Multiple mating and offspring quality in Lasius ants

Genetic diversity benefits for social insect colonies headed by polyandrous queens have received intense attention, whereas sexual selection remains little explored. Yet mates of the same queen may engage in sperm competition over the siring of offspring, and this could confer benefits on queens if the most successful sire in each colony (the majority sire) produces gynes (daughter queens) of higher quality. These benefits could be increased if high-quality sires make queens increase the percentage of eggs that they fertilize (unfertilized eggs develop into sons in social hymenopterans), or if daughters of better genetic quality are over-represented in the gyne versus worker class. Such effects would lead to female-biased sex ratios in colonies with high-quality majority gynes. I tested these ideas in field colonies of Lasius niger black garden ants, using body mass of gynes as a fitness trait as it is known to correlate with future fecundity. Also, I established the paternity of gynes through microsatellite DNA offspring analyses. Majority sires did not always produce heavier gynes in L. niger, but whenever they did do so colonies produced more females, numerically and in terms of the energetic investment in female versus male production. Better quality sires may be able to induce queens to fertilize more eggs or so-called caste shunting may occur wherever the daughters of better males are preferentially shunted to into the gyne caste. My study supports that integrating sexual selection and social evolutionary studies may bring a deeper understanding of mating system evolution in social insects.

Gene by environment interaction: effects of a single-gene and social-environment on reproductive phenotypes of fire ant queens

1. The gene Pgm-3 (or a closely linked gene) influences the phenotype and reproductive success of queens in multiple-queen (polygynous) colonies but not single-queen (monogynous) colonies of the Fire Ant Solenopsis invicta. 2. We investigated the mechanisms of differential phenotypic expression of Pgm-3 in these alternate social forms. Mature winged queens with the homozygous genotype Pgm-3(a/a) averaged 26% heavier than queens with the genotypes Pgm-3(a/b) and Pgm 3(b/b) in the polygynous form. Heterozygotes were slightly heavier (2%) than Pgm-3(b/b) queens in this form, demonstrating that the allele Pgm-3(a) is not completely recessive in its effects on weight. 3. There was no significant difference in weight among queens of the three Pgm-3 genotypes in the monogynous form, with the mean weight of monogynous queens slightly greater than that of polygynous Pgm-3(a/a) queens. Differences in weight between queens of the two social forms and among queens of the three genotypes in the polygynous form are not evident at the pupal stage and thus appear to develop during sexual maturation of the adults. This suggests that some component of the social environment of polygynous colonies inhibits weight gains during queen maturation and that Pgm-(3a/a) queens are relatively less sensitive to this factor. 4. To test whether the high cumulative queen pheromone level characteristic of polygynous colonies is the factor responsible for the differential queen maturation, we compared phenotypes of winged queens reared in split colonies in which pheromone levels were manipulated by adjusting queen number. Queens produced in colony fragments made monogynous were heavier than those produced in polygynous fragments, a finding consistent with the hypothesis that pheromone level affects the reproductive development of queens. However, genotype-specific differences in weights of queens were similar between the two treatments, suggesting that pheromone level was not the key factor of the social environment responsible for the gene-environment interaction. 5. To test whether limited food availability to winged queens associated with the high brood/worker ratios in polygynous colonies is the factor responsible for this interaction, similar split-colony experiments were performed. Elevated brood/worker ratios decreased the weight of winged queens but there was no evidence that this treatment intensified differential weight gains among queens with different Pgm-3 genotypes. Manipulation of the amount of food provided to colonies had no effect on queen weight. 6. The combined data indicate that cumulative pheromone level and brood/worker ratio are two of the factors responsible for the differences in reproductive phenotypes between monogynous and polygynous winged queens but that these factors are not directly responsible for inducing the phenotypic effects of Pgm-3 in polygynous colonies.

Neutral and selection-driven decay of sexual traits in asexual stick insects.

Environmental shifts and lifestyle changes may result in formerly adaptive traits becoming non-functional or maladaptive. The subsequent decay of such traits highlights the importance of natural selection for adaptations, yet its causes have rarely been investigated. To study the fate of formerly adaptive traits after lifestyle changes, we evaluated sexual traits in five independently derived asexual lineages, including traits that are specific to males and therefore not exposed to selection. At least four of the asexual lineages retained the capacity to produce males that display normal courtship behaviours and are able to fertilize eggs of females from related sexual species. The maintenance of male traits may stem from pleiotropy, or from these traits only regressing via drift, which may require millions of years to generate phenotypic effects. By contrast, we found parallel decay of sexual traits in females. Asexual females produced altered airborne and contact signals, had modified sperm storage organs, and lost the ability to fertilize their eggs, impeding reversals to sexual reproduction. Female sexual traits were decayed even in recently derived asexuals, suggesting that trait changes following the evolution of asexuality, when they occur, proceed rapidly and are driven by selective processes rather than drift.

Predicting the mating system from phenotypic correlations between life-history and sperm quality traits in the Alpine whitefish Coregonus zugensis

The mating behavior and reproductive strategies of Alpine whitefish like Coregonus zugensis (Nusslin) are poorly understood, probably because they spawn in deep water where direct observations are difficult. In this study, we interpret life-history and sperm quality traits of fish that we caught from their spawning place. We found that males invest heavily into gonadal tissue (up to 5.6% of their body weight), which is, in comparison to other fish, consistent with external fertilization, distinct pairing and moderate to high communal spawning, or no pairing and low to moderate communal spawning. Sperm competition theory and recent experimental studies on other salmonids predict that males optimize ejaculate characteristics in relation to the costs of sperm and the level of competition they have to expect: dominant males are predicted to invest less into ejaculate quality and to have slower spermatozoa than subdominant males. We found that spermatozoa of older males are slower than those of younger males. Moreover, older males have larger breeding tubercles, a secondary sexual trait that has, in some previous studies, been found to be linked to good condition and to good genetic quality. Our results suggest that C. zugensis has age-linked reproductive strategies, that multimale spawning is common, i.e., that sperm competition plays a significant role, and that older males are on average dominant over younger males at the spawning place.

Ecological niche overlap in sister species: how do oil-collecting bees Macropis europaea and M. fulvipes (Hymenoptera: Melittidae) avoid competition and hybridization?

Oil-collecting bees are found worldwide and always in association with particular oil-producing flowers. In the Western Palearctic, three oil-collecting bee species within the genus Macropis (Hymenoptera, Melittidae) interact in a tight pollination mutualism with species of the only European oil-producing plant genus Lysimachia L. (Myrsinaceae). Two of these oil-collecting bees (Macropis europaea and Macropis fulvipes) show overlapping geographic distributions, comparable morphologies, and similar ecological characteristics (e.g., habitat type, floral preferences). In view of these similarities, we presume that hybridization should occur between the two species unless potential variation among the species' ecological niches prevents it, simultaneously decreasing competition for resources. Using modern genetic analyses and ecological niche modeling on a large bee sampling throughout Europe, we discuss new perspectives on the ecology and evolutionary history of this mutualism.

Flight energetics in relation to sexual differences in the mating behaviour of a mayfly, Siphlonurus aestivalis

Mayflies (Ephemeroptera) are known to have short adult life-spans. Adults are unable to feed, and they utilize reserves stored during their aquatic larval stage. Energy reserves (fat, glycogen, and free sugars) of mature larvae, subimagoes and imagoes of both sexes of Siphlonurus aestivalis Eaton were compared. All the stages of both sexes had low glycogen and free sugar contents, and the only significant change occurred during the transformation of the mature larva to subimago when almost all the reserves of free sugars were used up. Glycogen and free sugars may serve as energy sources permitting individuals to swim and fly out of the water during emergence. Fat made up most of the energy reserves of mature larvae and was the main source of energy used during the final development of both sexes. Young adult males had high fat reserves which they used as a source of energy for their swarming flights. In contrast, females did not seem to use a significant amount of fat for flight. This difference is probably related to the different mating strategies of the sexes in this species. Males perform long flights waiting for females, whereas females perform only brief flights to mate and reproduce.

Prevalence and dimensions of sexual orientation in Swiss adolescents: a cross-sectional survey of 16 to 20-year-old students.

AIM: Sexual orientation plays an important part in building identity during adolescence. The aim of this study was to describe patterns of sexual orientation, including sexual attraction, fantasies, affiliations and behaviour. METHODS: The study was based on the analysis of data from computerized self-administered questionnaires of a Swiss national survey on the sexual life of 16 to 20-year-old adolescents (n = 2,075 girls and 2,208 boys.). RESULTS: Overall, 95.0% of girls and 96.2% of boys described themselves as predominantly heterosexual; 1.4% of girls and 1.7% of boys as predominantly homosexual or bisexual; and 2.8% of teenagers (girls: 3.6%; boys: 2.1%) were "unsure" of their sexual orientation. The reported prevalence of homosexual attraction (girls: 2.0%; boys: 2.9%) exceeded homosexual fantasies (girls: 0.4%; boys: 0.5%) and affiliations (girls: 0.3%; boys: 0.5%). Among the 4205 respondents, 31 girls (1.5% of girls) and 56 boys (2.5% of boys) reported sexual behaviour (experience or penetrative intercourse) with a person of the same sex. Among 1.5% of girls and 2.5% of boys who reported sexual behaviour with a person of the same sex, 65% of boys and 80% of girls nevertheless considered themselves as heterosexual. CONCLUSION: For a comprehensive understanding of sexual orientation in adolescence a differentiated look at dimensions of sexual orientation is indispensable. This applies to clinical settings, public health and research.

The Effect of Sexual Abuse on Children's Attachment Representations in Chile.

Child sexual abuse is associated with problems in children's emotional development, particularly increased insecurity of attachment. However, few studies have examined its effect on the organization of attachment representations in preschoolers, and the findings of those that have been conducted have not been entirely consistent. Therefore, this study aims to analyze the effect of child sexual abuse on attachment representation quality in a sample of children 3 to 7 years old in Chile. The results indicate child sexual abuse does affect children's attachment representation quality. The attachment narratives of child sexual abuse victims scored significantly higher than nonvictims on the hyperactivity and disorganization dimensions of attachment. These results are discussed in terms of attachment theory, clinical findings on child sexual abuse, and clinical implications.

Clustering of HCV coinfections on HIV phylogeny indicates domestic and sexual transmission of HCV.

BACKGROUND: HCV coinfection remains a major cause of morbidity and mortality among HIV-infected individuals and its incidence has increased dramatically in HIV-infected men who have sex with men(MSM). METHODS: Hepatitis C virus (HCV) coinfection in the Swiss HIV Cohort Study(SHCS) was studied by combining clinical data with HIV-1 pol-sequences from the SHCS Drug Resistance Database(DRDB). We inferred maximum-likelihood phylogenetic trees, determined Swiss HIV-transmission pairs as monophyletic patient pairs, and then considered the distribution of HCV on those pairs. RESULTS: Among the 9748 patients in the SHCS-DRDB with known HCV status, 2768(28%) were HCV-positive. Focusing on subtype B(7644 patients), we identified 1555 potential HIV-1 transmission pairs. There, we found that, even after controlling for transmission group, calendar year, age and sex, the odds for an HCV coinfection were increased by an odds ratio (OR) of 3.2 [95% confidence interval (CI) 2.2, 4.7) if a patient clustered with another HCV-positive case. This strong association persisted if transmission groups of intravenous drug users (IDUs), MSMs and heterosexuals (HETs) were considered separately(in all cases OR>2). Finally we found that HCV incidence was increased by a hazard ratio of 2.1 (1.1, 3.8) for individuals paired with an HCV-positive partner. CONCLUSIONS: Patients whose HIV virus is closely related to the HIV virus of HIV/HCV-coinfected patients have a higher risk for carrying or acquiring HCV themselves. This indicates the occurrence of domestic and sexual HCV transmission and allows the identification of patients with a high HCV-infection risk.

Habitat fragmentation, ecology and sexual selection in forest bird species in Monteverde, Costa Rica

Abstract Forest fragmentation is often associated with local extinction and changes in species abundance patterns. The main topic of this thesis is the effect of forest fragmentation on birds in Monteverde, Costa Rica. This thesis also studies aspects of sexual selection and ecology of Long-tailed Manakins, Chiroxiphia Linearis. Chapter 1 investigates bird species assemblages in two degrees of forest fragmentation. It is shown that the distribution, abundance and diversity of forest bird species are strongly influenced by the amount of forest in the landscape matrix. Presence of cattle within the forest influences the presence of some bird species. The prevalence and intensity of ticks and blood parasites on birds in relation to fragmentation is described in Chapter 2. Overall tick prevalence is 3%. Understory birds are significantly more infested with ticks than species at intermediate heights. Tick prevalence on birds does not differ significantly between two degrees of forest fragmentation and individual tick loads tend to be higher in High- than in Low-fragmentation sites. Infestations by the blood parasites Haemoproteus sp. was low except in white-eared ground sparrow, Melozone leucotis, that is 28% and is significantly higher in High- than in Low-fragmentation sites. In chapter 3 results on the ecology and habitat movements of the Bare-necked Umbrellabird, Cephalopterus glabricollis, are presented. The abundance of umbrellabirds at high elevations during the breeding season coincides with the highest peak of fruit abundance. Birds leave the protected area during the non-breeding season moving to unprotected forest fragments. In chapter 4 ontogenetic changes in feather morphology through sexual maturity in Long-tailed Manakins are described. In adult males, rectrices length is positively correlated to testis volume. Changes in male morphology during ontogeny in the long-tailed manakin appear to be associated with their specific-display behaviours. Significant interpopulation differences in the morphology of Long-tailed Manakins are shown in chapter 5. These differences are more accentuated in morphological traits related to flight displays. A field experiment demonstrates that long rectrices impose flying costs for males and females. A reduction in flying ability was found to be strongest in males from a population presenting the highest degree of sexual dimorphism. Résumé La fragmentation des forêts est souvent associée avec des modifications dans l'abondance des espèces et des extinctions locales. Le thème principale de cette thèse est l'étude de l'effet de la fragmentation des forêts sur les oiseaux de Monteverde, Costa Rica. Elle décrit par ailleurs certains aspects de la sélection sexuelle et l'écologie du manakin à longue queue, Chiroxiphia linearis. Dans le Chapitre 1 je montre que la distribution, l'abondance et la diversité des assemblages d'oiseaux vivant dans la forêt sont fortement influencées pas le degré de fragmentation de celle ci. Par ailleurs, la présence ou l'absence de bétail dans les forêts influence la présence de certaines espèces d'oiseaux. Dans le chapitre 2 j'ai étudié la prévalence et l'intensité d'infestation par des tiques ainsi que la présence de parasites sanguins chez les oiseaux en relation avec la fragmentation des forêts. La prévalence globale de tiques est de 3 %, les oiseaux vivant au niveau du sol étaient plus souvent infectés par des tiques que les espèces se déplaçant à un niveau plus élevé. La prévalence de tiques sur les oiseaux n'était pas significativement différente entre les paysages avec différentes fragmentations. Les parasites sanguins du genre Haemoproteus sp. étaient présents à très basse fréquence à l'exception chez Melozone leucotis ou la prevalence était de 28% et significativement plus élevée chez les oiseaux vivant dans les forêts à forte fragmentation. Dans le Chapitre 3 je présente des résultats sur l'écologie et les mouvements entre habitats chez le "Bare-necked umbrellabird", Cephalopterus glabricollis. Cette espèce endémique du Costa Rica niche à haute altitude durant la période d'abondance des fruits et réalise une migration altitudinale vers des zones basses durant la saison de non reproduction. Dans le chapitre 4 je présente les changements ontogénétiques dans la morphologie du plumage des manakins à longue queue. Chez les mâles, les changements de morphologie semblent être associés avec leurs comportements de parade spécifiques. Dans le chapitre 5 je présente des différences morphologiques significative entre deux populations chez le manakin à longue queue et je montre que la capacité de vols chez les mâles est plus fortement influencée dans la population avec le degré de dimorphisme sexuel le plus prononcé.

Male mutation bias and possible long-term effects of human activities.

The ability of a population to adapt to changing environments depends critically on the amount and kind of genetic variability it possesses. Mutations are an important source of new genetic variability and may lead to new adaptations, especially if the population size is large. Mutation rates are extremely variable between and within species, and males usually have higher mutation rates as a result of elevated rates of male germ cell division. This male bias affects the overall mutation rate. We examined the factors that influence male mutation bias, and focused on the effects of classical life-history parameters, such as the average age at reproduction and elevated rates of sperm production in response to sexual selection and sperm competition. We argue that human-induced changes in age at reproduction or in sexual selection will affect male mutation biases and hence overall mutation rates. Depending on the effective population size, these changes are likely to influence the long-term persistence of a population.

The Evolution of Sexual Dysfunction in Young Men Aged 18-25 Years

PURPOSE: To assess the evolution of sexual dysfunctions among young males after an average of 15 months follow-up to determine the predictive factors for this evolution and the characteristics differentiating young males who continue reporting a sexual dysfunction from those who do not. METHODS: We conducted a prospective cohort study in two Swiss military recruitment centers mandatory for all Swiss national males aged 18-25 years. A total of 3,700 sexually active young males filled out a questionnaire at baseline (T0) and follow-up (T1: 15.5 months later). Main outcome measures were self-reported premature ejaculation (PE) and erectile dysfunction (ED). RESULTS: Overall, 43.9% of young males who reported (PE) and 51% of those reporting (ED) at T0 still reported it at T1. Moreover, 9.7% developed a PE problem and 14.4% developed an ED problem between T0 and T1. Poor mental health, depression, and consumption of medication without prescription were predictive factors for PE and ED. Poor physical health, alcohol consumption, and less sexual experience were predictive factors for PE. ED persistence was associated with having multiple sexual partners. CONCLUSIONS: This is the first longitudinal study to examine sexual dysfunctions among young males. Our results show high prevalence rates among young males for maintaining or developing a sexual dysfunction over time. Consequently, when consulting with young males, health professionals should inquire about sexual dysfunctions as part of their routine psychosocial assessment and leave the subject open for discussion. Future research should examine in more detail the relationship between sexual dysfunctions and poor mental health.