Mating Behaviour (mating + behaviour)

Distribution by Scientific Domains
Distribution within Life Sciences

Kinds of Mating Behaviour

  • female mating behaviour


  • Selected Abstracts


    Male-biased size dimorphism in ichneumonine wasps (Hymenoptera: Ichneumonidae) , the role of sexual selection for large male size

    ECOLOGICAL ENTOMOLOGY, Issue 3 2005
    Tiit Teder
    Abstract., 1.,Sexual differences in body size are expected to evolve when selection on female and male sizes favours different optima. 2.,Insects have typically female-biased size dimorphism that is usually explained by the strong fecundity advantage of larger size in females. However, numerous exceptions to this general pattern have led to the search for selective pressures favouring larger size in males. 3.,In this study, the benefits of large size were investigated in males of four species of ichneumonine wasps, a species-rich group of parasitoids, many representatives of which exhibit male-biased size dimorphism. 4.,Mating behaviour of all ichneumonine wasps are characterised by pre-copulatory struggles, in the course of which males attempt to override female reluctance to mate. A series of laboratory trials was conducted to study the determinants of male mating success. 5.,A tendency was found for larger males as well as those in better condition to be more successful in achieving copulations. Size dimorphism of the species studied, mostly male-biased in hind tibia length but female-biased in body weight, indicates that sexual selection in males favours longer bodies and appendages rather than larger weight. 6.,The qualitative similarity of the mating patterns suggests that sexual selection cannot completely explain the considerable among-species differences in sexual size dimorphism. 7.,The present study cautions against using various size indices as equivalents for calculating sexual size dimorphism. 8.,It is suggested that female reluctance in ichneumonine wasps functions as a mechanism of female mate assessment. [source]


    Sex in a cyclical parthenogen: mating behaviour of Chydorus sphaericus (Crustacea; Branchiopoda; Anomopoda)

    FRESHWATER BIOLOGY, Issue 12 2006
    KAY VAN DAMME
    Summary 1. We describe the interactions during mating in Chydorus sphaericus, a cyclical parthenogenetic anomopod. Mating behaviour is more complex than previously assumed, with evidence for a diffusible chemical to which males react at the onset of mating, for reproductive isolation, and for postcopulatory mate guarding. 2. During mating, the male and female form a ,mating cross' that may be maintained for several hours, while copulation itself typically lasts less than a minute. Furthermore, males invariably attach to the right valve of females. Copulation involves intromission of the postabdomen between the valves, so that the gonopores approach the left ovarium. 3. This behaviour is reflected in the morphology of both sexes: males have a specialised anterior valve margin, postabdomen, first limb and rostrum, under selective pressure for successful mate guarding and copulation, while gamogenetic females have asymmetric ovaries, and a species-specific setulation of the valves. Males of the structurally related Chydorus ovalis react to the presence of C. sphaericus, but fail to dock to females, suggesting a lock-antilock element in the reproductive isolation of both species. 4. The morphological and ethological adaptations in C. sphaericus suggest that there is a strong selective pressure on mating behaviour in this cyclical parthenogen and specifically towards the formation of the ,mating cross'. [source]


    Mating behaviour of the ,cosmopolitan' species Phyllognathopus viguieri (Copepoda: Harpacticoida) and its systematical significance

    JOURNAL OF ZOOLOGICAL SYSTEMATICS AND EVOLUTIONARY RESEARCH, Issue 4 2008
    D. Königshoff
    Abstract The mating behaviour was studied and recorded on video with individuals of four cultures of Phyllognathopus viguieri from different populations obtained from the interstitial water of a slow sand filter near the river Ruhr (Germany) (Ruhr population), from a compost heap in Bethesda (Maryland, USA) (Maryland population), from a rain gauge in Windsor Campbell farm (Jamaica) (Jamaica population), and a tree trunk with moss in a forest in the municipality of Rio de Janeiro (Brazil) (Brazil population). The mating behaviour was divided into the well-known initial phase, copula phase and postcopulatory mate guarding phase. An additional phase prior to the initial phase serves to recognize the female, the recognition phase. The mating behaviour is identical in the males of the Jamaica and Brazil populations of P. viguieri. A postcopulatory mate guarding phase is not found in these two groups. Here, we refute the hypothesis, that a postcopulatory mate guarding phase is found in taxa in which only adult males grasp adult females. The males of the Ruhr and Maryland populations differ from each other in their mating behaviour. Generally, the males of all four populations do not mate with fertilized females which are equally unattractive to the males, i.e., females mate only once in their lifetime to produce offspring. These results corroborate the view that the different populations of P. viguieri do not belong to a single cosmopolitan species. Zusammenfassung Das Kopulationsverhalten wurde an Vertretern aus vier Populationen von Phyllognathopus viguieri mit unterschiedlicher geographischer Herkunft mit Videoaufzeichnung untersucht. Die Tiere stammen aus dem Grundwasser der Ruhr (Langsamsandfilter) Deutschland (Ruhr-Population), aus Moospolstern im städtischen Wald von Rio de Janeiro, Brasilien (Brazil-Population), aus einem Komposthaufen in Bethesda, Maryland, USA (Maryland-Population) und aus einer Zisterne der Windsor Campbell farm, Jamaika (Jamaica-Population). Das Kopulationsverhalten kann in wie bereits bekannt Initialphase, Kopulaphase und Postkopulaphase eingeteilt werden. Während der Initialphase findet keine Balz statt. Als zusätzliche Phase findet vor der Initialphase eine Prüfphase statt, die dem Erkennen des Weibchens dient. Es konnte festgestellt werden, daß die Vertreter der vier Populationen sich in Bezug auf ihr Kopulationsverhalten voneinander unterscheiden. Das Kopulationsverhalten der Tiere aus Jamaika und Brasilien war identisch, sowohl die Dauer der einzelnen Phasen, als auch das Verhalten der einzelnen Versuchsindividuen. Bei ihnen trat keine Postkopulaphase auf. Bei den Tieren der Ruhr- und der Marylandpopulation trat eine Postkopulaphase von unterschiedlicher Dauer auf. Auch das Fortpflanzungsverhalten der Männchen war unterschiedlich. Die in der Literatur vertretene Hypothese, dass bei Taxa, in denen die Männchen nur adulte Weibchen greifen, eine Postkopulaphase vorkommt, wird in dieser Studie widerlegt. Die Weibchen kopulieren nur einmal in ihrem Leben, was für ihre gesamte Reproduktion ausreichend ist. Männchen kopulieren in der Regel nicht mit bereits begatteten Weibchen. Bereits begattete Weibchen zeigen ein Abwehrverhalten, um die Männchen an der Anheftung der Spermatophore zu hindern. Die Spermatophore wird ohne Hilfe der Schwimmbeine übertragen. Die Befestigung der Spermatophore am Genitalfeld des Weibchens geschieht mit einer Kittsubstanz, die vom Männchen abgegeben wird. Die Individuen der Ruhr- und der Marylandpopulation zeigen trotz einer bei beiden vorkommenden Postkopulaphase unterschiedliches Fortpflanzungsverhalten. Wir schließen daraus, dass sie unterschiedlichen biologischen Arten angehören. Die Individuen der Jamaika- und Brazil-Populationen sind einer Art zuzuordnen, die sich von diesen beiden Arten unterscheidet. Die in dieser Arbeit gemachten Beobachtungen sind eine Bestätigung dafür, dass P. viguieri keine kosmopolitische Art ist, sondern dass es sich tatsächlich um eine Gruppe kryptischer valider Arten handelt. [source]


    Mating behaviour and alternative oviposition sites for male eggs in the heteronomous hyperparasitoid Coccophagus gurneyi Compere (Hymenoptera: Aphelinidae)

    AUSTRALIAN JOURNAL OF ENTOMOLOGY, Issue 1 2001
    GT Parkes
    Abstract The aphelinid parasitoid Coccophagus gurneyi Compere has unusual sex-related host relationships. Females are diploid and develop internally within mealybugs Pseudococcus calceolariae (Maskell). Males, in contrast, are haploid and hyperparasitic, developing on primary parasitoid larvae within the mealybugs. Furthermore, males have been claimed to be capable of either internal or external development, depending on the precise site of deposition of the haploid egg. This diversity of developmental pathways could indicate the existence of a sibling-species complex. We therefore quantified the mating and ovipositional behaviour of C. gurneyi, for comparison with that of an undescribed sibling species. We also checked whether the females deposit male eggs in alternative sites. The pattern of mating was found to be typical of mating behaviour in Coccophagus spp. and was consistent among all mating pairs, suggesting that the colony comprised one species. Further, the mating behaviour was significantly different from that of the undescribed sibling species. The site of male egg deposition varied and is apparently dictated by two factors; whether the mealybug is parasitised and, if so, the size of the parasitoid it contains. If the mealybugs were unparasitised or if the parasitoids within the mealybugs were small (< 0.53 mm), male eggs were deposited within the mealybug haemocoel. If the parasitoids were large (> 1.05 mm), male eggs were deposited within the parasitoids. These results support the claim of alternate host relationships and developmental pathways within males of C. gurneyi. [source]


    Behavioural changes in Schistocerca gregaria following infection with a fungal pathogen: implications for susceptibility to predation

    ECOLOGICAL ENTOMOLOGY, Issue 3 2001
    Steven Arthurs
    Summary 1. Field observations have indicated that infection of locusts and grasshoppers by the fungal entomopathogen Metarhizium anisopliae var. acridum may result in a substantial increase in the host's susceptibility to predation, before death is caused directly by the disease. 2. Laboratory experiments were conducted to examine how the behaviour of the desert locust Schistocerca gregaria Forskål changes following infection by M. anisopliae var. acridum to explore some potential mechanisms underlying this phenomenon. 3. In the first experiment, which involved monitoring general locust activity in small cages throughout the disease incubation period, infected locusts were observed to increase locomotion and bodily movement from 3 days after infection until death (average survival time of 11 days). There was some evidence of reduced feeding and mating behaviour following infection. 4. In a second experiment, locusts were exposed individually to a simulated predator attack and the initiation and strength of any escape responses were measured. Infected locusts were observed to have a reduced escape capability (both the propensity to escape and the strength of the response). In contrast to the relatively early changes in general activity observed in the first experiment, this was only apparent at the late stages of infection shortly before death. 5. Both an increase in movement and general apparency early in the infection process, and reduced escape capability late on, suggest mechanisms whereby the susceptibility of locusts and grasshoppers to predation might be enhanced following infection with M. anisopliae var. acridum. [source]


    Scent of a Woman , The Effect of Female Presence on Sexual Cannibalism in an Orb-Weaving Spider (Araneae: Araneidae)

    ETHOLOGY, Issue 7 2009
    Stefan H. Nessler
    Post-mating sexual cannibalism occurs as a regular element of mating behaviour in a number of spider species. Frequencies of cannibalism, however, are highly variable between and within species. In Argiope bruennichi, males apparently differ in their motivation to escape a female attack but causes for this variability are unknown. We observed that the probability of sexual cannibalism is positively correlated with male age, i.e. the number of days that passed between male maturation and copulation. The mating season in this species is short with 3,4 wk and males mostly mature days before the females, whose maturation phase is longer. Consequently, as the season progresses, the availability of virgin females increases, quickly reaches a peak and then rapidly declines. In addition, the age of still unmated males increases with the season and both of these factors can potentially affect the degree of sexual cannibalism. To separate these factors, males were collected in their penultimate stage and kept until mating either with or without contact to female pheromones. Thereby, we experimentally manipulated the male's perception of female presence. Within each treatment, we formed three male age groups: (1) 2,6 d, (2) 12,16 d and (3) 22,28 d. Our results demonstrate that the probability of cannibalism was independent of male age but was explained by the treatment of males: males exposed to virgin female pheromones were significantly more likely to be cannibalised than males that were kept without female pheromones. This suggests that males change their reproductive strategy according to perceived mating prospects. [source]


    The dark triad: Facilitating a short-term mating strategy in men

    EUROPEAN JOURNAL OF PERSONALITY, Issue 1 2009
    Peter K. Jonason
    Abstract This survey (N,=,224) found that characteristics collectively known as the Dark Triad (i.e. narcissism, psychopathy and Machiavellianism) were correlated with various dimensions of short-term mating but not long-term mating. The link between the Dark Triad and short-term mating was stronger for men than for women. The Dark Triad partially mediated the sex difference in short-term mating behaviour. Findings are consistent with a view that the Dark Triad facilitates an exploitative, short-term mating strategy in men. Possible implications, including that Dark Triad traits represent a bundle of individual differences that promote a reproductively adaptive strategy are discussed. Findings are discussed in the broad context of how an evolutionary approach to personality psychology can enhance our understanding of individual differences. Copyright © 2008 John Wiley & Sons, Ltd. [source]


    Sex in a cyclical parthenogen: mating behaviour of Chydorus sphaericus (Crustacea; Branchiopoda; Anomopoda)

    FRESHWATER BIOLOGY, Issue 12 2006
    KAY VAN DAMME
    Summary 1. We describe the interactions during mating in Chydorus sphaericus, a cyclical parthenogenetic anomopod. Mating behaviour is more complex than previously assumed, with evidence for a diffusible chemical to which males react at the onset of mating, for reproductive isolation, and for postcopulatory mate guarding. 2. During mating, the male and female form a ,mating cross' that may be maintained for several hours, while copulation itself typically lasts less than a minute. Furthermore, males invariably attach to the right valve of females. Copulation involves intromission of the postabdomen between the valves, so that the gonopores approach the left ovarium. 3. This behaviour is reflected in the morphology of both sexes: males have a specialised anterior valve margin, postabdomen, first limb and rostrum, under selective pressure for successful mate guarding and copulation, while gamogenetic females have asymmetric ovaries, and a species-specific setulation of the valves. Males of the structurally related Chydorus ovalis react to the presence of C. sphaericus, but fail to dock to females, suggesting a lock-antilock element in the reproductive isolation of both species. 4. The morphological and ethological adaptations in C. sphaericus suggest that there is a strong selective pressure on mating behaviour in this cyclical parthenogen and specifically towards the formation of the ,mating cross'. [source]


    MSI-1, a neural RNA-binding protein, is involved in male mating behaviour in Caenorhabditis elegans

    GENES TO CELLS, Issue 11 2000
    Akinori Yoda
    Neural RNA-binding proteins are thought to play important roles in neural development and the functional regulation of postmitotic neurones by mediating post-transcriptional gene regulation. RNA-binding proteins belonging to the Musashi family are highly expressed in the nervous system; however, their roles are poorly understood. We identified a Caenorhabditis elegans Musashi homologue, MSI-1, whose RNA-recognition motifs show extensive similarity to those of Drosophila and vertebrate Musashi proteins. We isolated a msi-1 mutant and found males with this mutation to have a mating defect. C. elegans male mating behaviour includes a distinct series of steps: response to contact, backing, turning, vulva location, spicule insertion, and sperm transfer. msi-1 is required for the turning and vulva location steps. Like other Musashi family members, MSI-1 is expressed specifically in neural cells, including male-specific neurones required for turning and vulva location. However, msi-1 was not expressed in proliferating neural progenitors in C. elegans, unlike the Musashi family genes in other systems. Our results suggest that msi-1 is expressed specifically in postmitotic neurones in C. elegans. msi-1 is required for full development of male mating behaviour, possibly through regulation of msi-1 expressing neurones. [source]


    Altered mating behaviour in a Cry1Ac-resistant strain of Helicoverpa armigera (Lepidoptera: Noctuidae)

    JOURNAL OF APPLIED ENTOMOLOGY, Issue 5 2008
    X. C. Zhao
    Abstract Randomness of mating between susceptible and resistant individuals is a major factor that closely relates to the refuge strategy of resistance management for Helicoverpa armigera (Hübner) to Bacillus thuringiensis cotton. The mating behaviour of Cry1Ac-susceptible and Cry1Ac-resistant strains of H. armigera was compared to investigate the randomness of their mating. The percentage of mating was lower for Cry1Ac-resistant H. armigera compared with that of the susceptible strain under both no-choice and multiple-choice conditions. The low percentage of mating in the resistant strain indicates a reduced incidence of successful mating. The percentage of spermatophore-containing mated female H. armigera in the crossing of susceptible females × resistant males was significantly lower than in the crossing of resistant females × susceptible males, but the observed mating frequencies of these two types of cross were similar to each other. This indicates that resistant males reduce the incidence of mating paternity more than they do their mating frequency. The percentages of heterogametic matings (susceptible females × resistant males, resistant females × susceptible males) in the multiple-choice experiment were lower than those of homogametic matings (susceptible × susceptible, resistant × resistant) on peak mating nights. However, the difference between heterogametic and homogametic mating was not significant, indicating that there was a random mating between susceptible and resistant strains. The results presented here do not reflect reality in mating associated with Cry1Ac resistance but can provide insight into variable expression. [source]


    Effects of sex pheromone in electrostatic powder on mating behaviour by Lobesia botrana males

    JOURNAL OF APPLIED ENTOMOLOGY, Issue 5 2007
    C. Nansen
    Abstract:, In laboratory trials, mating behaviour of males of Lobesia botrana Den. and Schiff. (Lep., Tortricidae) was investigated after treatment with an electrostatically chargeable powder, EntostatTM. Male moths were powdered with either blank Entostat or Entostat containing sex pheromone. Significantly more Entostat adhered to L. botrana males when sex pheromone was added to the powder compared with blank Entostat. Powdering male moths with Entostat, with or without sex pheromone, caused a significant reduction in antennal response when antennae were placed 2 cm away in downwind direction, while there was little effect when antennae were placed 25,100 cm from the EAG in downwind direction. In a flight study, powdering males of L. botrana caused significant increase in time before flight initiation and reduction in proportion of males making contact with calling females compared with untreated males. In a mating experiment in Petri dishes (to minimize required search time to locate female), significantly fewer females mated successfully (based on dissection of bursa copulatrix) when males had been treated with pheromone-loaded powder. Overall, powdering males of L. botrana caused considerable suppression of mating behaviour on various levels, and these suppressing effects were increased after adding sex pheromone to Entostat. [source]


    Male and female Silene latifolia plants differ in per-contact risk of infection by a sexually transmitted disease

    JOURNAL OF ECOLOGY, Issue 1 2001
    Oliver Kaltz
    Summary 1,Behavioural, physiological or immunological constraints often render one sex more susceptible to parasites, thereby potentially generating sex-specific trade-offs between traits associated with infection risk and other life-history characters. 2,The fungal pathogen Microbotryum violaceum systemically infects the dioecious plant Silene latifolia when pollinators deposit fungal spores on the flowers of healthy plants. Male plants produce many short-lived flowers, whereas females produce few flowers that remain connected with the plant after fertilization. We investigated how variation in flower production and flower longevity affects the infection risk for males and females. 3,In glasshouse experiments, we varied the number of flowers inoculated (4 vs. 16 per plant) with spores and the time until these flowers were removed (1 or 2 days for both sexes, 14 days for females only). We also measured the longevity of male flowers receiving simulated visits, with or without spores, to test for an abscission response to visitation and/or contamination. In a field survey, we measured male and female disease prevalence in 17 natural populations. 4,Varying the number of inoculated flowers did not affect infection probability, but females retaining inoculated flowers for 14 days became diseased more often (20.0%) than did plants with flowers removed within 2 days (7.3%). 5,Males that had dropped more inoculated flowers prematurely were more likely to remain uninfected. Spore-bearing visits shortened male flower longevity (38.4 ± 2.8 h) relative to non-spore visits (47.9 ± 5.2 h). 6,Female field disease prevalence (19.7 ± 3.5%) was higher than that of males (14.3 ± 2.6%), especially in populations with a high disease incidence. 7,Continuing physical connection during fruit ripening appears to increase invasion time and thus the per-contact infection risk in females. This is consistent with higher female field prevalences, although other explanations, unrelated to disease transmission, are possible. These results illustrate how interactions between plant reproductive behaviour and pollinator activity may affect disease spread. Female mating behaviour may evolve towards lower attractiveness to pollinators to minimize infectious contacts, while males can afford to be more promiscuous with an attractive, but disposable, floral display. [source]


    From kissing to belly stridulation: comparative analysis reveals surprising diversity, rapid evolution, and much homoplasy in the mating behaviour of 27 species of sepsid flies (Diptera: Sepsidae)

    JOURNAL OF EVOLUTIONARY BIOLOGY, Issue 11 2009
    N. PUNIAMOORTHY
    Abstract Our understanding of how fast mating behaviour evolves in insects is rather poor due to a lack of comparative studies among insect groups for which phylogenetic relationships are known. Here, we present a detailed study of the mating behaviour of 27 species of Sepsidae (Diptera) for which a well-resolved and supported phylogeny is available. We demonstrate that mating behaviour is extremely diverse in sepsids with each species having its own mating profile. We define 32 behavioural characters and document them with video clips. Based on sister species comparisons, we provide several examples where mating behaviour evolves faster than all sexually dimorphic morphological traits. Mapping the behaviours onto the molecular tree reveals much homoplasy, comparable to that observed for third positions of mitochondrial protein-encoding genes. A partitioned Bremer support (PBS) analysis reveals conflict between the molecular and behavioural data, but behavioural characters have higher PBS values per parsimony-informative character than DNA sequence characters. [source]


    Polyandry in coal tits Parus ater: fitness consequences of putting eggs into multiple genetic baskets

    JOURNAL OF EVOLUTIONARY BIOLOGY, Issue 3 2007
    T. SCHMOLL
    Abstract Females of many species mate with multiple males within a single reproductive cycle. One hypothesis to explain polyandry postulates that females benefit from increasing within-brood genetic diversity. Two mechanisms may render sire genetic diversity beneficial for females, genetic bet-hedging vs. non-bet-hedging. We analysed whether females of the socially monogamous coal tit (Parus ater) benefit via either of these mechanisms when engaging in extra-pair (i.e. polyandrous) mating. To obtain a measure of within-brood genetic diversity as a function of paternal genetic contributions, we calculated a sire diversity index based on the established Shannon,Wiener Index. In 246 broods from two consecutive years, sire genetic diversity had no effect on either the mean or the variance in brood fitness measured as offspring recruitment within 4 years after birth. The hypothesis that benefits of increasing sire diversity contribute to selection for female extra-pair mating behaviour in P. ater was therefore not supported. [source]


    What maintains noncytoplasmic incompatibility inducing Wolbachia in their hosts: a case study from a natural Drosophila yakuba population

    JOURNAL OF EVOLUTIONARY BIOLOGY, Issue 2 2004
    S. Charlat
    Abstract Cytoplasmic incompatibility (CI) allows Wolbachia to invade hosts populations by specifically inducing sterility in crosses between infected males and uninfected females. In some species, non-CI inducing Wolbachia, that are thought to derive from CI-inducing ancestors, are common. In theory, the maintenance of such infections is not possible unless the bacterium is perfectly transmitted to offspring - and/or provides a fitness benefit to infected females. The present study aims to test this view by investigating a population of Drosophila yakuba from Gabon, West Africa. We did not find any evidence for CI using wild caught females. Infected females from the field transmitted the infection to 100% of their offspring. A positive effect on female fecundity was observed one generation after collecting, but this was not retrieved five generations later, using additional lines. Similarly, the presence of Wolbachia was found to affect mating behaviour, but the results of two experiments realized five generations apart were not consistent. Finally, Wolbachia was not found to affect sex ratio. Overall, our results would suggest that Wolbachia behaves like a neutral or nearly neutral trait in this species, and is maintained in the host by perfect maternal transmission. [source]


    Sexual conflict and indirect benefits

    JOURNAL OF EVOLUTIONARY BIOLOGY, Issue 5 2003
    E. Cameron
    Abstract Recent work on sexual selection and sexual conflict has explored the influence of indirect effects on the evolution of female mating behaviour. It has been suggested that the importance of these effects has been underestimated and that the influence of indirect effects may actually be of relatively greater significance than direct effects. Additionally, it has also been suggested that all indirect effects, both good genes and sexy son, are qualitatively equivalent. Here a counterpoint to these suggestions is offered. We argue two main points: (1) it is unlikely that indirect effects will commonly outweigh direct effects, and (2) that there are important differences between good genes and sexy son indirect effects that must be recognized. We suggest that acknowledgement of these distinctions will lead to increased understanding of processes operating in both sexual conflict and sexual selection. [source]


    Inbreeding depression and genetic load of sexually selected traits: how the guppy lost its spots

    JOURNAL OF EVOLUTIONARY BIOLOGY, Issue 2 2003
    C. Van Oosterhout
    Abstract To date, few studies have investigated the effects of inbreeding on sexually selected traits, although inbreeding depression on such traits can play an important role in the evolution and ecology of wild populations. Sexually selected traits such as ornamentation and courtship behaviour may not be primary fitness characters, but selection and dominance coefficients of their mutations will resemble those of traits under natural selection. Strong directional selection, for instance, through female mate-choice, purges all but the most recessive deleterious mutations, and the remaining dominance variation will result in inbreeding depression once populations undergo bottlenecks. We analysed the effects of inbreeding on sexually selected traits (colour pattern and courtship behaviour) in the male guppy, Poecilia reticulata, from Trinidad, and found a significant decline in the frequency of mating behaviour and colour spots. Such effects occurred although the genetic basis of these traits, many of which are Y-linked and hemizygous, would be expected to leave relatively little scope for inbreeding depression. Findings suggest that these sexually selected traits could reflect the genetic condition or health of males, and thus may be informative mate-cue characters for female choice as suggested by the ,good genes' model. [source]


    Behaviour and ecology of the western corn rootworm (Diabrotica virgifera virgifera LeConte)

    AGRICULTURAL AND FOREST ENTOMOLOGY, Issue 1 2009
    Joseph L. Spencer
    Abstract 1,The western corn rootworm (WCR) is a historic pest with a legacy of resistance and behavioural plasticity. Its behaviour and nutritional ecology are important to rootworm management. The success of the most effective and environmentally benign rootworm management method, annual crop rotation, was based on an understanding of rootworm behaviour and host,plant relationships. Enthusiastic adoption of crop rotation, provided excellent rootworm management, but also selected for behavioural resistance to this cultural control. 2,Though well-studied, significant gaps in WCR biology remain. Understanding the topics reviewed here (mating behaviour, nutritional ecology, larval and adult movement, oviposition, alternate host use, and chemical ecology) is a starting point for adapting integrated pest management and insect resistance management (IRM) to an expanding WCR threat. A presentation of significant questions and areas in need of further study follow each topic. 3,The expansion of WCR populations into Europe exposes this pest to new environmental and regulatory conditions that may influence its behaviour and ecology. Reviewing the state of current knowledge provides a starting point of reference for researchers and pest management decision-makers in North America and Europe. 4,The trend toward increasing adoption of transgenic maize will place an increasing premium on understanding WCR behaviour. IRM plans designed to promote sustainable deployment of transgenic hybrids are grounded on assumptions about WCR movement, mating and ovipositional behaviour. Preserving the utility of new and old management options will continue to depend on a thorough understanding of WCR biology, even as the ecological circumstances and geography of WCR problems become more complex. [source]


    Mating behaviour of the ,cosmopolitan' species Phyllognathopus viguieri (Copepoda: Harpacticoida) and its systematical significance

    JOURNAL OF ZOOLOGICAL SYSTEMATICS AND EVOLUTIONARY RESEARCH, Issue 4 2008
    D. Königshoff
    Abstract The mating behaviour was studied and recorded on video with individuals of four cultures of Phyllognathopus viguieri from different populations obtained from the interstitial water of a slow sand filter near the river Ruhr (Germany) (Ruhr population), from a compost heap in Bethesda (Maryland, USA) (Maryland population), from a rain gauge in Windsor Campbell farm (Jamaica) (Jamaica population), and a tree trunk with moss in a forest in the municipality of Rio de Janeiro (Brazil) (Brazil population). The mating behaviour was divided into the well-known initial phase, copula phase and postcopulatory mate guarding phase. An additional phase prior to the initial phase serves to recognize the female, the recognition phase. The mating behaviour is identical in the males of the Jamaica and Brazil populations of P. viguieri. A postcopulatory mate guarding phase is not found in these two groups. Here, we refute the hypothesis, that a postcopulatory mate guarding phase is found in taxa in which only adult males grasp adult females. The males of the Ruhr and Maryland populations differ from each other in their mating behaviour. Generally, the males of all four populations do not mate with fertilized females which are equally unattractive to the males, i.e., females mate only once in their lifetime to produce offspring. These results corroborate the view that the different populations of P. viguieri do not belong to a single cosmopolitan species. Zusammenfassung Das Kopulationsverhalten wurde an Vertretern aus vier Populationen von Phyllognathopus viguieri mit unterschiedlicher geographischer Herkunft mit Videoaufzeichnung untersucht. Die Tiere stammen aus dem Grundwasser der Ruhr (Langsamsandfilter) Deutschland (Ruhr-Population), aus Moospolstern im städtischen Wald von Rio de Janeiro, Brasilien (Brazil-Population), aus einem Komposthaufen in Bethesda, Maryland, USA (Maryland-Population) und aus einer Zisterne der Windsor Campbell farm, Jamaika (Jamaica-Population). Das Kopulationsverhalten kann in wie bereits bekannt Initialphase, Kopulaphase und Postkopulaphase eingeteilt werden. Während der Initialphase findet keine Balz statt. Als zusätzliche Phase findet vor der Initialphase eine Prüfphase statt, die dem Erkennen des Weibchens dient. Es konnte festgestellt werden, daß die Vertreter der vier Populationen sich in Bezug auf ihr Kopulationsverhalten voneinander unterscheiden. Das Kopulationsverhalten der Tiere aus Jamaika und Brasilien war identisch, sowohl die Dauer der einzelnen Phasen, als auch das Verhalten der einzelnen Versuchsindividuen. Bei ihnen trat keine Postkopulaphase auf. Bei den Tieren der Ruhr- und der Marylandpopulation trat eine Postkopulaphase von unterschiedlicher Dauer auf. Auch das Fortpflanzungsverhalten der Männchen war unterschiedlich. Die in der Literatur vertretene Hypothese, dass bei Taxa, in denen die Männchen nur adulte Weibchen greifen, eine Postkopulaphase vorkommt, wird in dieser Studie widerlegt. Die Weibchen kopulieren nur einmal in ihrem Leben, was für ihre gesamte Reproduktion ausreichend ist. Männchen kopulieren in der Regel nicht mit bereits begatteten Weibchen. Bereits begattete Weibchen zeigen ein Abwehrverhalten, um die Männchen an der Anheftung der Spermatophore zu hindern. Die Spermatophore wird ohne Hilfe der Schwimmbeine übertragen. Die Befestigung der Spermatophore am Genitalfeld des Weibchens geschieht mit einer Kittsubstanz, die vom Männchen abgegeben wird. Die Individuen der Ruhr- und der Marylandpopulation zeigen trotz einer bei beiden vorkommenden Postkopulaphase unterschiedliches Fortpflanzungsverhalten. Wir schließen daraus, dass sie unterschiedlichen biologischen Arten angehören. Die Individuen der Jamaika- und Brazil-Populationen sind einer Art zuzuordnen, die sich von diesen beiden Arten unterscheidet. Die in dieser Arbeit gemachten Beobachtungen sind eine Bestätigung dafür, dass P. viguieri keine kosmopolitische Art ist, sondern dass es sich tatsächlich um eine Gruppe kryptischer valider Arten handelt. [source]


    New results concerning the morphology of the most ancient dragonflies (Insecta: Odonatoptera) from the Namurian of Hagen-Vorhalle (Germany)

    JOURNAL OF ZOOLOGICAL SYSTEMATICS AND EVOLUTIONARY RESEARCH, Issue 4 2001
    G. Bechly
    The holotype specimen of the ,protodonate'Erasipteroides valentini (Brauckmann in Brauckmann et al., 1985) and the paratype specimen K-13 of the giant ,protodonate'Namurotypus sippeliBrauckmann and Zessin, 1989 from the Upper Carboniferous (Namurian B) of Hagen-Vorhalle (Germany) are redescribed, and a new specimen of Erasipteroides cf. valentini is described. The new evidence is used to refine the groundplan reconstruction of Odonatoptera and the reconstruction of odonatoid phylogeny. Prothoracic winglets for Erasipteroides and the absence of an archaedictyon are documented. Furthermore, a very long and sclerotized ovipositor with gonangulum is described from the female holotype specimen of Erasipteroides valentini, and it is proposed that it was not used for endophytic but for endosubstratic oviposition. The record of prothoracic winglets in early odonatoids, and their presence in fossil Palaeodictyoptera and ,protorthopteres', indicates that the groundplan of Pterygota indeed included three pairs of wings. A phylogenetic analysis suggests that the Palaeozoic giant Meganisoptera and "higher" odonatoids (incl. crowngroup Odonata) together form a monophyletic group which is here named Euodonatoptera. Erasipteroides and the other ,Erasipteridae' are shown to be more closely related to Euodonatoptera than to Eugeropteridae. The description of the male primary genital structures of Namurotypus sippeli is emended and a new interpretation is proposed, including new hypotheses concerning their function. The males of Namurotypus had a paired penis with a pair of lateral parameres, and a pair of leaf-like, but still segmented, gonopods. Segmented leg-like male gonopods are considered as a groundplan character of insects, while a paired penis is regarded as a putative synapomorphy of the palaeopterous insect orders Palaeodictyopteroida, Ephemeroptera, and Odonatoptera. It is proposed that Namurotypus did not mate by direct copulation but retained the archaic deposition of external spermatophores, just like the primarily wingless insects. The sigmoidal male cerci may have been placed behind the female head and used to drag the female over the spermatophore, which is remotely similar to the mating behaviour of some extant arachnids (e.g. Amblypygi). Three hypothetical scenarios regarding the evolution of secondary copulation in modern Odonata are proposed. Neue Erkenntnisse zur Morphologie der ältesten Libellen (Insecta: Odonatoptera) aus dem Namurium von Hagen-Vorhalle (Deutschland) Das Holotypusexemplar der ,Protodonate'Erasipteroides valentini (Brauckmann in Brauckmann et al., Geol. Paläont. Westfalen 3, 1,131, 1985) und das Paratypusexemplar K-13 der riesenwüchsigen ,Protodonate'Namurotypus sippeliBrauckmann and Zessin, 1989 aus dem Oberkarbon (Namurium B) von Hagen-Vorhalle (Deutschland) werden wiederbeschrieben. Die neuen Erkenntnisse werden zu einer Präzisierung der Grundplanrekonstruktion der Odonatoptera und für die Rekonstruktion der Libellenstammesgeschichte verwendet. Für Erasipteroides werden prothorakale Flügelchen beschrieben und das Fehlen eines Archaedictyons wird belegt. Des weiteren wird ein sehr langer und sklerotisierter Ovipositor mit Gonangulum für das weibliche Holotypusexemplar von Erasipteroides valentini beschrieben, und es wird vorgeschlagen, dass dieser nicht zur endophytischen Eiablage, sondern zur endosubstratischen Eiablage diente. Der Nachweis prothorakaler Flügelchen bei frühen Libellen sowie deren Vorkommen bei fossilen Palaeodictyoptera und ,Protorthopteren', deutet darauf hin, dass zum Grundplan der Pterygota drei Flügelpaare gehörten. Eine phylogenetische Analyse legt nahe, dass die riesenwüchsigen Meganisoptera des Paläozoikums und die ,höheren' Odonaten (inkl. Kronengruppe Odonata) gemeinsam eine monophyletische Gruppe bilden, die hier als Euodonatoptera benannt wird. Es wird gezeigt, dass Erasipteroides und die übrigen ,Erasipteridae' näher mit den Euodonatoptera verwandt sind als die Eugeropteridae. Die Beschreibung der primären männlichen Geschlechtsorgane von Namurotypus sippeli wird ergänzt, und eine neue Interpretation sowie neue Hypothesen zu deren Funktion werden vorgestellt. Die Männchen von Namurotypus besaßen einen paarigen Penis mit einem Paar lateraler Parameren und einem Paar blattartiger, aber noch segmentierter Gonopoden. Segmentierte, beinartige, männliche Gonopoden werden als Grundplanmerkmale der Insekten angesehen, während ein paariger Penis als potentielle Synapomorphie der paläopteren Insektenordnungen Palaeodictyopteroida, Ephemeroptera und Odonatoptera betrachtet wird. Es wird vorgeschlagen, dass die Paarung bei Namurotypus nicht durch eine direkte Kopulation ablief, sondern durch das Absetzen freier Spermatophoren, so wie bei den primär flügellosen Insekten. Die sigmoidalen männlichen Cerci könnten hinter dem weiblichen Kopf platziert worden sein, um das Weibchen über die Spermatophore zu dirigieren, ähnlich dem Paarungsverhalten mancher rezenter Spinnentiere (z.B. Amblypygi). Drei hypothetische Szenarien zur Evolution der sekundären Kopulation bei modernen Libellen werden vorgestellt. [source]


    Courtship and copulation, but not ejaculates, reduce the longevity of female field crickets (Gryllus bimaculatus)

    JOURNAL OF ZOOLOGY, Issue 4 2006
    P. W. Bateman
    Abstract Females of many taxa incur fitness costs from male sexual coercion and harassment leading to mating. Although male crickets cannot force copulations on females, female Gryllus bimaculatus in this study incurred significant reductions in longevity through being exposed to different levels of male courtship. Virgin females kept in isolation had the longest life spans. Reductions in longevity applied to females in sensory contact with males (without the opportunity to mate), females that courted and mated and females that mated but with fertilization being prevented. Females also incurred significant reductions in longevity when kept with other females, which may have been due to high levels of cannibalism. Consistent with previous studies, females appeared to incur no cost to longevity from receiving sperm or seminal fluid. It is known that female G. bimaculatus benefit genetically from multiple mating. However, this benefit could possibly be offset by the negative effect that male courtship and mating behaviour has on female longevity. [source]


    Destination-based seed dispersal homogenizes genetic structure of a tropical palm

    MOLECULAR ECOLOGY, Issue 8 2010
    JORDAN KARUBIAN
    Abstract As the dominant seed dispersal agents in many ecosystems, frugivorous animals profoundly impact gene movement and fine-scale genetic structure of plants. Most frugivores engage in some form of destination-based dispersal, in that they move seeds towards specific destinations, resulting in clumped distributions of seeds away from the source tree. Molecular analyses of dispersed seeds and seedlings suggest that destination-based dispersal may often yield clusters of maternal genotypes and lead to pronounced local genetic structure. The long-wattled umbrellabird Cephalopterus penduliger is a frugivorous bird whose lek mating system creates a species-specific pattern of seed dispersal that can potentially be distinguished from background dispersal processes. We used this system to test how destination-based dispersal by umbrellabirds into the lek affects gene movement and genetic structure of one of their preferred food sources Oenocarpus bataua, a canopy palm tree. Relative to background dispersal processes, umbrellabird mating behaviour yielded more diverse seed pools in leks that included on average five times more seed sources and a higher incidence of long-distance dispersal events. This resulted in markedly lower fine-scale spatial genetic structure among established seedlings in leks than background areas. These species-specific impacts of destination-based dispersal illustrate how detailed knowledge of disperser behaviour can elucidate the mechanistic link driving observed patterns of seed movement and genetic structure. [source]


    Cryptic behaviours, inverse genetic landscapes, and spatial avoidance of inbreeding in the Pacific jumping mouse

    MOLECULAR ECOLOGY, Issue 4 2007
    SACHA N. VIGNIERI
    Abstract Although the behaviour of individuals is known to impact the genetic make-up of a population, observed behavioural patterns do not always correspond to patterns of genetic structure. In particular, philopatric or dispersal-limited species often display lower-than-expected values of relatedness or inbreeding suggestive of the presence of cryptic migration, dispersal, or mating behaviours. I used a combination of microsatellite and mark,recapture data to test for the influence of such behaviours in a dispersal-limited species, the Pacific jumping mouse, within a semi-isolated population over three seasons. Despite short dispersal distances and a low rate of first generation migrants, heterozygosities were high and inbreeding values were low. Dispersal was male-biased; interestingly however, this pattern was only present when dispersal was considered to include movement away from paternal home range. Not unexpectedly, males were polygynous; notably, some females were also found to be polyandrous, selecting multiple neighbouring mates for their single annual litter. Patterns of genetic structure were consistent with these more inconspicuous behavioural patterns. Females were more closely related than males and isolation by distance was present only in females. Furthermore, detailed genetic landscapes revealed the existence of strong, significant negative correlations, with areas of low genetic distance among females overlapping spatially with areas of high genetic distance among males. These results support the hypothesis that the detected cryptic components of dispersal and mating behaviour are reducing the likelihood of inbreeding in this population through paternally driven spatial mixing of male genotypes and polyandry of females. [source]


    How female reed buntings benefit from extra-pair mating behaviour: testing hypotheses through patterns of paternity in sequential broods

    MOLECULAR ECOLOGY, Issue 9 2006
    KAREN M. BOUWMAN
    Abstract Extra-pair paternity is an important aspect of reproductive strategies in many species of birds. Given that in most species females control whether fertilization occurs, they are expected to benefit in some way from the extra-pair matings. In this study we use patterns of extra-pair paternity (EPP) in broods of individual reed buntings (Emberiza schoeniclus), both within and between seasons, to test four hypothesized female benefits: (1) assessing potential future partners and seeking (2) genetic diversity (3) good genes, or (4) compatible genes. Reed buntings are socially monogamous, multibrooded passerines with extremely high levels of extra-pair paternity. We studied a population of reed buntings in the Netherlands in 2002 and 2003; 51% of offspring in 74% of nests were extra-pair. We showed that patterns of EPP did not support the first and second hypotheses, since females did not form a pair with previous extra-pair partners, EPP was not evenly distributed among broods and more broods than expected were sired by a single male. Furthermore, there was no relation between a male's within- and extra-pair fertilization success, no consistency in EPP between breeding attempts, no effect of parental relatedness on EPP and several cases of reciprocal paternity. These patterns do not support the good genes hypothesis and are most consistent with the genetic compatibility hypothesis. However, our previous finding that older males are more successful in gaining EPP, suggests some effect of good genes. These hypotheses need not be mutually exclusive, as females may select compatible males above a certain quality threshold (e.g. old males). [source]


    Microsatellite analysis of female mating behaviour in lek-breeding sage grouse

    MOLECULAR ECOLOGY, Issue 8 2001
    K. Semple
    Abstract We used microsatellite DNA markers to genotype chicks in 10 broods of lek-breeding sage grouse, Centrocercus urophasianus, whose mothers' behaviour was studied by radio-tracking and observing leks. Previous behavioural studies suggested that almost all matings are performed by territorial males on leks and that multiple mating is rare. Two broods (20%) were sired by more than one male. Genetic analyses of the broods of eight females that visited an intensively studied lek were consistent with behavioural observations. Four females observed mating produced singly sired broods and males other than the individual observed copulating were excluded as sires for most or all of their chicks. Territorial males at the study lek were excluded as sires of broods of four other females that visited the lek but were not observed mating there. Radio-tracking suggested that two of these females mated at other leks. Our results confirm the reliability of mating observations at leks, but do not rule out a possible unseen component of the mating system. [source]


    Fragrances, male display and mating behaviour of Euglossa hemichlora: a flight cage experiment

    PHYSIOLOGICAL ENTOMOLOGY, Issue 4 2003
    Thomas Eltz
    Abstract., Male euglossine bees (Apidae: Euglossini) collect volatile substances (fragrances) from floral and nonfloral sources and store them in hair-filled cavities in their hind tibiae. Over time, males accumulate large quantities of complex and species-specific blends of fragrances. Various hypotheses have been put forward to explain this behaviour, including the idea that fragrance stores reflect the genetic quality of individual males and have evolved through sexual selection and female choice. Clear support of this hypothesis is lacking, largely because male,female interactions are both rare and difficult to observe in nature. Here, we report a flight cage experiment performed in Panama that permitted mating between virgin females (raised from brood cells) and males captured in the forest at fragrance baits. In the cage, eight individually marked males defended small territories around vertical perch sites and showed a characteristic display, which included a previously unreported ,leg-crossing' movement, possibly related to fragrance release. A total of six copulations and three copulatory attempts by Euglossa hemichlora were observed and partly recorded on video. The copulations, all of which were initiated by the female landing on a male perch, were short (4,10 s) and showed no signs of the transfer of chemical substances from male to female. In some cases, the male hovered directly over the female before descending to mount her, possibly facilitating fragrance evaluation by the female. After the experiment, the contents of the males' hind legs were analysed by gas chromatography-mass spectroscopy, which detected complex mixtures of terpenoids and aromatics (totalling 70 different compounds) dominated by hexahydrofarnesyl acetone, farnesene epoxide, ocimene and p -dimethoxy benzene. Individual total amounts of fragrances were neither related to display activity or perch occupancy by given males, nor to the frequency of matings achieved. Display activity was the only positive correlate of mating frequency. Generally, individuals had uniformly large amounts of stored fragrances in comparison to a previous study of three other species of Panamanian Euglossa. [source]


    Vascularization of the Fleshy Comb in the Domestic Chicken

    ANATOMIA, HISTOLOGIA, EMBRYOLOGIA, Issue 2005
    B. Vollmerhaus
    Up to now little is known about the vascularization of the chicken fleshy comb (crista carnosa). In order to evaluate the vascularization of the crista carnosa of the cook (breed White Leghorn), corrosion casts were created by injecting Plastoid into the internal carotid as described by Schummer (1951). Specimens were investigated by stereomicroscopy and scanning electron microscopy (SEM). Generally the dermis is highly vascularized by two capillary networks, which are localized beneath the epithelium and beneath the dermal papillas. The dense subepithelial network is characterized by the presence of sinusoid vessels. In the subcutaneous plexus numerous arteriovenous anastomoses of different types occur. Additionally there are arteriovenous anastomoses between the main vessels reaching the indentations of the comb. Our results show the presence of superficial and dense capillary networks and arteriovenous anastomoses are the anatomical basis for the functions of the chicken comb in mating behaviour and thermoregulation. Reference, Schummer, A. 1951: Simplified method for plastoid corrosion. Anat. Anaz. 98, 288,290. [source]


    Mating behaviour and alternative oviposition sites for male eggs in the heteronomous hyperparasitoid Coccophagus gurneyi Compere (Hymenoptera: Aphelinidae)

    AUSTRALIAN JOURNAL OF ENTOMOLOGY, Issue 1 2001
    GT Parkes
    Abstract The aphelinid parasitoid Coccophagus gurneyi Compere has unusual sex-related host relationships. Females are diploid and develop internally within mealybugs Pseudococcus calceolariae (Maskell). Males, in contrast, are haploid and hyperparasitic, developing on primary parasitoid larvae within the mealybugs. Furthermore, males have been claimed to be capable of either internal or external development, depending on the precise site of deposition of the haploid egg. This diversity of developmental pathways could indicate the existence of a sibling-species complex. We therefore quantified the mating and ovipositional behaviour of C. gurneyi, for comparison with that of an undescribed sibling species. We also checked whether the females deposit male eggs in alternative sites. The pattern of mating was found to be typical of mating behaviour in Coccophagus spp. and was consistent among all mating pairs, suggesting that the colony comprised one species. Further, the mating behaviour was significantly different from that of the undescribed sibling species. The site of male egg deposition varied and is apparently dictated by two factors; whether the mealybug is parasitised and, if so, the size of the parasitoid it contains. If the mealybugs were unparasitised or if the parasitoids within the mealybugs were small (< 0.53 mm), male eggs were deposited within the mealybug haemocoel. If the parasitoids were large (> 1.05 mm), male eggs were deposited within the parasitoids. These results support the claim of alternate host relationships and developmental pathways within males of C. gurneyi. [source]


    Behavioural correlates with hemipenis morphology in New World natricine snakes

    BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 1 2009
    RICHARD B. KING
    Copulatory organs (hemipenes) of male snakes vary markedly among species in shape and ornamentation. We suggest that sexual conflict over copulation duration may have shaped the evolution of hemipenis morphology, favouring more elaborate organs in species in which a long duration of copulation is especially beneficial to males, despite the associated costs to females. To test this proposition, we compare mating behaviour between two species of gartersnakes differing in hemipenis morphology. In addition, we review data on copulation duration and hemipenis morphology and relate hemipenis morphology to phylogeny among of New World natricines. As predicted, copulation duration was significantly shorter in the common gartersnake (Thamnophis sirtalis), a species with simple subcylindrical hemipenes, than in the plains gartersnake (Thamnophis radix), a species with more complex, bilobed organs. Furthermore, female T. radix frequently exhibited vigorous body rolls during copulation, a behaviour associated with copulation termination, whereas female T. sirtalis never exhibited this behaviour. Copulations were of shorter duration when female T. radix (but not T. sirtalis) more greatly exceeded males in body size, suggesting that females can more easily disengage from small males. Our review of New World natricines provides only weak evidence for an association between copulation duration and hemipenis morphology. Our mapping of hemipenis morphology onto the New World natricine phylogeny suggests that hemipenis morphology is evolutionarily plastic; both simple and bilobed hemipenes occur in all three major natricine clades, as well as in two of three gartersnake subclades and several sister-species pairs. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 98, 110,120. [source]


    Sex ratio, mating behaviour and Wolbachia infections in a sheetweb spider

    BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 1 2009
    BENGT GUNNARSSON
    The solitary sheetweb spider Pityohyphantes phrygianus has a female-biased primary sex ratio. Earlier studies have indicated that female post-copulatory position may influence the degree of bias, but the adaptive significance of the departure from a Fisherian 1 : 1 sex ratio is not known. In this study we show that there is a significant relationship between abdominal position and offspring sex ratio in undisturbed females. Moreover, female mating behaviour (and thus sex ratio) is correlated with female size, but this relationship may shift from negative to positive depending on the presence of the maternally acquired endosymbiotic bacterium Wolbachia in both sexes. A survey of wild-caught individuals shows that the incidence of Wolbachia infection in natural populations is high. This indicates that Wolbachia may be a significant factor influencing female post-copulatory behaviour and sex ratio in natural populations. We discuss various adaptive reasons for sex-ratio bias and behavioural plasticity in females. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 98, 181,186. [source]