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High levels of extra-pair paternity in an isolated, low-density, island population of tree swallows (Tachycineta bicolor).

Molecular genetic studies have suggested that apparently nonbreeding males ('floaters') may account for a significant proportion of extra-pair paternity (EPP) in avian populations. Attempts to determine the influence of breeding density on EPP are therefore confounded by the presence of a subpopulation of floaters whose numbers are difficult to estimate. To study EPP in a tree swallow (Tachycineta bicolor) population with few floaters, we chose a nestbox grid on an island with an excess of available breeding sites and very few floaters. We obtained DNA samples from 13 complete families and performed DNA profiling on them using four microsatellite loci. For comparison, we also obtained a sample of 58 extra-pair young (EPY) from a mainland population typed at five microsatellite loci. Paternity assignments among resident males in both populations were made using the microsatellite profiles and a likelihood-based statistical method. Of the 67 island nestlings typed, we found 37 (55%) nestlings from 11 (85%) different nests that were EPY. The proportion of nestlings that were EPY and the proportion of broods containing EPY did not differ significantly between island and mainland populations studied previously. There was no significant difference between island and mainland populations in the proportion of extra-pair paternities assigned among neighbouring resident males. Male breeding density does not appear to affect the ability of female tree swallows to obtain extra-pair fertilizations, at least over the range of densities studied so far. The rate of EPP has remained remarkably consistent over many years, studies and populations implying an important role of active female choice in determining EPP.

Animals↗

Sex-biased dispersal and a density-independent mating system in the Australian brushtail possum, as revealed by minisatellite DNA profiling.

Natal dispersal can have important effects on mammal population structure and dynamics following a local population crash. Such dispersal is of practical importance when applied to the control of pest species because dispersal may significantly, and undesirably, reduce the population recovery time following a control operation. The relative dispersal rate of the sexes is also critical because that too will affect the rate of population increase. Here, we describe a field experiment in which we reduce the density of two populations of the Australian brushtail possum, and use genetic similarity, as estimated by minisatellite DNA profiles, to investigate dispersal in the original (undisturbed) and recovering populations. Our results show that the genetic similarity within the undisturbed populations was lower between males than between females. Conversely, the genetic similarities between males and females in the two recovering populations were not significantly different, while relatedness among males was significantly higher in the recovering populations when compared with those in the pre-removal populations. These data indicate two important characteristics of dispersal in possums: (i) that dispersal in established populations is sex biased towards males; and (ii) that within the first 3 years following population control, 'the vacuum effect', whereby individuals from areas adjacent to a control area expand their home range and invade the depopulated area, is the most important factor in the re-colonization process for possums. We found no evidence that the mating system, which is polygynous, varied when the density was markedly reduced. These results indicate that drastic reductions in population density by conventional control will not affect the rate of spread of biological control agents that rely on sexual transmission for dissemination.

Animals↗

Sperm length influences fertilization success during sperm competition in the snail Viviparus ater.

Sperm form and size is tremendously variable within and across species. However, a general explanation for this variation is lacking. It has been suggested that sperm size may influence sperm competition, and there is evidence for this in some taxa but not others. In addition to normal fertilizing sperm, a number of molluscs and insects produce nonfertile sperm that are also extremely morphologically variable, and distinct from fertilizing forms. There is evidence that nonfertile sperm play an indirect role in sperm competition by decreasing female remating propensity in Lepidopterans, but in most taxa the function of parasperm is unknown. We investigated the role of nonfertile (oligopyrene) sperm during sperm competition in the fresh water snail Viviparus ater. Previous studies found that the proportion of oligopyrene sperm increased with the risk of sperm competition, and hence it seems likely that these sperm influence fertilization success during competitive matings. In mating experiments in which females were sequentially housed with males, we examined a range of male characteristics which potentially influence fertilization success. We found that the size of oligopyrene sperm was the best predictor of fertilization success, with males having the longer sperm siring the highest proportion of offspring. Furthermore, we found a positive shell size and sperm concentration effect on paternity, and females with multiply sired families produced more offspring than females mating with only one male. This result suggests polyandry is beneficial for female snails.

Analysis of Variance↗

Marijuana use among the adolescent children of high-risk drug-abusing fathers.

This study examines marijuana use among children of male drug abusers. Subjects were 83 African-American and European-American male drug abusers, of whom the majority were injection drug users, and their children. Thirty-one of the fathers were HIV-positive and 52 were HIV-negative. Using logistic regression analyses, we explored cross-sectionally the relationship between four psychosocial domains (ie, paternal attributes, adolescent problem behaviors, father-adolescent relations, and environment) and adolescent marijuana use. The father's use of illegal drugs and his failure to cope adaptively predicted adolescent marijuana use, while a close father-child bond predicted less adolescent marijuana use. Adolescent problem behaviors predicted an increased likelihood of marijuana use. Furthermore, hierarchical regression analysis demonstrated that the adolescent's problem behavior mediated the associations between both the father-adolescent relationship and environmental factors with adolescent marijuana use. Reducing the risk factors and enhancing the protective factors within each of the domains could help reduce marijuana use among the adolescent children of drug-abusing fathers. Moreover, if a father is a drug abuser, it is important to help him establish a close bond with his child in order to help attenuate the influence of his drug use on the child's marijuana use.

Adaptation, Psychological↗

The Y chromosome of Drosophila melanogaster exhibits chromosome-wide imprinting.

Genomic imprinting is well known as a regulatory property of a few specific chromosomal regions and leads to differential behavior of maternally and paternally inherited alleles. We surveyed the activity of two reporter genes in 23 independent P-element insertions on the heterochromatic Y chromosome of Drosophila melanogaster and found that all but one location showed differential expression of one or both genes according to the parental source of the chromosome. In contrast, genes inserted in autosomal heterochromatin generally did not show imprint-regulated expression. The imprints were established on Y-linked transgenes inserted into many different sequences and locations. We conclude that genomic imprinting affecting gene expression is a general property of the Drosophila Y chromosome and distinguishes the Y from the autosomal complement.

Animals↗

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.

Animals↗

Does multiple paternity improve fitness of the frog Crinia georgiana?

In the Australian myobatrachid frog Crinia georgiana simultaneous polyandry occurs in about half of all matings, which leads to multiple paternity, but reduced fertilization success and occasional female mortality. Multiple paternity may provide benefits to females that compensate for these costs, for example, through enhanced genetic diversity of a clutch. In nature, embryos and tadpoles of C. georgiana develop in shallow, temporary pools and may be exposed to fluctuating water levels and the risk of desiccation between rain events. Fertilization by genetically diverse sires may act as a bet hedge against these conditions. To evaluate this hypothesis, females were artificially mated with one or two males in the field and eggs and larvae reared in the laboratory under constant or fluctuating developmental conditions. Experiment 1 exposed embryos from single- and multiple-paternity clutches to conditions where eggs were completely covered during development or eggs sat in air on a moist substrate. Experiment 2 exposed freshly hatched larvae from single- and multiple-paternity clutches to constant wet conditions, where larvae were completely covered, or fluctuating wet conditions, where larvae ranged from being completely submersed to partially exposed over a 13-day cycle. We measured mean performance and best performance as alternate measures of genetic benefits. There were no effects of paternity on percent survival to hatching, time to hatching, body size at hatching, percent survival to metamorphosis, time to metamorphosis, or body size at metamorphosis. We also analyzed variance within clutches as a measure of genetic diversity. Again there were no predictable effects of multiple paternity. Polyandry does not appear to provide any genetic benefits that compensate for the high costs of polyandry in this species.

Animals↗

Multiple paternity in the red-eyed treefrog Agalychnis callidryas (Cope).

DNA fingerprinting of tadpoles from two different 'one female-two male' matings of the red-eyed treefrog, Agalychnis callidryas, revealed multiple paternity of offspring. Offspring were assigned paternity based on bands shared with the putative father, but not shared between putative fathers or with the mother. Paternity was split approximately 44/56% and 36/64% in two matings. These results do not support a hypothesis of sperm priority in access to unfertilized eggs by primary males. Multiple paternity may be commonplace in species of anurans with matings by multiple males.

Animals↗

Men's desire for children carrying their genes and sexual jealousy: a test of paternity uncertainty as an explanation of male sexual jealousy.

In a classic study, Buss, Larson, Westen, and Semmelroth found that men were more distressed by the thought of a partner's sexual infidelity (labeled sexual jealousy) and women were more distressed by the thought of a partner's emotional infidelity (labeled emotional jealousy). Buss and his associates explained the results by suggesting that men are concerned about uncertainty of paternity, that is, the possibility of raising another man's child while believing that the child is their own. To test this explanation, the Desire for Children Scale was created. Its internal consistency and test-retest reliabilities were .86 and .89, respectively. Scores correlate with stated Number of Children Desired (convergent validity) but none of the Big-Five traits (divergent validity). It was hypothesized that for men scores on this scale would correlate positively with scores on sexual jealousy. The Desire for Children Scale and the two Sexual vs Emotional Jealousy items of Buss and his associates were given to 49 men and 55 women college students enrolled in psychology courses. Their average age was 19.9 yr. (SD= 3.7), and average year in school was 2.0 (SD= 1.2). Subjects volunteered to participate in the study in exchange for course credit. The hypothesis was confirmed and gives support to the uncertainty of paternity explanation.

Adult↗

Establishing a link between cultural evolution and sexually transmitted diseases.

It is argued that archaic sexually transmitted diseases influenced cultural traditions by reducing multiple sexual partners within communities. In this article, the adverse consequences of current sexually transmitted diseases are surveyed: Such infections decrease fertility of women and increase infant mortality; those adverse consequences are especially potent when antibiotics are not readily available. Cultural (cross-generational transmission of learned) responses to the threat of widespread infertility and elevated infant mortality rates are hypothesized to include the implementation of expectations for restricted numbers of sexual partners. These expectations, formal or informal, have been instituted within the context of biological predispositions, the "certainty of paternity" model, already-established traditions, and the need for a social father to be aligned with the mother-child dyad. A case study of the contemporary United States is offered as a heuristic example of how and why cultural choices may be developed and sustained.

Cultural Evolution↗

Child bereavement after paternal suicide.

BACKGROUND: Studies of child suicide survivors are rare and often these studies have not included direct interviews with children. OBJECTIVES: To describe the bereavement process in a sample of prepubertal children whose fathers died by suicide within the previous three years. METHODS: Sixteen prepubertal children, their mothers, and a relative or caretaker were interviewed to examine grief, trauma, and behavior within 25 months of paternal suicide. RESULTS: Reminiscing was the most frequently endorsed grief behavior. Males were more likely than females to score above the standard means for CBCL scores. PTSD scores were significantly related to parental threats of divorce and exposure to death by discovery of the body. CONCLUSIONS: The concept of grief and trauma as separate and overlapping phenomena is supported by the study findings.

Bereavement↗

Hypothalamic vasopressin gene expression increases in both males and females postpartum in a biparental rodent.

In previous studies, the closely related neuropeptide hormones oxytocin and vasopressin have been implicated in the central mediation of parental behaviour. Several studies in rats and sheep have demonstrated a role for oxytocin in the initiation of maternal behaviour. Recently, a few studies in a biparental species, the prairie vole (Microxytocinus ochrogaster) have suggested that vasopressin is important for paternal care. The present study investigated this latter possibility by measuring changes in vasopressin and oxytocin hypothalamic gene expression 1 day and 6 days following parturition in prairie voles which show paternal care and in montane voles (M. montanus) which lack paternal care. In prairie voles, vasopressin gene expression increased in both males and females postpartum, relative to sexually naive controls. In the non-paternal montane vole, no change in vasopressin gene expression was observed in either sex. In contrast to this species difference in vasopressin gene expression, hypothalamic oxytocin gene expression increased in both prairie and montane vole females, but not in males of either species. To augment measures of gene expression, we assessed vasopressin (V1a) and oxytocin receptor binding in both species. Although forebrain vasopressin V1a receptor binding was not altered following parturition in either species, oxytocin receptor binding increased in the ventromedial nucleus of the hypothalamus in females, but not males, in both prairie and montane voles. In summary, vasopressin gene expression increases in both males and females postpartum in a biparental species and oxytocin gene expression and receptor binding increase selectively in females. These results are consistent with earlier reports of a role for vasopressin in paternal care and for oxytocin in maternal behaviour.

Animals↗

Behavioral and neurochemical alterations in the offspring of rats after maternal or paternal inhalation exposure to the industrial solvent 2-methoxyethanol.

The industrial solvent 2-methoxyethanol (2ME) has antifertility effects in male rats at 300 ppm and is teratogenic in rats and rabbits at 50 ppm. The present research investigated if exposure of paternal or maternal animals to 25 ppm 2ME, the current U.S. permissible occupational exposure limit, would produce detectable effects in the offspring. Eighteen male young-adult Sprague-Dawley rats were exposed to 25 ppm 2ME 7 hr/day, 7 days/week for 6 weeks; they were then mated with untreated females which were allowed to deliver and rear their young. In addition, groups of 15 pregnant rats were exposed 7 hr/day on gestation days 7-13 or 14-20 and allowed to deliver and rear their young. At birth, litters were culled to 4 females and 4 males for behavioral testing of neuromotor function, activity, and simple learning ability on days 10 through 90. In addition, brains from newborn and 21-day-old offspring were analyzed for neurochemical deviations from controls. No effects on paternal or maternal animals, nor on the number or weight of live offspring, were noted. Behavioral testing revealed significant differences from controls only in avoidance conditioning of offspring of mothers exposed on days 7-13. In contrast, neurochemical deviations were observed in brains from 21-day-old offspring from the paternally exposed group as well as from both maternally exposed groups; changes were numerous in the brainstem and cerebrum but were fewer in the cerebellum and midbrain. Thus it appears that both paternal and maternal inhalation of 25 ppm 2ME produces some effect which is reflected in neurochemical deviations in the offspring.

Acetylcholine↗