In many cooperatively-breeding species, the presence of one or more helpers improves the reproductive performance of the breeding pair receiving help. Helper contributions can take many different forms, including allo-feeding, offspring provisioning, and offspring guarding or defence. Yet, most studies have focussed on single forms of helper contribution, particularly offspring provisioning, an...

Prolonged life after reproduction is difficult to explain evolutionarily unless it arises as a physiological side effect of increased longevity or it benefits related individuals (i.e., increases inclusive fitness). There is little evidence that postreproductive life spans are adaptive in nonhuman animals. By using multigenerational records for two killer whale (Orcinus orca) populations in whi...

Genealogical, demographic, and economic data collected in a rural Trinidadian village indicate that: (1) individuals with more land have more offspring, (2) males with more land have higher mating success, (3) young adults with parents resident in the village have higher reproductive success, and (4) the residence o f father has a strong effect on young adult male reproductive success, but appa...

The evolutionary trajectories of reproductive systems, including both male and female multiple mating and hence polygyny and polyandry, are expected to depend on the additive genetic variances and covariances in and among components of male reproductive success achieved through different reproductive tactics. However, genetic covariances among key components of male reproductive success have no...

results genotype frequencies of g/a in fertile and infertile men were significantly different (χ2 = 4.16, df = 1, p = 0.041). genotype frequencies of g/g and a/ain fertile and infertile men were not significantly different (χ2 = 3.32, df = 1, p = 0.068 and χ2 = 0.521, df = 1, p = 0.47, respectively). the risk of infertility was 1.43 folds higher in individuals with the a/a genotype compared to ...

Polyandry, i.e. mating with multiple males within one reproductive event, is a common female mating strategy but its adaptive function is often unclear. We tested whether polyandrous females gain genetic benefits by comparing fitness traits of monandrous (mated twice with a single male) and polyandrous (mated twice with two different males) female bank voles Clethrionomys glareolus. We raised t...

Sexual reproduction strategies vary both between and within species in the level of investment in offspring. Life-history theories suggest that the rate of sexual maturation is critically linked to reproductive strategy, with high investment being associated with few offspring and delayed maturation. For humans, age of puberty and age of first sex are two developmental milestones that have been...

Lewisite, a potent toxic vesicant and chemical warfare agent, is used in a number of research laboratories, is stored in large quantities at depot sites throughout the USA and is occasionally transported to distant sites. Thus, the potential for environmental or occupational exposure exists where lewisite is present. A 42-week two-generation study was conducted to determine the reproductive con...

Global warming can disrupt reproduction or lead to fewer and poorer quality offspring, owing the thermally sensitive nature of reproductive physiology. However, phenotypic plasticity may enable some animals adjust thermal sensitivity maintain performance in warmer conditions. Whether elevated temperature affects depend on timing exposure sex parent exposed. We exposed male female coral reef dam...