was no evidence for a rare female effect. Further, there was similarity in the results of experiments employing different methods. The total number of homogamic and heterogamic matings was obtained by combining the data (all five ratios) from each experiment. Homogamic matings were significantly more frequent than heterogamic ones, which demonstrates preferential mating between males and females of the same strain; this was also supported by a lower isolation estimate. There was also a significant difference in the degree of mating preference between the two strains.     

Patterns of sperm precedence are not affected by female mating history in Drosophila melanogaster

In promiscuously mating species, there is strong selection on males to maximize their share of paternity through both defensive and offensive means. This has been most extensively examined using the Drosophila melanogaster model system. In these studies, sperm competition has been examined by mating a virgin female to two consecutive males and then determining the fertilization success of both the first male (defending, P1) and the second male (offending, P2). Recent evidence suggests that male defense may be influenced by female mating history (i.e., virgin versus nonvirgin). Here, by mating females to males with three different genotypes, we show that female mating history does not affect male defensive or offensive abilities in sperm competition. We also show that, although female lifetime fecundity was not correlated with the number of times that she mated, it was reduced by increased exposure to males. These data indicate that measures of P1 and P2 previously reported in D. melanogaster may be robust to the specific mating history of the females used in these studies.     

Evidence for adaptive male mate choice in the fruit fly Drosophila melanogaster

Theory predicts that males will benefit when they bias their mating effort towards females of higher reproductive potential, and that this discrimination will increase as males become more resource limited. We conducted a series of experiments to test these predictions in a laboratory population of the fruitfly, Drosophila melanogaster. In this species, courtship and copulation have significant costs to males, and females vary greatly in fecundity, which is positively associated with body size. When given a simultaneous choice between small and large virgin females, males preferentially mated with larger, more fecund, females. Moreover, after males had recently mated they showed a stronger preference for larger females. These results suggest that male D. melanogaster adaptively allocate their mating effort in response to variation in female quality and provide some of the first support for the theoretical prediction that male stringency in mate choice increases as resources become more limiting.     

Influence of previous mating experience on future mating success in maleLucilia cuprina (Diptera: Calliphoridae)

Receptive and virginL. cuprina females were placed with a virgin male and an experienced male that had mated between one and five times previously. The experienced males secured significantly more matings than virgin males. Males with previous matings also gained experience in competing with males. Males directed mating attempts at each other, seemingly in the context of intrasexual competition. Experienced males directed more mating attempts at virgin males than vice versa. As their number of previous matings increased, experienced males made the first mating attempt at females more often and directed more mating attempts at females compared with virgin males. Females did not actively discriminate against experienced males, even though the proportion of matings secured on the first attempt by experienced males declined with increasing mating experience. Alternative behavioral explanations are discussed.     

Ejaculate depletion patterns evolve in response to experimental manipulation of sex ratio in Drosophila melanogaster

We assessed the extent to which traits related to ejaculate investment have evolved in lines of Drosophila melanogaster that had an evolutionary history of maintenance at biased sex ratios. Measures of ejaculate investment were made in males that had been maintained at male-biased (MB) and female-biased (FB) adult sex ratios, in which levels of sperm competition were high and low, respectively. Theory predicts that when the risk of sperm competition is high and mating opportunities are rare (as they are for males in the MB populations), males should increase investment in their few matings. We therefore predicted that males from the MB lines would (1) exhibit increased investment in their first mating opportunities and (2) deplete their ejaculates at a faster rate when mating multiply, in comparison to FB males. To investigate these predictions we measured the single mating productivity of males from three replicates each of MB and FB lines mated to five wild-type virgin females in succession. In contrast to the first prediction, there was no evidence for differences in productivity between MB and FB line males in their first matings. The second prediction was upheld: mates of MB and FB males suffered increasingly reduced productivity with successive matings, but the decline was significantly more pronounced for MB than for FB males. There was a significant reduction in the size of the accessory glands and testes of males from the MB and FB regimes after five successive matings. However, the accessory glands, but not testes, of MB males became depleted at a significantly faster rate than those of FB males. The results show that male reproductive traits evolved in response to the level of sperm competition and suggest that the ability to maintain fertility over successive matings is associated with the rate of ejaculate, and particularly accessory gland, depletion.     

Remating, sperm transfer, and sperm displacement in the cactophilic species Drosophila buzzatii Patterson & Wheeler (Diptera: Drosophilidae)

The mating system of Drosophila buzzatii is characterized by short copulation duration, frequent remating in both males and females, and male ejaculate partitioning. Additional features of the system are strong sperm displacement and a high frequency of sterile matings. Remating frequencies and the effects of remating on various mating parameters were studied. In order to characterize variation, five isofemale lines from geographically distant localities in Australia (three localities), Brazil and the Canary Islands were used. Mating parameters studied were: premating time, copulation duration, interval between successive matings, and progeny number as a measure of sperm transfer. Variation for sperm displacement was studied in crosses between laboratory stocks and a number of isofemale lines from Australia. There were significant between‐line differences in female remating frequencies, premating time, copulation duration, interval between successive matings, and progeny numbers, indicating genetic variation for these traits. Females from the five lines mated on average 1.6 to 3.1 times in 4 h, with a maximum of eight matings for one female. The males were given a maximum of ten virgin females in sequence and more than one‐third of the males mated all ten females in the 2 h observation period. Copulation duration decreased and interval between matings increased with copulation number in multiply mated males. Mean copulation duration was c. 2 min. Sperm transfer, measured as the average number of progeny from a single mating, was low (c. 25) and multiply mated females gave more progeny than single mated females, although with much lower progeny numbers than observed in wild‐caught non‐virgin females. A surprisingly high proportion of observed matings gave no progeny, i.e. they were sterile matings. Sperm displacement was strong in most crosses and remained strong in multiply mated females. The results are discussed in relation to the evolution of mating patterns in Drosophila.     

The cost of mating rises nonlinearly with copulation frequency in a laboratory population of Drosophila melanogaster

Previous studies of Drosophila melanogaster have demonstrated a cost to females from male courtship and mating, but two critically important parameters remain unresolved: (i) the degree to which harm from multiple-mating reduces lifetime fitness and (ii) how harm from mating might change with successive matings (rematings). Here we use 'laboratory island analysis' to quantify the costs that females incur with each remating, in the currency of lifetime fitness and under conditions that closely match those to which the flies have adapted for hundreds of generations. We experimentally manipulated the number of female matings by varying the order of daily 2-h exposures of females to either sperm-less males (XO) or intact males (XY). Females that mated more often had substantially reduced lifetime fecundity, and importantly, the fitness cost from remating rapidly accelerated.     

Multiple mating in wild Drosophila melanogaster revisited by microsatellite analysis

The occurrence of multiple mating in Drosophila melanogaster is of particular interest to evolutionary biologists, as seminal fluid has some toxic effects for females. Thus, it has been predicted that the number of matings per females should be low. We have tested this prediction with seven highly polymorphic microsatellite loci in inseminated females from a Viennese D. melanogaster population. In contrast to the predicted low number of matings and previous studies in natural populations, we identified the genotypes of four to six different males fertilizing the offspring of each female tested. Potential causes and consequences are discussed.     

INTERACTIONS BETWEEN ENVIRONMENTAL STRESS AND MALE MATING SUCCESS MAY ENHANCE EVOLUTIONARY DIVERGENCE OF STRESS-RESISTANT DROSOPHILA POPULATIONS

Adaptation of natural and laboratory-selected populations of Drosophila to desiccation stress results in enhanced water conservation abilities, and thus increased stress resistance. In this study, we tested whether laboratory selection for desiccation resistance is also reflected in increased mating success of adapted D. melanogaster males under desiccating conditions. Adapted flies perform better under stressful conditions, and as expected males from desiccation-selected populations exhibited significantly higher relative mating success in comparison with controls after 5–6 h of desiccation. However, we show evidence for a trade-off between survival under stressful conditions and mating success in nonstressful and even mildly stressful environments (2.5–3 h of desiccation), where males from selected populations were involved in only ∼40% of observed copulations. This suggests that mutations favored by natural selection, associated with survival when resources are limited, may only be favored by sexual selection above a minimal "threshold" stress level. At milder stress levels increased resistance comes at a cost of lower relative mating success, and thus reduced fitness. This interaction between stress and relative male mating success of adapted and nonadapted males could interrupt gene flow, thus facilitating divergence of resistant populations from the ancestral population.     

Evolution of a desaturase involved in female pheromonal cuticular hydrocarbon biosynthesis and courtship behavior in Drosophila

Drosophila species exhibit polymorphism in female pheromonal cuticular hydrocarbons, with 7-monoenes produced in Drosophila simulans and 7,11-dienes in most populations of Drosophila melanogaster (5,9-dienes in several African populations). A female-biased desaturase, desatF, expressed only in D. melanogaster is involved in the synthesis of 7,11-dienes. We investigated the role of desatF in 5,9-diene flies. We constructed a 5,9-diene strain knock-down for desatF and showed that desatF is involved in 5,9-diene formation. We also studied D. melanogaster/D. simulans hybrids. These hybrid females produced dienes and received normal courtship from D. melanogaster males, but copulation success was reduced. With D. simulans males, courtship was decreased and no copulation occurred. Hybrids with a chromosomal deletion of the D. melanogaster desatF gene had no dienes and received normal courtship from D. simulans males; depending on the D. simulans parental strain, 7-19% of them succeeded in mating. D. simulans desatF promoter region shows 21-23% gaps and 86-89% identity with D. melanogaster promoter region, the coding region 93-94% identity, depending on the strain. These differences could explain the functional polymorphism of desatF observed between both species, contributing to different cuticular hydrocarbon profiles, that constitute an effective barrier between species.     

Cost of reproduction in male medflies: The primacy of sexual courting in extreme longevity reduction

In polygynous insect species, male reproductive success is directly related to lifetime mating success. However, the costs for males of sexual activities such as courting, signaling, and mating are largely unknown. We studied the cost of sexual activities in male Mediterranean fruit flies, Ceratitis capitata (Tephritidae), a polygynous lekking species, by keeping cohorts of individual male flies under relaxed crowding conditions in the laboratory. We used 5 cohorts among which individuals differed in their opportunities to interact with con-specifics and recorded life span, and in one treatment, mating rate. We found that males kept singly lived more than twice as long as males that interacted intensively with mature virgin females, while male-male interactions caused a smaller reduction in longevity. Because longevity of males that could court but not mate was not significantly different from those that could court and mate, we conclude that courting (not mating) was responsible for the observed longevity reduction. Moreover, we detected high variability in male mating success, when 5 virgin females were offered daily. In contrast to the cohort level, individual males that mated at a high rate lived relatively long, thus indicating heterogeneity in quality or sexual strategy among males.     

Mating and hormonal triggers regulate accessory gland gene expression in male Drosophila

Drosophila melanogaster males transfer accessory gland proteins, as part of their seminal fluid, to females during each mating. Since accessory gland proteins are important for male reproductive success, it is important that the male replenish the proteins he transferred during mating. Previous studies had shown that mating induces the resynthesis of accessory gland proteins, but since mating includes a set of stereotyped behavior patterns as well as the act of copulation, it was not known which aspect of the mating process induces accessory gland protein synthesis. By exposing males to females whose ovipositors had been sealed shut, we have shown that resynthesis of accessory gland proteins occurs only when seminal fluid is transferred to females. By applying juvenile hormone or 20-hydroxyecdysone topically to the cuticle of male flies, we showed that these hormones can act in vivo to stimulate the synthesis of accessory gland proteins to levels similar to those observed after mating.     

Accessory gland secretory proteins in relation to fitness parameters of Drosophila ananassae and D. varians

Developmental morphometry, qualitative and quantitative analysis of the accessory gland secretory proteins, fecundity and productivity in relation to protein ejected during subsequent (first to fourth-time) matings have been studied in Drosophila ananassae Doleschall and Drosophila varians Bock. In both species, size and secretion of accessory glands increases from 1 to 8 days and the stored secretion ejected from males to the female genital tract during subsequent mating varies. The maximum number of eggs and flies are produced from the females mated with bachelor males and it is a minimum when virgin females are mated with fourth-time mated males. Sodium dodecylsulfate–polyacrylamide gel electrophoresis analysis of accessory gland secretory protein patterns and their glycosylation differs in both the species. Correlation coefficient analysis between gland size and quantity of secretion, percentage of secretory protein transferred per mating, and eggs and flies that emerged showed a highly significant, positive relationship. Among different matings, the number of eggs laid and flies that emerged per female between subsequent (first to fourth-time) matings of males was found to be highly significant and the difference between fecundity and productivity between the two species was highly significant.     

Sex peptide causes mating costs in female Drosophila melanogaster

Conflicts between females and males over reproductive decisions are common . In Drosophila, as in many other organisms, there is often a conflict over how often to mate. The mating frequency that maximizes male reproductive success is higher than that which maximizes female reproductive success . In addition, frequent mating reduces female lifespan and reproductive success , a cost that is mediated by male ejaculate accessory gland proteins (Acps) . We demonstrate here that a single Acp, the sex peptide (SP or Acp70A), which decreases female receptivity and stimulates egg production in the first matings of virgin females , is a major contributor to Acp-mediated mating costs in females. Females continuously exposed to SP-deficient males (which produce no detectable SP ) had significantly higher fitness and higher lifetime reproductive success than control females. Hence, rather than benefiting both sexes, receipt of SP decreases female fitness, making SP the first identified gene that is likely to play a central role in sexual conflict.     

MALE EFFECTS ON FECUNDITY IN DROSOPHILA MELANOGASTER

Effects of male Drosophila melanogaster on female fecundity and productivity were examined, considering both females held in containers with males and females exposed to male effects not involving contact. Females were more fecund when male effects were present, and the largest increase was recorded when vials were previously conditioned by males. This effect was probably due to the growth of transmitted microorganisms, which were observed on the laying surface, as further experiments with vials conditioned by virgin females showed a similar increase in fecundity. A male-specific effect was isolated by conditioning bottles containing only agar with males and virgin females. The observation of a male factor that stimulates oviposition without mating is novel and suggests complicated fertility interactions between the sexes.     

Mate choice in Drosophila melanogaster and D. sechellia: criteria and their variation depending on courtship song

Courtship song is one of the most important male signals in Drosophila mating. A female D. melanogaster copulates more readily when given a conspecific type of courtship song. Female D. melanogaster accepted winged D. sechellia more than wingless ones in a no choice test. Copulation frequencies varied between strains and were significantly correlated with male mating propensity of D. sechellia. Females from three of five strains of D. sechellia accepted winged D. melanogaster less than wingless ones in no choice tests, suggesting that D. melanogaster songs reduce mating in D. sechellia females. Multiple choice tests showed that males prefer conspecifics. In female choice tests, D. melanogaster females copulated with winged heterospecific D. sechellia males more than with wingless conspecific D. melanogaster males in the confined condition, suggesting that song differences between D. melanogaster and D. sechellia affect D. melanogaster females less than the absence of courtship song. Copyright 2000 The Association for the Study of Animal Behaviour.     

Multiple mating and repeated copulations: effects on male reproductive success in red flour beetles

In many insects, both sexes mate multiple times and females use stored sperm for fertilizations. While males frequently engage in two distinct behaviours, multiple mating (with different females) and repeated copulations (with the same female), the reproductive consequences of these behaviours for males have been quantified for only a few species. In this study, males of the red flour beetle, Tribolium castaneum, were found to be capable of mating with as many as seven different virgin females within 15 min. Across sequential copulations with virgin females, there was no decline in either male insemination success or average female progeny production over 48 h. However, when males copulated with previously mated females, there was a significant decline in male paternity success across sequential copulations, possibly due to male sperm depletion. In separate experiments, T. castaneum males were found to engage in two to six repeated copulations with the same, individually marked female. These repeated copulations did not increase male insemination success, short-term female fecundity, or male paternity success. Repeated copulations may possibly play a role in sperm defence. This study indicates that males may frequently engage in multiple matings, but these additional matings may lead to diminishing male reproductive returns.