Swarm Site Fidelity in the Sex Role-Reversed Dance Fly Empis borealis

In the dance fly species Empis borealis (L.), females (1–40) gather to swarm at landmarks (swarm markers, like trees and bushes), and males carrying an insect prey visit these swarms for mating. We noticed earlier that some swarm sites were used for several years and that they appeared to be frequented by a similar number of swarming females in each year, although the numbers of females varied greatly among swarm sites and certain sites attracted more swarming individuals than others. To explore swarm site fidelity in this mating system, in 1993 we monitored the same swarm sites that we studied in 1989, addressing the questions, Would the same swarm sites still attract the same number of females and males after 4 years? and Why do some swarm sites attract more displaying females than others? The number of females swarming at the different markers in 1993 was approximately the same as 4 years earlier. Some of these swarm sites are known to have been used for 18 years. The swarm sites with the largest number of flies had a high sun exposure during the day and were found at coniferous swarm marker trees and in a mixed forest habitat. A swarm site with few females attending and with a low amount of insolation during the day can be predicted to be abandoned as a swarming site soon. Empis borealis swarm sites thus persist over many years and are attended by a similar number of individuals each year. To our knowledge, such site fidelity has not been demonstrated for any swarming insect species earlier.     

Nuptial gift size prolongs copulation duration in the dance fly Empis borealis

Abstract. 1. The time that pairs of the dance fly Empis borealis (L.) (Diptera: Empididae) spent in copula was positively correlated with the volume of the nuptial gift.
2. In some cases the copulation duration was short although prey volume was large. Females engaged in these matings had more worn wings, were therefore older, and most probably had sperm already stored in the spermatheca. It is suggested that these copulations were interrupted because either the spermatheca was full of sperm and the male was not able to transmit any sperm, or because prey content was depleted (males may have fed on the prey or the prey had been used in a previous mating). The latter explanation seemed more probable.
3. A male providing a large nuptial gift may transfer larger quantities of sperm. Quantitative sperm competition is more likely than last-male sperm predominance.     

Male Dominance Rank,Female Mate Choice and Male Mating and Reproductive Success in Captive Chimpanzees

Mating and consequently reproductive success in male vertebrates are predominantly determined by intermale competition and female mate choice. Their relative importance however, is still poorly understood. We investigated the interrelationship between male dominance rank — a formal indicator of male competitive ability — female mate choice, and male mating success in a multimale-multifemale group of captive chimpanzees. In addition, we examined the relationship between male dominance rank and reproductive success determined by genetic paternity analysis over a 13-yr period in the same captive population. We related the frequencies of sociosexual behaviors to the female anogenital swelling stage and female fertile phase as determined by urinary and fecal progestogen analysis. Rates of behaviors in both sexes increased with increasing intensity of female swelling, but they were not influenced by the timing of the fertile phase. Male mating success was clearly related to male dominance rank, with high-ranking males performing the overwhelming majority of copulations. This was mainly due to both rank-related rates of male soliciting behavior and intermale aggressiveness during the period of well-developed female anogenital swelling. Although females solicited copulations mainly from the high-ranking males and thus expressed a mate choice based on rank, their overall contribution in initiating copulations and thus influencing male mating success was low. The data on paternity from the population, which always contained 4 adult males, revealed that -males sired the majority (65%) of offspring. We conclude, that male dominance rank is an important determinant of male mating and reproductive success in captive (and presumably wild) chimpanzees and that female mate choice is of minor importance in modulating male reproductive outcome.     

Male Age and Experience Increases Mating Success but Not Female Fitness in the Mexican Fruit Fly

Male age and sexual experience are important condition parameters that can influence mate choice and female fitness, yet they are seldom studied simultaneously. Here, we investigated the effect of male age and previous sexual experience on mating success and female fitness in the Mexican fruit fly, Anastrepha ludens (Diptera: Tephritidae). Males were either young or old, sexually experienced or naïve. Older and sexually experienced males obtained more copulations. However, females did not receive benefits in terms of lifetime fecundity, fertility, or longevity from mating with these males. Results suggest that males become more competitive as they age and gain sexual experience and may be able to maintain a high quality ejaculate compared to young males. Older experienced males may be manipulating females into preferentially mating with them at no benefit to females. Alternatively, females may prefer mating with older more experienced males and possibly receive other indirect benefits, but this remains to be tested.     

Male Mating History Influences Female Mate Choice in the Trinidadian Guppy (Poecilia reticulata)

Based on the phenotype‐linked fertility hypothesis, sexual selection should favour females that can accurately assess the recent mating history of available sexual partners and preferentially avoid mating with recently‐mated males [who may be sperm depleted (SD)] so as to minimize the risk of their eggs not being fertilized. This hypothesis has received to date only limited attention and empirical support. Therefore, in the current study, we investigated experimentally whether females of a vertebrate species, the Trinidadian guppy (Poecilia reticulata), are able to assess the recent mating history of males, and thus potentially their functional fertility, and choose to avoid mating with males that appear to have recently mated and who may be sperm limited. Individual virgin females were first given a dichotomous choice between a male that had not been recently observed to interact sexually with another female (i.e. not sperm‐depleted) and another male that had been observed to interact sexually with a female (i.e. potentially sperm‐depleted) as sexual partners. Paired males were matched for body length and coloration. Immediately following this test, the focal females were subjected to a free‐swimming mate‐choice test using the same paired stimulus males. As predicted, on average, female guppies avoided the apparently recently‐mated (and potentially sperm‐depleted) male and exhibited a significant preference for the other male not recently observed mating (and thus not likely sperm limited) during both tests. We do not yet fully understand the underlying mechanisms of this preference. Therefore, further research on the particular cues that females use to assess the recent mating history and fertility status of males is required.     

Mating Effort and Cryptic Sperm Choice in Scorpionflies: Male Investment Strategy vs. Female Control

In this study, we examined which sex controls sperm transfer during copulation in scorpionflies. Therefore male scorpionflies were doubly mated to females of high and low fecundity to explore whether they allocate sperm according to female quality. While mating order had no effect males transferred sperm at higher rates when mating with low‐quality instead of high‐quality females. As there is no obvious benefit from providing low‐fecundity females with more sperm, we suggest a condition‐dependent female ability to counteract sperm transfer. Therefore, we disabled females at the beginning of copulations using the insecticide Propoxur which leads to total paralysis caused by tremors. While the provoked muscle contractions led to significantly smaller numbers of sperm transferred, Propoxur treatment had no effect on males. We suggest female counteracting of sperm transfer to be adaptive by decreasing the relative amount of sperm transferred by low‐quality males and increasing the proportion of offspring sired by high‐quality males.     

Lek Mating System and Large Male Aggressive Advantage in a Gall-forming Tephritid Fly (Diptera: Tephritidae)

Field and laboratory studies revealed that the mating system of a tephritid fly, Procecidochares sp., meets even the most stringent definition of lekking behavior. Mark-recapture and plant-preference experiments confirmed that newly emerged adult Procecidochares sp. left their larval host plant (Chrysothamnus nauseosus) and flew to Atriplex canescens. The flies used A. canescens solely as a mate encounter site. Sex ratios of emerging flies did not differ from unity, but sex ratios at the leks were extremely male-biased. An advantage for larger individuals in male-male aggressive encounters was quantified and observations suggested that females might be choosing mates based on outcomes of fights. Lekking behavior, previously reported among polyphagic tephritids, is considered exceptional for a monophagous species. Factors favoring a lek mating system in this species are discussed.     

Mating Status and Choice of Group Size in the Phoretic Fly Norrbomia frigipennis (Spuler) (Diptera: Sphaeroceridae)

The phoretic sphaerocerid fly Norrbomia frigipennis mates on scarabid dung beetles, follows them underground, and lays eggs in the collected dung. We found that male and female flies distribute themselves nonrandomly on beetles with respect to fly group size. The proportion of virgin females increased with group size, and females with mature eggs were most frequently found on beetles carrying fewer flies. Laboratory experiments revealed that mated females avoided larger groups, virgin females seemed to prefer large groups and mated females, small groups. Males showed no such pattern. These results suggest that N. frigipennis can estimate group size, presumably an adaptation with a reproductive function. However, flies did not join hosts on the basis of the sex of already mounted flies.     

The High Price of Success: Costs of Mating Effort in Male Primates

While males are generally the low investing sex when it comes to offspring care, males of many species experience intense and persistent mating effort. Mating effort incurs a variety of costs which are expected to have non-negligible effects on fitness, as well as how reproductive tactics are selected and investment in mating activity is moderated over time. This special issue features contributions investigating the costs of male mating effort across primate species. Here, we place these exciting new works in context, addressing the specific types of mating effort expected for male primates and the significance of these costs for our understanding of primate life histories and socioecology.     

Male Competition,Mating Success and Female Choice in a Seasonally Breeding Primate (Erythrocebus patas)

Mammals with restricted breeding seasons often show brief but intense bouts of male competition for mates and male reproductive success has been attributed to male competitive abilities, with the most aggressively successful males able to control access to fertile females, or with females choosing to mate with such males. We studied male competition, mating behaviour and female mate selection in patas monkeys, a primate with a restricted breeding period. We observed two habituated patas groups in Laikipia District, Kenya, during Jun.-Aug. 1983. During the study, one group had a single resident male while the other group had multiple adult males. Within the multimale group, experienced adult males were no more successful than the subadult male. The sole resident male had a significantly higher rate of fights won (p < 0.02) although he did not differ from the multimale group males in rate of aggression or initiation of fights. We found no significant differences in either mating success or female preference based on males' experience or residency. The rates at which males copulated with and were solicited by females were not significantly correlated. We found no evidence of stable dominance ranks among males in the multimale group and aggressive success was not significantly correlated with copulation rate for males in the multimale group. Subadult males were responsible for the majority of copulations observed during the final third of the breeding season. Our observations of this patas population showed a fluid number of males in groups, with the same groups able to shift rapidly from single to multimale structure. This fluidity may result from the large fluctuations in numbers of breeding-age males and females observed over 4 yr of studying this population.     

The Mating Strategy of the Male Short-tailed Cricket Anurogryllus muticus de Geer

Males of Anurogryllus muticus de Geer call with a sound intensity of 92–95 dB SPL/20 cm. The nightly calling time is 198 ± 79.5 min. Singing begins with the onset of darkness, and is under circadian control (τ_LL = 25.35 h). At 27 ° C, O₂-consumption during rest is 1.7 ml/h/g, whereas for calling O₂-consumption rises to 10.76 ml/h/g. According to the CO₂/O₂ ratio, A. muticus burns carbohydrates and lipids at rest, but mostly lipids during stridulation (R = 0.8). The type of fuel oxidized is rapidly adjusted to the particular behavior expressed. The testes serve as a reservoir for lipids, and their lipid level rises from 33.2 ± 15.4 μg/mg tissue at the imaginal molt to 95.2 ± 43.1 μg/mg tissue by the age of 30 days, although by that time testis size has shrunk by 90 %. Multiple, brief matings compensate for short calling times due to high energy expenditure. Comparative data for Teleogryllus oceanicus and T. commodus are given, where appropriate.     

The Energetics of Male Mating Strategies in Field Crickets (Orthoptera: Gryllinae: Gryllidae)

Male field crickets (Gryllinae: Gryllidae: Orthoptera) vary in their mating strategies, particularly in whether they call from defended sites to attract phonotactic females or roam silently in search of potential mates. To better understand the economics underlying these alternative strategies, respirometry was employed to examine the energetic costs of each strategy's component behaviors for a representative species, Acheta domesticus. Advertisement calling in this species, composed of low pulse rate chirps, is an order of magnitude less energetically costly than walking per unit time. However, for gryllids that advertise call with higher pulse rate trills, calling and walking appear to be of equivalent energetic cost. Thus, if energetic costs are important in determining grylline mating strategies, trillers and chirpers should have different sensitivities to change in factors affecting the relative payoffs of each strategy. Field studies of changes in mating behavior with increased population density support this argument. This study also determined that courtship calling by A. domesticus was over twice as energetically costly as advertisement calling per unit time, suggesting its importance as a more reliable indicator of signaler, or mate, quality.     

The Payoff of Fighting in House Crickets: Motivational Asymmetry Increases Male Aggression and Mating Success

Motivational asymmetry caused by differences in subjective resource value is a key component of strategic models of aggression. We study the role of motivational asymmetry in determining differential aggression and mating success of male house crickets, Acheta domesticus. We also assess the extent to which mating differences associated with motivational asymmetry are due to direct male–male fighting vs. male–female interactions. We manipulated male motivation to compete for a mating opportunity by providing males with either no access or nightly access to females for 4 d prior to the experiment. As predicted, when males from each treatment had to compete for the female, those with lower prior access were more aggressive and mated more often. In contrast, when males from each treatment were paired individually with females, there was no significant difference in the frequencies with which they pursued, courted or mated with females. We also found no evidence for female choice based on motivational asymmetry; the rate of successful courtship did not differ between treatments. We conclude that prior mate encounter rate can generate motivational asymmetry, leading to differential mating success mediated by direct male–male aggression.     

Size-Dependent Mating Success at Various Nutritional States in the Yellow Dung Fly

Mating success not only depends on genetic quality, but also equally on environmental factors, most prominently food availability. We investigated the interactive effects of nutritional state and body size on mating success and copula duration in yellow dung fly males ( Scathophaga stercoraria ; Diptera: Scathophagidae) of three body size selection lines in the laboratory in both non-competitive (single) and competitive (group) situations. Adults require protein and lipids from prey to reproduce, as well as sugars as an energy source for reproductive activity. We expected mating success to decrease with time because of sperm depletion (sugar treatment) and/or energy shortage (water treatment) relative to the control, prey plus sugar treatment. Based on physiological scaling, we also expected large-line males to become depleted either sooner because of their higher energy and sperm demands, or later because of their more efficient energy use. Average mating success indeed declined over a period of 5–7 d (or 5–15 potential copulations per male), but equally for all food treatments and body size classes. Surprisingly, water-fed and small-line males had the highest mating probability in the non-competitive setting, while in the competitive setting large-line males had the highest success. Energy-depleted males showed apparent terminal investment. Small males acquired females more readily but eventually lost them to larger males in the competitive situation. As shown before, copula duration was inversely related to body size and increased with copulation number, independent of food treatment. We conclude that sugar or prey shortage has little effect on mating success in the short term, and does not differentially affect males of different sizes.     

The Haremic Mating System and Mate Choice in the Wide-Eyed Flounder, Bothus podas

The social structure and reproductive behaviour of the wide-eyed flounder, Bothus podas, was studied in the coastal waters around the Azorean Islands. Both sexes are territorial throughout the year. Adult males defend large territories, which include several smaller female territories. Intraspecific agonistic behaviour was frequent and differed between sexes: males were more aggressive towards other males, while females were only aggressive towards each other and juveniles. During the reproductive season and only at dawn, territorial males court and mate successively with females in their territories, and females seem to show mating fidelity to their dominant male. Such territoriality and mating patterns indicate a haremic social system in the wide-eyed flounder. In order to identify potential factors influencing female mate choice acting on this haremic system, we examined male mating success and some of its potential correlates. We found no evidence for female preference for any of the males' physical or territory characteristics. However, courtship effort was strongly correlated with the total number of attempted and successful spawnings, indicating that females seem to mate preferentially with males that court them more vigorously. Thus, our data suggest that courtship plays an important role in determining male mating success in the wide-eyed flounder and, that it may possibly serve as an honest indicator of male `quality' for female choice.     

Male Courtship Song Frequency as an Indicator of Male Mating Success in Drosophila montana

Drosophila montana females have been found to prefer overwintered males with short and dense (high-frequency) sound pulses in the wild. In the present study males producing high-frequency song succeeded in their courtship more often than males producing low-frequency song in mate-choice experiments. Male mating success correlated with the carrier frequency of the male song recorded after, but not before, an artificial winter (flies kept 6 months at 4°C). The finding that female preference is based on a male song trait changing considerably during overwintering suggests that this trait may reflect the viability and condition of the males during the mating season of the flies in spring.     

Mating Group Size and Stability in Reindeer Rangifer tarandus: The Effects of Male Characteristics,Sex Ratio and Male Age Structure

In polygynous mating systems, males compete intensely for mates and may mate several females during a single reproductive season. Accordingly, factors influencing the ability of males to control a larger number of females during the breeding season can provide information on the processes underlying sexual selection. In ungulates, age, body mass and social rank are considered good predictors of the reproductive success of males, but how male age structure and sex ratio in the population influence mating group (MG) dynamics has received little empirical testing. Between 1996 and 2005, we manipulated male age‐ and sex structure and monitored MG dynamics in a reindeer (Rangifer tarandus) population. We investigated the influence of male characteristics, percentage of males and male age structure on MG size and stability. We found that males with higher social rank (that were also older and heavier) controlled larger MGs (therefore had greater mating opportunities) and had more stable MGs (corresponding to a higher ability to maintain and control females) than males of lower social rank. Moreover, MG size and MG stability decreased as the percentage of males in the population increased, most likely resulting from greater male–male competition and increased female movements. Male age structure did not influence MG stability. Given the positive relationship between mating success and MG size (and likely MG stability), frequent female movements and intense competition among males to control females seem to be the principal components of reindeer MGs dynamic.     

Male Condition, Female Choice, and Extreme Variation in Repeated Mating in a Scaly Cricket, Ornebius aperta (Orthoptera: Gryllidae: Mogoplistinae)

Mating in the scaly cricket Ornebius aperta often includes the transfer of many spermatophores to individual females during extended copulatory interactions. We manipulated male condition in staged matings to determine whether this could explain variation in the number of repeated copulations seen across pairs. Males on a high nutrient diet were in good condition, were more likely to mate repeatedly, and transferred more spermatophores on average than low-diet males (in poor condition). High-diet males were more likely to produce a vibratory signal that increased female receptivity to repeated mating attempts. Courtship and copulatory interactions were always terminated by females, and in every case males had already formed a spermatophore when deserted by females. We conclude that variation in male repeated mating success may be due to female choice rather than an inability or unwillingness of low-diet males to produce spermatophores.     

The Mechanistic Basis of a Large Male Mating Advantage in Two Freshwater Amphipod Species

In many animals, body size plays an important role in determining both ecological success and mating success. Thus, the expression of body size within a population is often the result of the interaction between natural selection and sexual selection. Here, I examine the mechanistic basis for a large male mating advantage in two freshwater amphipod species that differ ecologically. Traditionally, size‐biased mating patterns in amphipods have been attributed to the advantage of large size in male–male competition for females. In this study, when direct male–male interactions were eliminated (via tethering), large males had a mating advantage similar to that observed under control conditions (males free to interact) and in previous field and laboratory studies. These results suggest that male–female interactions play an important role in selecting for large male size. There was, however, some evidence for male takeovers in the species that shows the stronger size‐based mating bias. Takeovers occurred in 33% of trials when smaller males were in the position of defender, i.e. paired with the female. Therefore, takeovers by larger males may also contribute to the strong size‐based mating biases observed in this species.