In sexually polymorphic species, the morphs are maintained by frequency-dependent selection through disassortative mating. In heterodichogamous populations in which disassortative mating occurs between the protandrous and protogynous morphs, a decrease in female fitness in one morph is hypothesized to drive sexual specialization in the other morph, resulting in dimorphic populations. We test th...

Progress towards gender equality involves changes in the traditional parental division - female caring and male breadwinning. One aspect is increased parental leave for fathers, which may benefit the health of mothers, children, and fathers themselves. We examined how social and health characteristics (2002) were associated with paternity leave in excess of the 'father quota' of 60 days (2003-2...

Recent theory predicts that environmental variation and small population size facilitate the coexistence of alternative phenotypes despite unequal mean fitness. However, traditional studies of reproductive strategies often assume that the stability of alternative mating behaviours relies on equal male fitness. We present results from field observations and experimental manipulations of thermal ...

Introduction Abstract: We investigated the extent of multiple paternity within and between fruits of the common milkweed, Asclepias syriaca, at one site. Using isozyme polymorphisms at four loci and the maximum likelihood methods of Williams and Evarts (1989), we found no statistical evidence for multiple paternity within fruits. When pairs of fruits obtained from individual ramets were analyze...

The annual survey provides information on the state of the relationship testing community and tries to ask questions that may be of interest and track trends in testing. As a reminder evaluation of these data is anonymous. None of the members of the Relationship Testing Standards Program Unit is aware of which laboratories submitted data. Presentation of the most current data occurs every year ...

We investigated the structure and seasonality of the proximity network in a group of polygynous western black crested gibbons (Nomascus concolor) using social network analysis. The spatial proximity changed seasonally and was affected by temperature and rainfall. Preferred proximity association was not distributed randomly among individuals. Kinship was one explanation for the social structure,...

Effort spent on raising unrelated offspring can be costly and wasteful, and parents are expected to reduce their level of investment when they have low or uncertain relatedness to the young under their care. Although the relationship between parental certainty and parental investment is theoretically well established, empirical support has been mixed. Here, we report on a series of lab and fiel...

In group living animals, especially among primates, there is consistent evidence that high-ranking males gain a higher reproductive output than low-ranking males. Primate studies have shown that male coalitions and sociality can impact male fitness; however, it remains unclear whether males could potentially increase their fitness by preferentially supporting and socializing with females. Here ...

The evolution of monogamy and paternal care in humans is often argued to have resulted from the needs of our expensive offspring. Recent research challenges this claim, however, contending that promiscuous male competitors and the risk of cuckoldry limit the scope for the evolution of male investment. So how did monogamy first evolve? Links between mating strategies and partner availability may...