Sex ratios

Abstract

Sex ratio theory attempts to explain variation at all levels (species, population, individual, brood) in the proportion of offspring that are male (the sex ratio). In many cases this work has been extremely successful, providing qualitative and even quantitative explanations of sex ratio variation. However, this is not always the situation, and one of the

The ends of a continuum: genetic and temperature‐dependent sex determination in reptiles

“…(1) It is therefore a phenomenon of significance in biological evolution. Although considerable understanding has been developed through comparisons of the mammalian sex-determination systems, (2) there is much to be learned from the many organisms with other forms of sex determination.…”

Bidirectional sex change in mushroom stony corals

“…The reason for this is that there are conceptual and practical difficulties in measuring reproductive success (fitness) in plants and animals, since this often depends upon life-history details that are rarely known (e.g. West et al 2002;Allsop & West 2004). A notable exception to this is in sex-changing organisms, where the theory predicts that organisms should have a sex ratio biased towards the 'first sex' (i.e.…”

“…fitness gain curves, sensu Ghiselin 1969;Warner 1975;Charnov 1982) allows us to formulate hypotheses to test predictions of the sex-allocation theory. Some of the most notable successes of the sex-allocation theory (Charnov 1982) have been in explaining cases in which individuals adjust their offspring sex ratio in response to local conditions (Charnov 1982;West et al 2002;Allsop & West 2004;Collin 2006). However, sexallocation theory has been much less successful in predicting and explaining variation in the overall population sex ratio ( West et al 2002).…”

“…A notable exception to this is in sex-changing organisms, where the theory predicts that organisms should have a sex ratio biased towards the 'first sex' (i.e. the sex at which individuals begin their life ;Charnov 1982;Warner 1988;Munday 2002;West et al 2002;Allsop & West 2004;Collin 2006). Given that the relative number of males and females in a population should be inversely related to the relative reproductive success of each sex (Charnov 1993;Allsop & West 2004), it follows that when the second-sex (i.e.…”

“…Some of the most notable successes of the sex-allocation theory (Charnov 1982) have been in explaining cases in which individuals adjust their offspring sex ratio in response to local conditions (Charnov 1982;West et al 2002;Allsop & West 2004;Collin 2006). However, sexallocation theory has been much less successful in predicting and explaining variation in the overall population sex ratio ( West et al 2002). The reason for this is that there are conceptual and practical difficulties in measuring reproductive success (fitness) in plants and animals, since this often depends upon life-history details that are rarely known (e.g.…”