The consequences of facultative sex in a prey adapting to predation

A species reproductive mode, along with its associated costs and benefits, can play a significant role in its evolution and survival. Facultative sexuality, being able to reproduce both sexually and asexually, has been deemed evolutionary favourable as the benefits of either mode may be fully realized. In fact, many studies have focused on identifying the benefits of sex and/or the forces selecting for increased rates of sex using facultative sexual species. The costs of either mode, however, can also have a profound impact on a population's evolutionary trajectory. Here, we used experimental evolution and fitness assays to investigate the consequences of facultative sexuality in prey adapting to predation. Specifically, we compared the adaptive response of algal prey populations exposed to constant rotifer predation and which had alternating cycles of asexual and sexual reproduction where sexual episodes were either facultative (sexual and asexual progeny simultaneously propagated) or obligate (only sexual progeny propagated). We found that prey populations with facultative sexual episodes reached a lower final relative fitness and suffered a greater trade‐off in traits under selection, that is defence and competitive ability, as compared to prey populations with obligate sexual episodes. Our results suggest that costs associated with sexual reproduction (germination time) and asexual reproduction (selection interference) were amplified in the facultative sexual prey populations, leading to a reduction in the net advantage of sexuality. Additionally, we found evidence that the cost of sex was reduced in the obligate sexual prey populations because increased selection for sex was observed via the spontaneous production of sexual cells. These results show that certain costs associated with facultative sexuality can affect an organism's evolutionary trajectory.     

Androgenic hormones and aging--the link with female sexual function

In women, sexual function, hormones and aging are inextricably related. Sexual activity in women involves interest and motivation, the ability to become aroused and achieve orgasm, the pleasure of the experience and subsequent personal satisfaction. Androgens, as endogenous hormones or given as a therapy, potentially influence female sexual function, with research into the effects of exogenous androgens in women mostly devoted to effects on sexual desire. Some studies have been conducted to delineate the effects of testosterone on arousal, however arousal determined by laboratory measures does not always correlate with subjective reporting of a sensation of arousal. Overall large randomised controlled trials of exogenous testosterone show benefits over placebo on sexual desire, arousal, orgasm, pleasure and satisfaction. The aspects of consideration of androgen therapy for women that continue to stimulate debate in this therapeutic area include whether female sexual dysfunction is a condition that merits pharmacotherapy, how effective is such treatment and whether testosterone therapy is safe.     

Imperfect Genes, Fisherian Mutation and the Evolution of Sex

In this paper we present a mathematical model of mutation and selection that allows for the coexistence of multiple alleles at a locus with very small selective differences between alleles. The model also allows for the determination of fitness by multiple loci. Models of this sort are biologically plausible. However, some previous attempts to construct similar models have assumed that all mutations produce a decrease in fitness, and this has led to a tendency for the average fitness of population members to decline when population numbers are finite. In our model we incorporate some of the ideas of R. A. FISHER, so that both deleterious and beneficial mutations are possible. As a result, average fitness tends to approach a stationary distribution. We have used computer simulation methods to apply the Fisherian mutation model to the problem of the evolution of sex and recombination. The results suggest that sex and recombination can provide very large benefits in terms of average fitness. The results also suggest that obligately sexual species will win ecological competitions with species that produce a substantial fraction of their offspring asexually, so long as the number of sites under selection within the genomes of the competing species is not too small and the population sizes are not too large. Our model focuses on fertility selection in an hermaphroditic plant. However, the results are likely to generalize to a wide variety of other situations as well.     

Relations de pouvoir et égalitarisme sexuel chez un groupe d'étudiants marocains

In order to verify what are the differences in the field of power relations, equality in the sphere of sexual roles as well as the control of sexual drives among young Moroccans, 111 university students (50 men and 61 women) have answered an anonymous self-administred questionnaire dealing with their sexual lives. Statistical results show that for both sexes, sexuality appears more as a sharing experience than a power one. Both sexes consider also that it is the prerogative of men to initiate sexual relations as well to decide the use of condom. Men consider that they are more able to express their sexual demands than women. The latter are more in control of their sexual drives and of the modulation of their sexual life. The results indicate also the presence of a sexual double standard with men being more sexually active than women. These data confirm on the whole the qualitative data provided by anthropological research on sexuality in Morocco.     

The evolutionary ecology of pre- and post-meiotic sperm senescence

Male reproductive success is an extremely variable fitness component. Understanding the maintenance of this variation is a key challenge in evolutionary biology. An often neglected source of variation in male reproductive success is determined by age-dependent patterns of decline in sperm fitness. Two pathways mediate sperm senescence: pre-meiotic senescence of somatic and germ cells of the ageing male, and post-meiotic ageing of the spermatozoon. Recently, theoretical and empirical studies have highlighted wide-ranging implications of both pathways. We clarify different mechanisms of sperm senescence, outlining their distinct evolutionary implications for the male, the female and the zygote, and their influence on fundamental evolutionary processes, including the evolution of anisogamy, sexual conflict, sexual selection, and applied issues such as assisted conception.     

Evaluation of sexual functions and sexual behaviors after penile brachytherapy in men treated for penile carcinoma

Purpose

To assess sexual functions and behaviors of men treated by penile brachytherapy for a cancer of the penis.

Materials and methods

Thirty eight men (19 patients treated by penile brachytherapy for a cancer of the penis and 19 age paired-matched controls) participated in a survey about sexuality. The mean age of patients and controls were 73.2 +/- 11.7 and 70.0 +/- 10.5 years, respectively (NS). Controls were men without penile pathology, without history of cancer and no evidence of cognitive impairment. All agreed to participate in the survey about sexuality using 2 questionnaires : the IIEF questionnaire, which explores 4 domains of sexual functions, namely erection, satisfaction, orgasm and desire, and a questionnaire created using the BASIC IDEA grid, which addresses nine domains: behavior, affect, sensation, self-image, cognition, interpersonal, drugs, expectation and attitude.

Results

Patients had better scores than controls in 3 domains of the IIEF: erection, desire and satisfaction. These results contrasted with the frequency of intercourse and the quality of erection (evaluated through the BASIC IDEA questionnaire) that were not significantly different between the two populations. Patients also had significantly higher frequency of masturbation (p <0.001) lower worry about sexual performance and higher expected satisfaction for future life (p: 0.021) than controls.

Conclusion

Penile brachytherapy is a treatment of cancer of the penis that seems to have a moderated impact on sexual functions since most of sexual scores are not inferior in these patients than in age pair-matched controls.

     

Fitness consequences of hybridization between ecotypes of Avena barbata: hybrid breakdown, hybrid vigor, and transgressive segregation

Hybridization is an important factor in the evolution of plants; however, many of the studies that have examined hybrid fitness have been concerned with the study of early generation hybrids. We examined the early- and late-generation fitness consequences of hybridization between two ecotypes of the selfing annual Avena barbata in a greenhouse environment as well as in two natural environments. Fitness of early generation (F2) hybrids reflects both the action of dominance effects (hybrid vigor) and recombination (hybrid breakdown) and was not significantly different from that of the midparent in any environment. Fitness of later generation (F6) recombinant inbred lines (RILS) derived from the cross reflect both the loss of early generation heterozygosity as well as disruption of any coadapted gene complexes present in the parents. In all environments, F6 RILs were on average significantly less fit than the (equally homozygous) midparent, indicating hybrid breakdown through the disruption of epistatic interactions. However, the inbred F6 were also less fit than the heterozygous F2, indicating that hybrid vigor also occurs in A. barbata, and counteracts hybrid breakdown in early generation hybrids. Also, although the F6 generation mean is lower than the midparent mean, there are individual genotypes within the F6 generation that are capable of outperforming the parental ecotypes in the greenhouse. Fewer hybrid genotypes are capable of outperforming the parental ecotypes in the field. Overall, these experiments demonstrate how a single hybridization event can result in a number of outcomes including hybrid vigor, hybrid breakdown, and transgressive segregation, which interact to determine long-term hybrid fitness.     

Assessing the extent of genome-wide intralocus sexual conflict via experimentally enforced gender-limited selection

Intralocus sexual conflict, which occurs when a trait is selected in opposite directions in the two sexes, is a taxonomically widespread phenomenon. The strongest genetic evidence for a gender load due to intralocus sexual conflict comes from the Drosophila melanogaster laboratory model system, in which a negative genetic correlation between male and female lifetime fitness has been observed. Here, using a D. melanogaster model system, we utilize a novel modification of the 'middle class neighbourhood' design to relax selection in one sex, while maintaining selection in the other. After 26 generations of asymmetrical selection, we observed the expected drop in fitness of the non-selected sex compared to that of the selected sex, consistent with previous studies of intralocus sexual conflict in this species. However, the fitness of the selected sex also dropped compared to the base population. The overall decline in fitness of both the selected and the unselected sex indicates that most new mutations are harmful to both sexes, causing recurrent mutation to build a positive genetic correlation for fitness between the sexes. However, the steeper decay in the fitness of the unselected sex indicates that a substantial number of mutations are gender-limited in expression or sexually antagonistic. Our experiment cannot definitively resolve these two possibilities, but we use recent genomic data and results from previous studies to argue that sexually antagonistic alleles are the more likely explanation.     

Multigenerational effects of inbreeding in Cucurbita pepo ssp. texana (Cucurbitaceae)

The shape of the fitness function relating the decline in fitness with coefficient of inbreeding (f) can provide evidence concerning the genetic basis of inbreeding depression, but few studies have examined inbreeding depression across a range of f using noncultivated species. Futhermore, studies have rarely examined the effects of inbreeding depression in the maternal parent on offspring fitness. To estimate the shape of the fitness function, we examined the relationship between f and fitness across a range off from 0.000 to 0.875 for components of both male and female fitness in Cucurbita pepo ssp. texana. Each measure of female fitness declined with f, including pistillate flower number, fruit number, seed number per fruit, seed mass per fruit, and percentage seed germination. Several aspects of male fitness also declined with f, including staminate flower number, pollen number per flower, and the number of days of flowering, although cumulative inbreeding depression was less severe for male (0.34) than for female function (0.39). Fitness tended to decline linearly with f between f = 0.00 and f = 0.75 for most traits and across cumulative lifetime fitness (mean = 0.66), suggesting that individual genes causing inbreeding depression are additive and the result of many alleles of small effect. However, most traits also showed a small reduction in inbreeding depression between f = 0.75 and f = 0.875, and evidence of purging or diminishing epistasis was found for in vitro pollen-tube growth rate. To examine inbreeding depression as a maternal effect, we performed outcross pollinations on f = 0.0 and f = 0.5 mothers and found that depression due to maternal inbreeding was 0.07, compared to 0.10 for offspring produced through one generation of selfing. In at least some families, maternal inbreeding reduced fruit number, seed number and mass, staminate flower number, pollen diameter, and pollen-tube growth rate. Collectively these results suggest that, while the fitness function appears to be largely linear for most traits, maternal effects may compound the effects of inbreeding depression in multigenerational studies, though this may be partially offset by purging or diminishing epistasis.     

Biological fitness of Trichoderma atroviride during long-term storage,after production in different culture conditions

Identification of the production and storage factors that affect conidium germination and bioactivity (fitness) will assist the success of biological control agents. Effects of culturing conditions on conidium fitness of Trichoderma atroviride LU132 were examined in different storage conditions over time. Abiotic factors (temperature, nutrients, water activity and pH) during production were studied. Conidia from the culturing regimes which resulted in greatest and least bioactivity against Rhizoctonia solani in dual culture were selected to assess effects of storage conditions on conidium fitness. Fitness of the test conidia was examined after storage at 30°C and at 0% or 50% relative humidity (RH) over 6 months. Fitness declined over time, and the decline was greater for 50% RH than 0% RH, probably through reduced metabolic activity of conidia during long-term storage. Stored conidia were probably affected by dehydration, temperature and other factors such as oxidation, before and during storage, and also by rehydration after storage. The greatest number of conidia and germination percentage resulted from production at 25°C, but greatest bioactivity resulted from those produced at 30°C. No significant effects on bioactivity were detected between the conidium production treatments C?:?N 5?:?1 and C?:?N 160?:?1, indicating that C?:?N ratio in culture medium is not important for conidium survival of T. atroviride.     

Density-dependent habitat selection: Testing the theory with fitness data

Summary According to density-dependent habitat selection theory, reproductive success should decline with increased density. Fitness should be similar between habitats if habitat selection follows an ideal free distribution; fitness should be dissimilar between habitats if habitat selection is modified by territorial behavior. I tested these assumptions by examining a variety of fitness estimates obtained from white-footed mice living in nest boxes in forest, forest edge and fencerow habitats in southwestern Ontario. As expected, mean litter size declined with increased population density. Litter sizes, adult longevity and the proportion of adult animals in breeding condition were not significantly different among the three habitats. The success at recruiting at least one offspring to the adult population and the number of recruits per litter were much greater in the forest than in either of the other two habitats. Fitness was thus unequal among habitats and the results confirm both assumptions of density-dependent habitat selection theory for territorial white-footed mice.     

Health Risks in Same-Sex Attracted Ugandan University Students: Evidence from Two Cross-Sectional Studies

Widespread discrimination across much of sub-Saharan Africa against persons with same-sex sexuality, including recent attempts in Uganda to extend criminal sanctions against same-sex behavior, are likely to have profound effects on this group’s health, health care access, and well-being. Yet knowledge of the prevalence of same-sex sexuality in this region is scarce. This study aimed to systematically examine prevalence of same-sex sexuality and related health risks in young Ugandan adults. We conducted two cross-sectional survey studies in south-western Uganda targeting student samples (n = 980, n = 1954) representing 80% and 72% of the entire undergraduate classes attending a university in 2005 and 2010, respectively. A questionnaire assessed items concerning same-sex sexuality (same-sex attraction/fantasies, same-sex sexual relations), mental health, substance use, experience of violence, risky sexual behavior, and sexual health counseling needs. Our findings showed that same-sex sexual attraction/fantasies and behavior were common among male and female students, with 10–25% reporting having sexual attraction/fantasies regarding persons of the same-sex, and 6–16% reporting same-sex sexual relations. Experiences of same-sex sexuality were associated with health risks, e.g. poor mental health (2010, AOR = 1.5; 95% CI: 1.0–2.3), sexual coercion (2010, AOR 2.9; CI: 1.9–4.6), and unmet sexual health counseling needs (2010, AOR 2.2; CI: 1.4–3.3). This first study of young adults in Uganda with same-sex sexuality found high levels of health needs but poor access to health care. Effective response is likely to require major shifts in current policy, efforts to reduce stigmatization, and reorientation of health services to better meet the needs of this vulnerable group of young people.     

Sexual Conflict,Life Span,and Aging

The potential for sexual conflict to influence the evolution of life span and aging has been recognized for more than a decade, and recent work also suggests that variation in life span and aging can influence sexually antagonistic coevolution. However, empirical exploration of these ideas is only beginning. Here, we provide an overview of the ideas and evidence linking inter- and intralocus sexual conflicts with life span and aging. We aim to clarify the conceptual basis of this research program, examine the current state of knowledge, and suggest key questions for further investigation.Sexual conflict arises because the sexes maximize their fitness via different, and often mutually incompatible, strategies, and its signature has been detected across a wide range of morphological, physiological, behavioral, and life-history traits in many species. A number of investigators have suggested that sexual conflict could play an important role in the evolution of two particularly interesting life-history traits: life span and aging (Svensson and Sheldon 1998; Promislow 2003; Bonduriansky et al. 2008; Maklakov and Lummaa 2013). Sexual conflict can affect life span and aging rate at both proximate (within-generation) and ultimate (evolutionary) scales. Sexually antagonistic behavioral or physiological interactions that increase mortality rate in one or both sexes (interlocus sexual conflict) could drive the evolution of faster life histories. Moreover, sex-specific optimization of reproductive strategies may often result in sex differences in life span and aging rates, and sexually antagonistic selection on shared genetic architecture can displace one or both sexes from their sex-specific optima for these traits (intralocus sexual conflict). Conversely, a change in life histories because of environmental fluctuations could affect the degree of sexual conflict in a population and influence sexual coevolution. Although evidence for sexual conflict is rapidly accumulating, our understanding of its relationship to life span and aging remains rudimentary. In this review, we provide a critical review of recent literature and highlight areas that require further investigation.     

Partitioning of resources: the evolutionary genetics of sexual conflict over resource acquisition and allocation

Fitness depends on both the resources that individuals acquire and the allocation of those resources to traits that influence survival and reproduction. Optimal resource allocation differs between females and males as a consequence of their fundamentally different reproductive strategies. However, because most traits have a common genetic basis between the sexes, conflicting selection between the sexes over resource allocation can constrain the evolution of optimal allocation within each sex, and generate trade‐offs for fitness between them (i.e. ‘sexual antagonism’ or ‘intralocus sexual conflict’). The theory of resource acquisition and allocation provides an influential framework for linking genetic variation in acquisition and allocation to empirical evidence of trade‐offs between distinct life‐history traits. However, these models have not considered the emergence of trade‐offs within the context of sexual dimorphism, where they are expected to be particularly common. Here, we extend acquisition–allocation theory and develop a quantitative genetic framework for predicting genetically based trade‐offs between life‐history traits within sexes and between female and male fitness. Our models demonstrate that empirically measurable evidence of sexually antagonistic fitness variation should depend upon three interacting factors that may vary between populations: (1) the genetic variances and between‐sex covariances for resource acquisition and allocation traits, (2) condition‐dependent expression of resource allocation traits and (3) sex differences in selection on the allocation of resource to different fitness components.     

Aging and primate male sexual behavior

Old male rhesus macaques display less sexual behavior than young and middle-aged males. The decrease in sexual activity occurs without a statistically significant decline in gonadal hormones or change in diurnal patterns of serum T, DHT, or LH. Levels of sexual activity are not increased by administering T to old intact males. However, the hormone is effective in increasing sexual behavior in old long-term-castrated males. Performance can be increased to levels observed in equally old untreated intact males. Readily detectable physical disabilities of old age have been observed to impair sexual performance, but the observed general decline in sexual activity cannot be accounted for by known physical disabilities. Novelty, as represented by a change in female partner or by a change in environment, has not increased sexual performance in old rhesus males. Only when old males were paired with empirically selected preferred females is their sexual behavior increased to levels displayed by young males. Drugs reported to increase levels of sexual behavior in rats have thus far been less effective in old rhesus males than powdered rhinoceros horn has been in man. The probable absence of a placebo effect in rhesus males should increase their usefulness as an animal model for the study of sexual behavior in aging men.     

Loss of oestrus, concealed ovulation and paternity confusion in free-ranging Hanuman langurs.

Ovarian cycles in catarrhine primates are uniquely characterized by prolonged periods of sexual activity in which the timings of ovulation and copulation do not necessarily correspond. According to current hypotheses of primate social evolution, extended sexuality in multi-male groups might represent part of a female strategy to confuse paternity in order to reduce the risk of infanticide by males. We test this hypothesis by examining mating behaviour in relation to timing of ovulation and paternity outcome in a multi-male group of free-living Hanuman langurs. Using faecal progestogen measurements, we first document that female langurs have extended receptive periods in which the timing of ovulation is highly variable. Next, we demonstrate the capacity for paternity confusion by showing that ovulation is concealed from males and that copulations progressively decline throughout the receptive phase. Finally, we demonstrate multiple paternity, and show that despite a high degree of monopolization of receptive females by the dominant male, non-dominant males father a substantial proportion of offspring. We believe that this is the first direct evidence that extended periods of sexual activity in catarrhine primates may have evolved as a female strategy to confuse paternity.     

Secular trends in self reported sexual activity and satisfaction in Swedish 70 year olds: cross sectional survey of four populations, 1971-2001

Objective To study secular trends in self reported sexual behaviour among 70 year olds.Design Cross sectional survey.Settings Four samples representative of the general population in Gothenburg, Sweden.Participants 1506 adults (946 women, 560 men) examined in 1971-2, 1976-7, 1992-3, and 2000-1.Main outcome measures Sexual intercourse, attitudes to sexuality in later life, sexual dysfunctions, and marital satisfaction.Results From 1971 to 2000 the proportion of 70 year olds reporting sexual intercourse increased among all groups: married men from 52% to 68% (P=0.002), married women from 38% to 56% (P=0.001), unmarried men from 30% to 54% (P=0.016), and unmarried women from 0.8% to 12% (P<0.001). Men and women from later birth cohorts reported higher satisfaction with sexuality, fewer sexual dysfunctions, and more positive attitudes to sexuality in later life than those from earlier birth cohorts. A larger proportion of men (57% v 40%, P<0.001) and women (52% v 35%, P<0.001) reported very happy relationships in 2000-1 compared with those in 1971-2. Sexual debut before age 20 increased in both sexes: in men from 52% to 77% (P<0.001) and in women from 19% to 64% (P<0.001).Conclusion Self reported quantity and quality of sexual experiences among Swedish 70 year olds has improved over a 30 year period.     

Age specificity of inbreeding load in Drosophila melanogaster and implications for the evolution of late-life mortality plateaus

Current evolutionary theories explain the origin of aging as a byproduct of the decline in the force of natural selection with age. These theories seem inconsistent with the well-documented occurrence of late-life mortality plateaus, since under traditional evolutionary models mortality rates should increase monotonically after sexual maturity. However, the equilibrium frequencies of deleterious alleles affecting late life are lower than predicted under traditional models, and thus evolutionary models can accommodate mortality plateaus if deleterious alleles are allowed to have effects spanning a range of neighboring age classes. Here we test the degree of age specificity of segregating alleles affecting fitness in Drosophila melanogaster. We assessed age specificity by measuring the homozygous fitness effects of segregating alleles across the adult life span and calculated genetic correlations of these effects across age classes. For both males and females, we found that allelic effects are age specific with effects extending over 1-2 weeks across all age classes, consistent with modified mutation-accumulation theory. These results indicate that a modified mutation-accumulation theory can both explain the origin of senescence and predict late-life mortality plateaus.     

Hormones, sexuality and fertility in women

The extent to which the sexuality of women shows a predictable menstrual cyclicity varies considerably from woman to woman, though the most common times for peaks of sexual interest are the pre- and post-menstrual weeks, not the middle of the cycle. Evidence is presented suggesting that mood is an important determinant of the post-menstrual peak of sexuality, whereas the pre-menstrual peak may depend on other mechanisms such as a delayed effect of the mid-cycle rise in testosterone.
Generally, the evidence for a relationship between hormones and sexual behaviour is much more variable and inconsistent in women than in men. Various explanations for this difference have been proposed, including a greater genetic variability of hormone-behaviour relationships in women. Evidence, relevant to this hypothesis, of a relationship between frequency of sexual activity and the fertility of the ovarian cycle is reviewed and alternative explanations for the findings are considered.