BACKGROUND In cooperative breeders, subordinates generally help a dominant breeding pair to raise offspring. Parentage studies have shown that in several species subordinates can participate in reproduction. This suggests an important role of direct fitness benefits for cooperation, particularly where groups contain unrelated subordinates. In this situation parentage should influence levels of ...

Natural selection does not necessarily favor maximal reproduction because reproduction imposes fitness costs, reducing parental survival, and offspring quality. Here, we show that parents in a preindustrial population in North America incurred fitness costs from reproduction, and women incurred greater costs than men. We examined the survivorship and reproductive success (Darwinian fitness) of ...

We used 10 microsatellite loci to determine the mating system and male reproductive success in a natural population of the root vole (Microtus oeconomus). By genotyping 21 females and their 111 offspring (5.28+/-0.27 S.E. pups per female), we found evidence for multiple paternity in 38% of the litters sired by two or three males. Paternity was not significantly skewed away from the null expecta...

Human immunodeficiency virus type-1 (HIV-1) affects mostly men and women in their reproductive years. For those who have access to highly active antiretroviral therapy (HAART), the course of HIV-1 infection has shifted from a lethal to a chronic disease. As a result of this, many patients with HIV-1 consider having offspring, as do other patients of reproductive age with chronic illnesses. This...

Human immunodeficiency virus type-1 (HIV-1) affects mostly men and women in their reproductive years. For those who have access to highly active antiretroviral therapy (HAART), the course of HIV-1 infection has shifted from a lethal to a chronic disease. As a result of this, many patients with HIV-1 consider having offspring, as do other patients of reproductive age with chronic illnesses. This...

GUPPIES REPRODUCE FROM BEYOND THE GRAVE Humans can be forgiven for assuming that successful reproduction requires both partners to be alive. Amazingly, this isn’t the case for the Trinidadian guppy. Under laboratory conditions, female guppies are able to store sperm for up to a year, potentially allowing them to produce offspring even if the males are no longer around. However, several other st...

Abstract Theory predicts that parental heritable characteristics should shape sex allocation decisions when their effects on reproduction or survival are offspring sex-dependent. Numerous studies have questioned to what extent displayed by one of the parents matched theoretical expectations. This contrasts with handful investigated whether compatibility between could also trigger selective pres...

Infanticide is easiest to understand when it involves killing the offspring of others [1], but a parent may also kill its own offspring if the sacrifice of currently dependent young leads to higher survival of brood mates [2] or an improvement in the parent's likely future reproduction [3]. However, sex-specific infanticide by parents of their own offspring, although occurring in some human soc...