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Reproductive Roles (reproductive + role)
Selected AbstractsAbsent and Problematic Men: Demographic Accounts of Male Reproductive RolesPOPULATION AND DEVELOPMENT REVIEW, Issue 1 2000Margaret E. Greene Both men and women are important actors in bringing children into life, yet demographic studies on reproduction have tended to focus on women alone. The aims of this article are: 1) to describe why men have attracted limited interest as subjects of such research; 2) to evaluate existing research on men's roles in developing countries; and 3) to suggest directions for future research on male reproductive roles. Men, once neglected, are now included in research on fertility but from a narrow, overly problem-oriented perspective. A review of the literature, however, raises questions about the adequacy of a problem oriented approach. The authors argue that demography should focus on men not only as women's partners, but also as individuals with distinct reproductive histories. In situations, now increasingly common, where the links between marriage and childbearing erode, the differences in men's and women's reproductive experiences and the costs and benefits of parenting will become more salient for future research. [source] The reproductive role hypothesis explains trophic morphology dimorphism in the northern map turtleFUNCTIONAL ECOLOGY, Issue 5 2008G. Bulté Summary 1Sexually dimorphic traits often reflect factors limiting the reproductive success of animals. Thus, most sexually dimorphic traits can be directly linked to the reproductive role of each sex. Sexual dimorphism in trophic structures (e.g. beak, jaws, teeth), however, often lacks a direct link to reproduction. 2Trophic structures can be linked indirectly to reproductive allocation via energy acquisition. The reproductive role hypothesis (also known as the dimorphic niche hypothesis) posits such an indirect link, but has received heretofore little direct empirical support. We tested this hypothesis in a molluscivorous turtle exhibiting marked female-biased trophic morphology dimorphism. 3Bite force analysis showed that females have stronger jaws than males and dietary analysis revealed that females ingest snails closer to their maximum biting capacity than males. Body condition of both sexes and reproductive output of females increased with relative head width, indicating that fitness is tightly linked to head size and bite force. 4Our study provides strong evidence that reproductive role contributes to sexual dimorphism in trophic morphology. Our findings should apply to any animal in which energy intake is limited by trophic morphology. [source] Sex-Specific Aggression and Antipredator Behaviour in Young Brown TroutETHOLOGY, Issue 7 2001Jörgen I. Johnsson Sex differences in adult behaviour are often interpreted as consequences of sexual selection and/or different reproductive roles in males and females. Sex-specific juvenile behaviour, however, has received less attention. Adult brown trout males are more aggressive than females during spawning and juvenile aggression may be genetically correlated with adult aggression in fish. We therefore tested the prediction that immature brown trout males are more aggressive and bolder than immature females. Because previous work has suggested that precocious maturation increases dominance in salmonids, we included precocious males in the study to test the prediction that early sexual maturation increase male aggression and boldness. Aggression and dominance relations were estimated in dyadic contests, whereas boldness was measured as a response to simulated predation risk using a model heron. Independent of maturity state, males initiated more than twice as many agonistic interactions as females in intersexual contests. However, males were not significantly more likely to win these contests than females. The response to a first predator attack did not differ between sex categories, but males reacted less to a second predator attack than females. Sexual maturity did not affect the antipredator response in males. Since there is no evidence from field studies that stream-living immature male and female salmonids differ in growth rate, it appears unlikely that the sex differences demonstrated are behavioural consequences of sex-specific investment in growth. It seems more likely that sex-specific behaviour arises as a correlated response to sexually selected gene actions promoting differential behaviour in adult males and females during reproduction. Alternatively, sex differences may develop gradually during juvenile life, because a gradual developmental program should be less costly than a sudden behavioural change at the onset of sexual maturity. [source] Absent and Problematic Men: Demographic Accounts of Male Reproductive RolesPOPULATION AND DEVELOPMENT REVIEW, Issue 1 2000Margaret E. Greene Both men and women are important actors in bringing children into life, yet demographic studies on reproduction have tended to focus on women alone. The aims of this article are: 1) to describe why men have attracted limited interest as subjects of such research; 2) to evaluate existing research on men's roles in developing countries; and 3) to suggest directions for future research on male reproductive roles. Men, once neglected, are now included in research on fertility but from a narrow, overly problem-oriented perspective. A review of the literature, however, raises questions about the adequacy of a problem oriented approach. The authors argue that demography should focus on men not only as women's partners, but also as individuals with distinct reproductive histories. In situations, now increasingly common, where the links between marriage and childbearing erode, the differences in men's and women's reproductive experiences and the costs and benefits of parenting will become more salient for future research. [source] | ||||||||||