Alternative mating tactics in male white-faced dragonflies (Leucorrhinia intacta): plasticity of tactical options and consequences for reproductive success

Summary Alternative tactics used by males to obtain mates usually are associated with genetic and/or phenotypic differences between the behavioral morphs. This system of white-faced dragonfly (Leucorrhinia intacta) alternatives is characterized by plasticity of tactical options for individual males. Males may act either as territorials, and defend small perch-centered territories on the study pond, or they act as transients, spending most of their time in vegetation surrounding the pond and sallying out at intervals in search of mates. The two tactics remain in constant proportions over a broad range of densities, so transients do not result only from a filling in of suitable territorial sites. Males adopt tactics independently from day to day, with no significant influences of phenotypic variation, priority of arrival at the breeding site, or prior success in a role. We interpret this system as based on conditional, frequency-dependent choice of alternatives by a population of males not differing significantly in their abilities to employ one tactic or the other, but we cannot exclude entirely the possibility of mixed strategies. Average daily mating success is equal for territorial and transient males, supporting predictions of mixed and conditional ESS hypotheses. Males of each tactic obtain matings daily in proportion to their representation in the population for most data samples. Deviations from the expected mating success provide no information of use in selecting one or the other tactic on subsequent days. We suggest this system of alternatives represents a conditional mating strategy, in which males adopt tactics based on the availability of perches relative to oviposition substrate and on interactions within and between tactics that are influenced by the relative frequencies of territorial and transient males.     

The contribution of multiple mating and spermatophore consumption to the lifetime reproductive success of female field crickets (Gryllus bimaculatus)

ABSTRACT.

• 1 The adaptive significance of multiple mating by female Gryllus bimaculatus (De Geer) was investigated.
• 2 Multiple mating prevented the depletion of sperm stores and, therefore, maintained high hatching success. This may not, however, explain the high frequency of remating in this species.
• 3 Male-derived egg stimulants known to be passed with sperm at mating increased the number of eggs produced only when females mated throughout their lifespans.
• 4 Spermatophore consumption appeared to provide nutrients which, while they did not increase the quantity of eggs, increased egg quality as indicated by weight. Females who consumed spermatophores had a greater hatching success.
• 5 While females may derive non-genetic benefits from mating, these are apparently long-term benefits; females must mate throughout their lives in order to accrue them.
• 6 Since the benefits of mating may not be derived from individual males, the spermatophores and their contents in this species are best considered as mating effort.

     

Observations on the mating behavior of the alfalfa blotch leafminer,Agromyza frontella (Rondani) (Diptera: Agromyzidae), and evidence of a female sex pheromone

The mating behavior of Agromyza frontella was studied under laboratory conditions. Adults were able to mate on the day of emergence, with no evident periodicity throughout the photophase. The host plant was essential for mating to occur, its presence affecting female receptivity rather than male copulatory behavior. Males generally entered a stationary phase once in the proximity of a female, before undertaking a final approach. This stationary behavior frequently resulted in male aggregations around a female, and under such conditions males exhibited a characteristic wing vibrating behavior. As male wing vibration was not an essential behavior for successful mating, and rarely occurred during male encounters in the absence of females or when only one male was near a female, it was considered as being primarily a male-male signal. The majority of females that mated exhibited an ovipositor pumping behavior that stimulated the male approach. However, such behavior was not essential to attract mates, as dead females elicited the entire sequence of male mating behavior. This suggested the presence of a cuticular sex pheromone, as reported for other species of higher Diptera. Whole virgin female (<24- h or 3- day-old) hexane extracts applied to male cadavers increased the time males spent on the plant, the number of contacts with the treated cadavers, the incidence of attempted copulations, and the wing vibrating behavior between males compared with controls using untreated cadavers. The results obtained indicate that females control copulation in A. frontella and that both semiochemical and visual cues are important in eliciting male mating behavior.     

Repeatability: Its role in evolutionary studies of mating behavior

Summary Repeatability, a concept derived from quantitative genetics theory, is a statistic that describes the degree to which variation within individuals contributes to total variation in a population. Its usual application has been to set an upper limit on heritability but it may also be useful for studies of stereotypy of behavior. The repeatability of the production of male mating signals gives information both about whether males differ sufficiently for selection to act and whether the differences could be appreciably heritable. Measures of the repeatability of female mating preferences will provide data that can describe the preference functions used in mathematical models of the evolution of sexually selected traits, as well as putting an upper bound on the heritability of preferences. A survey of the few measures in the literature shows that the repeatability of male signal production varies substantially (range 0.21–0.85) and does not necessarily reflect heritability. The repeatabilities of female preferences have not been published previously: for the response to conspecific pheromones by female flour beetles (Tribolium castaneum), my best estimate is zero. Measuring the repeatability of other traits such as parental care and foraging behavior may also lead to insights about selection on and the evolution of these traits.     

A double role of sperm in scorpions: The mating plug of Euscorpius italicus (Scorpiones: Euscorpiidae) consists of sperm

Mating plugs occluding the female gonopore after mating are a widespread phenomenon. In scorpions, two main types of mating plugs are found: sclerotized mating plugs being parts of the spermatophore that break off during mating, and gel‐like mating plugs being gelatinous fluids that harden in the female genital tract. In this study, the gel‐like mating plug of Euscorpius italicus was investigated with respect to its composition, fine structure, and changes over time. Sperm forms the major component of the mating plug, a phenomenon previously unknown in arachnids. Three parts of the mating plug can be distinguished. The part facing the outside of the female (outer part) contains sperm packages containing inactive spermatozoa. In this state, sperm is transferred. In the median part, the sperm packages get uncoiled to single spermatozoa. In the inner part, free sperm is embedded in a large amount of secretions. Fresh mating plugs are soft gelatinous, later they harden from outside toward inside. This process is completed after 3‐5 days. Sperm from artificially triggered spermatophores could be activated by immersion in insect Ringer's solution indicating that the fluid condition in the females' genital tract or females' secretions causes sperm activation. Because of the male origin of the mating plug, it has likely evolved under sperm competition or sexual conflict. As females refused to remate irrespective of the presence or absence of a mating plug, females may have changed their mating behavior in the course of evolution from polyandry to monandry. J. Morphol., 2010. © 2010 Wiley‐Liss, Inc.     

Swarming, Delayed Sexual Maturation of Males, and Mating Behavior of Fopius arisanus (Sonan) (Hymenoptera: Braconidae)

Fopius arisanus is unusual among hymenopterous parasitoids in males having an obligatory premating period. We confirmed Hagen's (1953) view that sperm takes several days to migrate from the testes to the seminal vesicles. Males mated for the first time only 4 days after emergence, the time that sperm was first ever recorded in the seminal vesicles. In the field, we studied the sexual maturation of F. arisanus males in relation to their behavior. In general, sexually immature males were found in male-only swarms that persisted over several days in host tree canopies. Mature males were usually found in loose aggregations in the vegetation beneath host trees. Females entered these loose aggregations and were mated, whereas they were generally absent from swarms in the canopy. Swarming is therefore apparently not a primary component of the sexual communication system of the species. We describe, for the first time in F. arisanus, the behavioral sequence that accompanies the intersexual communication that leads to mating. Males probably release a volatile chemical that attracts females from a distance, but we have only circumstantial evidence for this. We also postulate that males may form aggregations to amplify the effects of this distance attractant. In the vicinity of males, females release a pheromone that attracts males, a process we demonstrated with female-baited sticky traps.     

Processes underlying complex patterns of song trait evolution in a Setophaga hybrid zone

During secondary contact between two species when hybrids are less fit than parents, mating signals are expected to diverge, while aggressive signals are expected to converge. If a single signal trait is used in both mating and aggression, then the dynamics between these two forces could influence the evolutionary trajectory of that trait. We studied such a situation in an avian hybrid zone between two Setophaga species, where birdsong is used in both mate attraction and territory defense. We hypothesized that song modules of the two species will show separate and distinct geographic patterns due to the influence of selective pressures for effective territorial aggression and for effective mate attraction. We conducted geographic cline analyses and playback experiments across this hybrid zone. We found an unexpected geographic pattern of asymmetric introgression of song rhythm, which may be explained by results of the playback experiments that suggest that differences in song rhythm serve a greater role in mate attraction than in territory defense. In contrast, differences in syllable morphology show little evidence of importance in mate attraction or territorial defense. Song features converge in the hybrid zone, yet patterns of trait change suggest that the song production modules may vary in their modes of development and inheritance. Syringeal motor gesturing, which gives rise to syllable morphology, shows a nonclinal mosaic pattern, suggesting that this trait may be predominantly learned. In contrast, respiratory patterning, which forms song rhythm, shows a clinal geographic transition, suggesting that this trait could be more innate. The results indicate that opposing forces act independently on song via distinct modules of the song production mechanism, driving complex patterns of song trait evolution.     

Reproductive success in a natural population of male three‐spined stickleback Gasterosteus aculeatus: effects of nuptial colour,parasites and body size

The effects of nuptial colour, parasites and body size on reproductive success were examined in a natural population of three‐spined stickleback Gasterosteus aculeatus. Reproductive males were collected, with the contents of their nests, during the embryo‐guarding stage from Lynne Lake (Cook Inlet, Alaska, U.S.A.), and nuptial colour, infection status and body size were recorded. Regression analysis revealed that male body size was the only predictor, of those measured, of reproductive success in nature.