Sexual Interference Research Articles

Adaptive significance of flexistyly in Alpinia blepharocalyx (Zingiberaceae): a hand-pollination experiment.

Flexistyly is a sexual dimorphism where there are two morphs that differ in the temporal expression of sexual function and also involve reciprocal movement of the stigmatic surface through a vertical axis during the flowering period. The adaptive significance of flexistyly has been interpreted as a floral mechanism for outcrossing, but it may also function to reduce sexual interference in which styles and stigmas impede the pollen export. Here these two explanations of flexistyly were tested in Alpinia blepharocalyx through a hand-pollination experiment. Hand-pollinations were performed in two temporal morphs and consisted of two sequential pollination treatments, namely self-pollination in the morning and inter-morph pollination in the afternoon (treatment 1) or conversely inter-morph pollination in the morning and self-pollination in the afternoon (treatment 2), and two simultaneous self- and inter-morph cross-pollination treatments either in the morning (treatment 3) or in the afternoon (treatment 4). Seed paternity was then determined to assess relative success of self- versus cross-pollen using allozyme markers. In the sequential pollination treatments, whether the stigmas of recipients are receptive in the morning is crucial to the success of the pollen deposited. When the cataflexistylous (protandrous) morph served as pollen recipient, early-arriving pollen in the morning can sire only a very small proportion (<15%) of seeds because the stigmas were then unreceptive. However, when the anaflexistylous (protogynous) morph served as pollen recipient, early pollen did gain a large competitive advantage over the late pollen, particularly when cross-pollen arrived first. Simultaneous self- and inter-morph cross-pollination indicated that outcross-pollen is more competitive than self-pollen on receptive stigmas. Differential maturing of male and female organs in Alpinia blepharocalyx is sufficient for selfing avoidance, obviating the need for style movements. Instead, the upward style curvature of the cataflexistylous morph in the morning and the anaflexistylous morph in the afternoon most likely represents a means of reducing interference with pollen export.

Behavioural mechanisms of invasion and displacement in Pacific island geckos ( Hemidactylus)

The house gecko Hemidactylus frenatus is currently displacing an ecologically similar, all-female parthenogenetic gecko H. garnotii on a global scale. We tested the previously proposed hypotheses that resource competition is responsible for this displacement, and that competitive interference occurs through male aggression. We quantified consumption of insect resources and behavioural interactions in dyads and triads composed of different combinations of sexes and species. Geckos consumed fewer insects when in pairs than when they were alone, indicating general evidence of resource competition. However, resource consumption of parthenogenetic H. garnotii was not negatively affected by the presence of invasive H. frenatus, suggesting that resource competition is not the primary mechanism of displacement. Males were aggressive towards conspecific males, but showed little aggression towards conspecific females and parthenogenetic females; females and parthenogens displayed little aggression. Male H. frenatus courted and copulated with both conspecific and heterospecific females in dyads and in triads and, by some measures, showed a preference for larger H. garnotii females. When paired with females or parthenogens, males consumed fewer resources because they turned their attention to courtship. Evidence of interspecific courtship suggests that sexual interference may be a more likely mechanism of displacement. Our results exclude the possibility that courtship decreases resource consumption in H. garnotii, but further study is required to determine whether interspecific mating disrupts parthenogenetic reproduction. This study demonstrates the importance of testing commonly invoked mechanisms of invasion and displacement by quantifying individual behaviour in an experimental setting.

COURTSHIP BEHAVIOR IN THE ALPINE NEWT TRITURUS ALPESTRIS AT TWO DIFFERENT DENSITIES OF MALES

The aim of this laboratory experiment was to examine courtship behavior and reproductive success under two different perceived male densities in the Alpine newt (Triturus alpestris). Male behavioral patterns were similar at unbiased and male-biased operational sex ratios (OSR). Although the exhibition of luring behaviors is risky in the presence of other males, no difference in the frequencies of displays was found at the two male densities. Similarly, the responsiveness of females towards males and the success rate of the encounters (i.e., spermatophore transfer) were not explained by the OSR. Our results show that courting Alpine newts do not change their courtship patterns when other males are present and do not interact directly. However they are not necessarily opposed to those of previous experiments showing sexual interference and female aversion in male-biased OSR with possibility of interactions. These observations suggest that the evolution of courtship behavior may not be driven by the risk of sexual interference with other males prior to potential physical contact and that the benefits of breeding regardless of OSR can overcome the risk of competition at male-biased OSR.

Self‐pollen on a stigma interferes with outcrossed seed production in a self‐incompatible monoecious plant, Akebia quinata (Lardizabalaceae)

Summary Akebia quinata Decaisne is a monoecious woody vine. As the plants are self‐incompatible, separation of sex functions between flowers may function to avoid sexual interference rather than to avoid inbreeding depression. To investigate whether self‐pollen on stigmas affects outcrossed seed production in A. quinata, we carried out an artificial pollination experiment in which self‐pollination was conducted either simultaneously with, or 24 h before, cross‐pollination. Compared with cross‐pollination, fruit set was significantly reduced by prior self‐pollination. Simultaneous self‐ and cross‐pollination also reduced fruit production. Overall, self‐pollen on a stigma reduced seed production by 85% compared with cross‐pollination. Growth rate of self‐pollen tubes in carpels did not differ from that of cross‐pollen tubes, and self‐pollen tubes could reach ovules. This indicates that A. quinata has late‐acting self‐incompatibility, which may cause sexual interference if self‐pollination occurs. These results support the idea that monoecy in A. quinata functions to avoid sexual interference, which imposes a fitness cost, at least on female function.

On the mechanism of floral shifts in speciation: gained pollination efficiency from tongue- to eye-attachment of pollinia in Platanthera (Orchidaceae)

This work explores the mechanism of floral shifts that may result in speciation. The model organisms chosen were the moth-pollinated pollinator-limited orchid species Platanthera bifolia and P. chlorantha. P. bifolia exhibits tongue-attachment of pollinia on pollinators, a character state that has been found previously to be ancestral. The close relative P. chlorantha exhibits the derived state of eye-attachment of pollinia on pollinators. We reasoned that differences between the species in pollination efficiency could give insights into the mechanism of floral shifts and thus cladogenesis. Four populations per species were investigated. In three populations, where the species were growing intermixed and were sharing pollinators, there was significant difference in the pollen export and import efficiency per visit-night (night with pollen export and/or import) between the two species. P. bifolia exported pollinia more efficiently but imported pollen less efficiently than did P. chlorantha. Pollen import was 1.7–4 times faster in P. chlorantha (eye-attachment) than it was in P. bifolia (tongue-attachment). P. chlorantha had a lower risk of interference between pollen import and export. An increase in fitness through greater speed and efficiency of pollen import due to an enlargement of the stigmatic surface and a reduction in the risk of sexual interference may therefore be mechanisms of the floral shift from tongue- to eye-attachment of pollinia on pollinators.

Heterostyly: speciation within a species

AbstractAlmost all organisms in nature show nonrandom mating to different degrees. Two extreme results of nonrandom mating are speciation and sexual differentiation. Heterostyly is a form of sexual differentiation considered to have evolved to resolve conflicts between male and female functions of hermaphrodite flowers. Our study examines necessary and sufficient conditions for establishment of heterostyly using a configuration individual‐based model. Previous models assume invasion of a mutant phenotype into a population with monomorphic wild phenotype. In contrast, our model demonstrates that heterostyly can be established from a population with continuous phenotypic variation, a proposition that requires simpler assumptions than the previous hypotheses. Results of our simulation show that genetic linkage between stigma and anther heights is essential for establishment of heterostyly. Dominance effects on the genes for stamen or stigma heights are not necessary, but they promote evolution of heterostyly. Probability of evolution of heterostyly also depends on the functional relationship between stigma–anther distance and strength of sexual interference, and the distance and probability of pollen deposition success. Parallelity and difference between speciation and sexual differentiation are also discussed.

Effect of Rival Males on the Courtship of Paedomorphic and Metamorphic Triturus alpestris (Amphibia: Salamandridae)

Current theories on the alternative mating tactics suppose that individuals may opt for particular behavioral patterns depending of their morphological status. Facultative paedomorphosis in newts and salamanders is a suitable process to explore this question because it implies the coexistence of two different morphological morphs differing by the presence of gills and epigamic traits. The aim of this study was to find out whether paedomorphs and metamorphs use similar tactics to attract mates in the presence of a rival and whether there are differences in sexual activity and success between alternative morphs. Sexual interactions in triadic encounters were staged and analyzed in a standardized experimental design. The two kinds of males did not differ in terms of sexual activity, spermatophore deposition or female responsiveness. Both rival paedomorphic and metamorphic males exhibited sexual interference, but in most encounters, intruders just disturbed the courting pair. Sperm transfer success was lower in triadic encounters than in dyadic encounters. These results illustrate that intermorph breeding also occurs in the presence of competitors but that the success rate of the newts is considerably decreased in such competitive situations. Moreover, newts do not use alternative reproductive tactics depending on their status (i.e., paedomorph or metamorph).

Etiological Correlates of Vaginismus: Sexual and Physical Abuse, Sexual Knowledge, Sexual Self-Schema, and Relationship Adjustment

This study investigated the role of sexual and physical abuse, sexual self-schema, sexual functioning, sexual knowledge, relationship adjustment, and psychological distress in 87 women matched on age, relationship status, and parity and assigned to 3 groups- vaginismus, dyspareunia/vulvar vestibulitis syndrome (VVS), and no pain. More women with vaginismus reported a history of childhood sexual interference, and women in both the vaginismus and VVS groups reported lower levels of sexual functioning and a less positive sexual self-schema. Lack of support for traditionally held hypotheses concerning etiological correlates of vaginismus and the relationship between vaginismus and dyspareunia are discussed.

Necrophilia: Case Report and Consideration of Legal Aspects

A criminal investigation arising from a break-in at the premises of a funeral director indicated that sexual interference with several corpses had taken place. The forensic issues regarding consent to examine the bodies and the nature of the crimes committed, with consideration of international law in this field, are discussed. Necrophilia is an issue that has not been the subject of legal statute in the United Kingdom to date, although this issue is currently under consideration by the Home Office in proposals to reform the law on sexual offences

Sexual interference of the floral kind.

Floral hermaphroditism results in conflicts and compromise in the parental roles of plants during pollination and mating. A potential cost of hermaphroditism is sexual interference between maternal and paternal functions resulting in gamete wastage and reduced fitness. Sexual interference may or may not be associated with self-pollination. In cases where self-pollination occurs, ovule or pollen discounting may reduce mating opportunities. Here I describe forms of sexual interference in flowering plants, distinguishing whether physical or biochemical interactions are involved and whether fitness costs associated with gamete wastage arise from intra-floral versus inter-floral processes. I review the limited experimental evidence for interference between sex functions and evaluate the hypothesis that some floral adaptations usually interpreted as anti-selfing mechanisms may serve an alternative function in reducing mating costs arising from this form of sexual conflict.

Pre-copulatory ejaculation solves time constraints during copulations in marine iguanas

When animals compete for copulations, large body size often implies high mating success. Small males may, however, compensate for their competitive disadvantage by special adaptive traits. This is the case in marine iguanas, iguanid reptiles of the Galapagos archipelago. In marine iguanas, females copulate only once per season. During copulations, males needed 2.8—3.1 min to initiate ejaculation. Large territorial males copulated long enough (more than 3.1 min) to achieve ejaculations in 95% of copulations, even when disturbed. Small males were separated from females by rival males in 29% of copulations before the start of ejaculation. Small males nevertheless fertilized females using prepared viable ejaculate, which was kept in readiness in hemipenis pouches and transferred into the female cloaca at intromission. This tactic increased the mating success of small males by 41 %. This tactic demonstrates the adaptive significance of a trait which is functionally equivalent to non-ejaculatory ‘masturbation’, and appears to be unique for vertebrates. However, similar phenomena have occasionally been observed, but mostly lacked functional explanation. An ‘ejaculation-in-advance’ could occur in many taxa in which there is size-dominance hierarchy and sexual interference, but this remains to be determined.

Female Sexual Interference in the Smooth Newt, Triturus vulgaris vulgaris

AbstractCompetition between unmated females for males was observed in the smooth newt, T. vulgaris, during the early part of the breeding season. Females interfered at the spermatophore‐transfer stage of courtship, preventing a rival female from picking up the sperm mass. Interference often resulted in the rival female abandoning the courtship encounter. In many of the encounters (70%), the interfering female was inseminated. However, interference between females was not observed after the commencement of ovulation.By contrast, the incidence of sexual interference between males was low during the preovulatory period and increased significantly post‐ovulation.Sexual interference in newts and salamanders has previously only been observed between males. During the greater part of the breeding season, when females are ovipositing, eggs are the limiting resource and males compete for access to receptive females. However, this study suggests that early in the breeding season, prior to commencement of ovulation, the limiting resource may temporarily be sperm, due to the physiological constraint of spermatophore production. This may lead to female competition for mates.

A field study of reproductive interactions in Bosca's newt, Triturus boscai

AbstractObservations of a free-living population of Bosca's newt, Triturus boscai, show that courtship behaviour in nature is similar to the behaviour observed in earlier laboratory studies. Complementary evidence was obtained on the behaviour called flick, which is sometimes inserted at the end of the static display phase, and may be viewed as an equivalent behaviour to the retreat display of the other small-bodied newt species. Sexual interference in the natural population was mainly caused by males. Two characteristic male behaviour patterns were recognised, the waiting position and the push-tail. Females tend to withdraw from situations of interference. Courtship sequences solely consisting of orientation and spermatophore transfer phases, so-called short-circuit sequences, may be interpreted as a male strategy to avoid the very severe male-to-male interference that exists in a wild population.

Return-benefit spite hypothesis: An explanation for sexual interference in stumptail macaques (Macaca arctoides)

Sexual interference behavior (the phenomenon of intervening with the matings of others) appears selfish in that its primary function seems to be that of improving one's reproductive fitness relative to others. In stumptail macaques (Macaca arctoides), interference may be spiteful, and may contribute to the receipt of a return benefit. This is the focus of this paper.

Predation Risk Affects Mate Choice in a Gobiid Fish

Predation Risk Affects Mate Choice in a Gobiid Fish

Courtship Behavior of the Small-Mouthed Salamander (Ambystoma Texanum): the Effects of Conspecific Males On Male Mating Tactics

Abstract1. The courtship behavior of A. texanum consisted of a rapid nudging period followed by males producing many spermatophores, some of which were picked up by the female. Neither amplexus or leading by the male were integral components of courtship. Consequently, proposed geographic variation in A. texanum courtship remains unsubstantiated. 2. Courtship behavior of A. texanum and A. barbouri (formerly pond and stream form A. texanum, respectively) is very similar; only the location of courtship and perhaps the frequency of sexual interference tactics are different for these two sibling species. 3. A. texanum courtship is rapid, males produce large numbers of spermatophores per courtship and invest little courtship time per spermatophore, and intermale competition is extreme. 4. Male A. texanum promote their sexual success using sexual interference behavior (e.g. covering other spermatophores with their own) and to a lesser degree sexual defense behavior (e.g. forcefully nudging rival males). 5. Male sexual success is primarily enhanced directly - A. texanum males increase the number of spermatophores produced when at least two other males are courting the same female. The temporal allocation of these additional spermatophores is adaptive only if males are maximizing the number of ejaculates per female or breeding typically occurs in polygamous aggregations.

Sexual strategies in the newts Triturus Cristatus and Triturus Marmoratus

Courtship display characteristics are described and compared for the newts Triturus cristatus and T. marmoratus and patterns of male competitive behaviour are recognized. In interpreting the data, the operational sex ratio has to be taken into account, which was highly biased towards males in both species, more in T. marmoratus than in T. cristatus. When sexual active, males of cristatus had more encounters than males of marmoratus, whereas the latter spent more time residing mating places. The male’s display towards a female differed in time structure, variability and in behaviour characteristics. T. marmoratus display follows a fixed pattern; males succeeded better in restraining a female than males cristatus did. Courting males cristatus allowed other males to intrude. Malemale encounters were longer and playful in T. cristatus, more violent in T. marmoratus. Comparison with data from the literature indicates that courtship of T. marmoratus has more features in common with that of T. vittatus than it has with the courtship of T. cristatus. It is suggested that in the course of evolution T. marmoratus adopted a strategy of Sexual Defense by means of territoriality and overt fighting, whereas T. cristatus in contrast adopted a strategy of Sexual Interference by female mimicry. Male display components that played a major role during the adaptation of competitive strategy are identified as the “whip” behaviour in T. marmoratus and the “rocking” behaviour in T. cristatus.

Male copulation frequency and female competition for fertilizations in a promiscuous brood parasite, the Pin‐tailed Whydah Vidua macroura

Male Pin‐tailed Whydahs Vidua macroura copulate infrequently and terminate most courtship displays, even when females are highly receptive. Female sexual interference is aimed at preventing other females from copulating, and is nearly always successful.

Sexual interactions in red-spotted newt populations

Two alternative reproductive tactics (amplexus and spermatophore transfer interference) and three sexual interference tactics (spermatophore transfer interference, pseudofemale behaviour, amplexus interference) are described for male red-spotted newts, Notophthalmus viridescens. The two reproductive tactics yield equal insemination rates for males displaying these behaviours. The three sexual interference tactics decrease the potential fitness of amplectic males either directly, by displacing them from receptive females and/or duping them into fruitless spermatophore depositions, or indirectly, by increasing the time spent in amplexus with no concomitant increase in probability of successful insemination.

Anorexia and Bulimia in Anorexia Nervosa

Seventeen fasting patients with anorexia nervosa and 15 who also binged were compared in terms of their psychosocial functioning and associated psychiatric symptomatology, using the Delusions Symptoms and States Inventory (Foulds & Bedford, 1975). Both groups scored very highly on the state of anxiety, depression, and elation sets of the DSSI, but less highly on the compulsive and ruminative symptoms sets and on the phobic dissociative and conversion symptom sets. The bingeing anorexic group was significantly older and heavier than the fasting group and experienced more feelings of self-harm and guilt. The bingeing group reported sexual interference during childhood, and currently experienced a desire to vomit during sexual activity to a significantly greater degree than the fasting group.