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1.
Parental food provisioning and offspring begging influence each other reciprocally. This makes both traits agents and targets of selection, which may ultimately lead to co‐adaptation. The latter may reflect co‐adapted parent and offspring genotypes or could be due to maternal effects. Maternal effects are in turn likely to facilitate in particular mother‐offspring co‐adaptation, further emphasized by the possibility that mothers are sometimes found to be more responsive to offspring need. However, parents may not only differ in their sensitivity, but often play different roles in postnatal care. This potentially impinges on the access to information about offspring need. We here manipulated the information on offspring need as perceived by parents by playing back begging calls at a constant frequency in the nest‐box of blue tits (Cyanistes caeruleus). We measured the parental response in provisioning to our treatment, paying particular attention to sex differences in parental roles and whether such differences alter the perception of the intensity of our manipulation. This enabled us to investigate whether an information asymmetry about offspring need exists between parents and how such an asymmetry relates to co‐adaptation between parental provisioning and offspring begging. Our results show that parents indeed differed in the frequency how often they perceived the playback due to the fact that females spent more time with their offspring in the nest box. Correcting for the effective exposure of an adult to the playback, the parental response in provisioning covaried more strongly (positive) with offspring begging intensity, independent of the parental sex, indicating coadaptation on the phenotypic level. Females were not more sensitive to experimentally increased offspring need than males, but they were exposed to more broadcasted begging calls. Therefore, sex differences in access to information about offspring need, due to different parental roles, have the potential to impinge on family conflicts and their resolution.  相似文献   

2.
It is hypothesized from within an evolutionary framework that females should be less invested in peer relations than males. Investment was operationalized as enjoyment in Study 1 and as preference for interaction in Study 2. In the first study, four- and six-year-old children’s enjoyment of peer interaction was observed in 26 groups of same-sex peers. Girls were rated as enjoying their interactions significantly less than boys. In the second study, six- and nine-year-old children were interviewed about the individuals with whom they spend time in their homes and neighborhoods and about the individuals who participate in their favorite activities. The proportion of individuals named by children who were peers was significantly lower for girls than boys both in children’s neighborhoods and in children’s favorite activities. Results strongly support the hypothesis that females and males have evolved differential preferences for interaction with peers.  相似文献   

3.
Abstract

Spatial visualization scores were obtained on the members of two hundred families. Large sex differences favoring males were found in both parents and offspring. Familial correlations, however, did not order themselves as predicted from the theory that human spatial visualization is under the control of an X‐linked recessive gene. The results are compatible with a sex limitation and/or socialization theory of ability acquisition.  相似文献   

4.
Marijuana is the most widely used illicit drug in the U.S., and marijuana use by women is on the rise. Women have been found to be more susceptible to the development of cannabinoid abuse and dependence, have more severe withdrawal symptoms, and are more likely to relapse than men. The majority of research in humans suggests that women are more likely to be affected by cannabinoids than men, with reports of enhanced and decreased performance on various tasks. In rodents, females are more sensitive than males to effects of cannabinoids on tests of antinociception, motor activity, and reinforcing efficacy. Studies on effects of cannabinoid exposure during adolescence in both humans and rodents suggest that female adolescents are more likely than male adolescents to be deleteriously affected by cannabinoids. Sex differences in response to cannabinoids appear to be due to activational and perhaps organizational effects of gonadal hormones, with estradiol identified as the hormone that contributes most to the sexually dimorphic effects of cannabinoids in adults. Many, but not all sexually dimorphic effects of exogenous cannabinoids can be attributed to a sexually dimorphic endocannabinoid system in rodents, although the same has not yet been established firmly for humans. A greater understanding of the mechanisms underlying sexually dimorphic effects of cannabinoids will facilitate development of sex-specific approaches to treat marijuana dependence and to use cannabinoid-based medications therapeutically.  相似文献   

5.
Consistent sex differences in foraging trip duration, feeding locality and diet of breeding Adélie penguins (Pygoscelis adeliae) were demonstrated at two widely separated locations over several breeding seasons. Differences in foraging behaviour were most pronounced during the guard stage of chick rearing. Female penguins made on average longer foraging trips than males, ranged greater distances more frequently and consumed larger quantities of krill. In contrast, males made shorter journeys to closer foraging grounds during the guard period and fed more extensively on fish throughout chick rearing. Mean guard stage foraging trip durations over four seasons at Béchervaise Island, Eastern Antarctica and over two seasons at Edmonson Point, Ross Sea ranged between 31 and 73 h for females and 25 and 36 h for males. Ninety percent of males tracked from Béchervaise Island by satellite during the first 3 weeks post-hatch foraged within 20 km of the colony, while the majority (60%) of females travelled to the edge of the continental shelf (80–120 km from the colony) to feed during this period. Received: 10 December 1997 / Accepted: 10 April 1998  相似文献   

6.
Journal of Plant Research - Causes of secondary sexual dimorphism (SSD) in dioecious plants are very poorly understood, especially in woody plants. SSD is shown mainly in mature plants, but little...  相似文献   

7.
Parent-offspring conflict may arise because the lifetime reproductive success of the parent is more influenced by its life span than by reproductive success during a particular reproductive event, while the fitness of an offspring depends firstly on its own survival as a juvenile and only subsequently on its own reproductive success. The naive immune system of young animals may allow offspring to be much more affected by parasites than their parents, and thus cause an initial asymmetry in a potential parent-offspring conflict. We investigated this type of conflict by assessing the health status and the immune response of parent and offspring sand martins Riparia riparia infested with manipulated loads of ticks Ixodes lividus (nests either treated with pyrethrin, water, or just visited). The prevalence and the intensity of tick infestations differed among treatments, with low tick loads in nests with the pyrethrin treatment. Ticks reduced the reproductive success of the host and increased offspring wing length. Broods with ticks had higher leukocyte concentrations and concentrations of immunoglobulins. The concentration of immunoglobulins in nestlings was negatively related to brood size and nestling tarsus length. Nestlings receiving the control treatments had a positive association between wing length and the concentration of immunoglobulins and a negative association between tarsus length and immunoglobulins. In contrast, adult sand martins did not respond to the parasite treatment in terms of immune response. Hence, the naive immune system of nestlings may be the crucial factor causing the parent-offspring conflict over costs of parasitism to be resolved to the advantage of parents that may sacrifice nestlings in heavily parasitized nests. Received: 30 March 1998 / Accepted: 5 December 1998  相似文献   

8.
9.
The renal vasopressin V(2) receptor (V(2)R) plays a critical role in physiological and pathophysiological processes associated with arginine vasopressin (AVP)-induced antidiuresis. Because clinical data suggests that females may be more prone to hyponatremia from AVP-mediated antidiuresis, we investigated whether there are sex differences in the expression and function of the renal V(2)R. In normal Sprague-Dawley rat kidneys, V(2)R mRNA and protein expression was 2.6- and 1.7-fold higher, respectively, in females compared with males. To investigate the potential physiological implications of this sex difference, we studied changes in urine osmolality induced by the AVP V(2)R agonist desmopressin. In response to different doses of desmopressin, there was a graded increase in urine osmolality and decrease in urine volume during a 24-h infusion. Females showed greater mean increases in urine osmolality and greater mean decreases in urine volume at 0.5 and 5.0 ng/h infusion rates. We also studied renal escape from antidiuresis produced by water loading in rats infused with desmopressin (5.0 ng/h). After 5 days of water loading, urine osmolality of both female and male rats escaped to the same degree physiologically, but V(2)R mRNA and protein in female kidneys was reduced to a greater degree (-63% and -73%, respectively) than in males (-32% and -48%, respectively). By the end of the 5-day escape period, renal V(2)R mRNA and protein expression were reduced to the same relative levels in males and females, thereby abolishing the sex differences in V(2)R expression seen in the basal state. Our results demonstrate that female rats express significantly more V(2)R mRNA and protein in kidneys than males, and that this results physiologically in a greater sensitivity to V(2)R agonist administration. The potential pathophysiological implications of these results are that females may be more susceptible to the development of dilutional hyponatremia because of a greater sensitivity to endogenously secreted AVP.  相似文献   

10.
Three-year-old children were observed in two free-play sessions and participated in a toy-retrieval task, in which only one of six tools could be used to retrieve an out-of-reach toy. Boys engaged in more object-oriented play than girls and were more likely to use tools to retrieve the toy during the baseline tool-use task. All children who did not retrieve the toy during the baseline trials did so after being given a hint, and performance on a transfer-of-training tool-use task approached ceiling levels. This suggests that the sex difference in tool use observed during the baseline phase does not reflect a difference in competency, but rather a sex difference in motivation to interact with objects. Amount of time boys, but not girls, spent in object-oriented play during the free-play sessions predicted performance on the tool-use task. The findings are interpreted in terms of evolutionary theory, consistent with the idea that boys’ and girls’ play styles evolved to prepare them for adult life in traditional environments.  相似文献   

11.
Women have more body fat than men, but in contrast to the deleterious metabolic consequences of the central obesity typical of men, the pear-shaped body fat distribution of many women is associated with lower cardiometabolic risk. To understand the mechanisms regulating adiposity and adipose tissue distribution in men and women, significant research attention has focused on comparing adipocyte morphological and metabolic properties, as well as the capacity of preadipocytes derived from different depots for proliferation and differentiation. Available evidence points to possible intrinsic, cell autonomous differences in preadipocytes and adipocytes, as well as modulatory roles for sex steroids, the microenvironment within each adipose tissue, and developmental factors. Gluteal-femoral adipose tissues of women may simply provide a safe lipid reservoir for excess energy, or they may directly regulate systemic metabolism via release of metabolic products or adipokines. We provide a brief overview of the relationship of fat distribution to metabolic health in men and women, and then focus on mechanisms underlying sex differences in adipose tissue biology.  相似文献   

12.
To understand the impact of alternative translation initiation on a proteome, we performed a proteome‐wide study on protein turnover using positional proteomics and ribosome profiling to distinguish between N‐terminal proteoforms of individual genes. By combining pulsed SILAC with N‐terminal COFRADIC, we monitored the stability of 1,941 human N‐terminal proteoforms, including 147 N‐terminal proteoform pairs that originate from alternative translation initiation, alternative splicing or incomplete processing of the initiator methionine. N‐terminally truncated proteoforms were less abundant than canonical proteoforms and often displayed altered stabilities, likely attributed to individual protein characteristics, including intrinsic disorder, but independent of N‐terminal amino acid identity or truncation length. We discovered that the removal of initiator methionine by methionine aminopeptidases reduced the stability of processed proteoforms, while susceptibility for N‐terminal acetylation did not seem to influence protein turnover rates. Taken together, our findings reveal differences in protein stability between N‐terminal proteoforms and point to a role for alternative translation initiation and co‐translational initiator methionine removal, next to alternative splicing, in the overall regulation of proteome homeostasis.  相似文献   

13.
Capsule Some males brought building materials to nests and females who were paired with such males laid heavier clutches.  相似文献   

14.
In most mammals, juvenile males tend to be more vulnerable to starvation than females and consequently experience a higher mortality. This has been attributed to selection on high male growth rates in response to strong intrasexual competition. Among primates, by contrast, it has been noted that females tend to be less viable as juveniles. This has been attributed to a greater ability of juvenile males to contest for food. An alternative explanation is that there is local resource competition, and adults of the resident sex (usually females) attempt to limit the recruitment of unrelated immatures of the same sex by harassing them. These ideas are not mutually exclusive. A set of predictions from these three hypotheses was derived for two social systems and two levels of food supply. They were tested using estimates of juvenile mortality and juvenile sex ratios of non-human primates based on over 40 data sets drawn from the literature. The results indicate that the local resource competition hypothesis provides the best explanation for the observed patterns in differential juvenile mortality in primates. The contrast between the findings for primates and those for other taxa is attributed to the low growth rate of immatures and the widespread occurrence of conditions conducive to local resource competition in primates.  相似文献   

15.
Males often have reduced immune function compared to females but the proximate mechanisms underlying this taxonomically widespread pattern are unclear. Because immune function is resource-dependent and sexes may have different nutritional requirements, we hypothesized that sexual dimorphism in immune function may arise from differential nutrient intake (acquisition hypothesis). To test this hypothesis, we examined patterns of phenoloxidase (PO) activity in relation to nutrient consumption in Queensland fruit flies (Q-flies). In the first experiment, flies were allowed to choose their preferred nutrient intake. Compared with males, female Q-flies had higher PO activity, consumed more calories, and preferred a higher protein:carbohydrate (P:C) diet, suggesting that differential acquisition could explain sex differences. In the second experiment, we restricted flies to one of 12 diets varying in protein and carbohydrate concentrations and mapped PO activity for each sex onto a nutritional landscape. Counter to our hypothesis, females had higher PO activity than males at any given level of nutrient intake. Both carbohydrate and protein intake affected PO activity in females but only protein affected PO activity in males. Our results indicate that sex differences in Q-fly immune function are not solely explained by sex differences in nutrient intake, although nutrition does contribute to the magnitude of these sex differences.  相似文献   

16.
Capsule Dunnocks Prunella modularis showed a preference for nesting in hedgerows adjacent to sown rather than grass margins on four farms in southwest England.  相似文献   

17.
Five different types of pollen tetrads were detected from the short and long stamens of the male and hermaphrodite flowers of the androdioecious species, Mimosa pigra L. Light (LM) and scanning electron microscopes (SEM) were used in this study to redescribe the pollen forms and to identify the various pollen types encountered. An identification key and relative percentages of these pollen types were also presented. The study showed that the long stamens of the male flowers and those of the hermaphrodite ones have five (I, II, III, IV and V) and two (I and V) pollen types respectively, whereas the short stamens of both male and hermaphrodite flowers have only one pollen type (type I). We report here the first incidence of intra‐specific pollen polymorphism in androdioecious species.  相似文献   

18.
Male and female interests can either be in conflict or serve as a basis for exchange. Communication is thus an important aspect of intersexual relationships. Verreaux's sifaka (Propithecus verreauxi verreauxi), like many prosimians, uses chemical signals as one form of communication. The goals of this study were to determine 1) if males and females exhibit sex differences in their scent-marking behavior, and 2) if scent-marking is an example of mating conflict or cooperation. All occurrences of scent-marks, scent-mark context, and scent-mark style were collected on 23 sifaka in the Kirindy Forest of western Madagascar for 7 months (September 2001-March 2002). Scent-mark rates were collected using continuous focal animal sampling from November 2000-March 2002. Home-range data were collected using monthly censuses and instantaneous focal sampling throughout those 17 months. The pressures of behavioral ecology seem to have shaped scent-marking in sifaka: the sexes exhibited significantly different scent-marking behavior. Results from this study are consistent with the hypotheses that 1) females scent-mark to advertise their presence and mark their resources, 2) clean-chested males use scent-marks as between-group communication to advertise their presence, and 3) stained-chested males use scent-marks as a form of olfactory mate-guarding. Scent-marking does not appear to be a "service" that males provide to females, because overmarking limits female communication rather than adding to the overall number of scent-marks. Scent-marking behavior is a crucial aspect of the mating conflict and for understanding intersexual relationships in sifaka.  相似文献   

19.
Abstract

Three dimensions of isolated spousal separation largely determine its fertility impact: (1) length, (2) “completeness” (degree to which it is eliminating fecundability during fecundable months), and (3) its timing as defined by the reproductive state of the wife at its start. While it is obvious that by starting when the wife is in the fecundable state its net delaying of next conception is maximized, it is much less clear with which reproductive state its start should coincide in order to minimize its fertility impact. By means of a simple model, it is shown that for minimum impact a separation should start later in a pregnancy the longer is post‐partum anovulation, the higher is the level of intrauterine mortality, and the shorter is the period of separation. Conditions of natural fertility are assumed.  相似文献   

20.
Humans tend to cradle infants on the left side of the body. However, it is controversial as to whether left-side cradling is characteristic of women and not of men. Photographic surveys of women and men holding infants have suffered because of underrepresentation of men and lack of accurate information of infants' age. Sampling from “family albums” overcomes these difficulties. A sample of photographs of 1119 women and 577 men indicated (a) left-holding frequencies of 61% women and 47% men, (b) women tended to pose with younger infants, (c) left-side holding was greatest for very young infants (3 months or less) but women showed consistently higher left-side holding for all infant age groups, (d) the distribution of frequency of cradling per individual is skewed towards left-holding for women but for men it is rectangular or perhaps skewed towards right-holding, and (e) there may be family trends in left-holding for women.  相似文献   

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