When males provide females with resources at mating, they can become the limiting sex in reproduction, in extreme cases leading to the reversal of typical courtship roles. The evolution of male provisioning is thought to be driven by male reproductive competition and selection for female fecundity enhancement. We used experimental evolution under male- or female-biased sex ratios and limited or...

Despite numerous indices proposed to predict the evolution of mating systems, a unified measure of sexual selection has remained elusive. Three previous studies have compared indices of sexual selection under laboratory conditions. Here, we use a genetic study to compare the most widely used measures of sexual selection in natural populations. We explored the mating and reproductive successes o...

Although Mendel's first law predicts that crosses between XY (or XO) males and XX females should yield equal numbers of males and females, individuals in a wide variety of metazoans transmit their sex chromosomes unequally and produce broods with highly skewed sex ratios. Here, we report two modifications to the cellular programme of spermatogenesis, which, in combination, help to explain why m...

Human mating and reproductive behaviour can vary depending on various mechanisms, including the local sex ratio. Previous research shows that as sex ratios become female-biased, women from economically deprived areas are less likely to delay reproductive opportunities to wait for a high-investing mate but instead begin their reproductive careers sooner. Here, we show that the local sex ratio al...

Fisher predicted that sex ratios should be even when the cost of producing each sex is equal, assuming large panmictic populations. Hamilton showed that when individuals breed exclusively in small groups (local mate competition), the sex ratio does not comply with Fisherian theory, but instead favours a female bias. Local mate competition has been suggested to explain female biases most often i...

In this paper, we develop a general method to determine evolutionary equilibrium sex ratios and to check evolutionary stability, continuous stability and invadability in exact genetic models with or without dominance. This method is then applied to three kinds of models for structured populations: the first one concerns Hamilton's LMC model, except that only a fraction beta of female offspring ...

In Ustilago violacea conjugation involves a period of courtship followed by the cooperative assembly of a conjugation tube between paired sporidia of opposite mating type. During courtship information is exchanged between the paired sporidia directing transcription and translation of a ' sex message'. This information exchange is completed even though the plasma membranes and walls of the matin...

Pollen to ovule (P : O) ratios have been hypothesized to correlate with the degree of outcrossing and thus with the mating system of a plant. Also, P : O ratios are likely to vary with respect to pollination mode (i.e. wind pollination or animal pollination). Furthermore, constraints on the evolution of mating systems depending on life form may affect P : O ratios. We compiled P : O ratios and ...

Cryptococcus neoformans is a human fungal pathogen that undergoes a dimorphic transition from a unicellular yeast to multicellular hyphae during opposite sex (mating) and unisexual reproduction (same-sex mating). Opposite- and same-sex mating are induced by similar environmental conditions and involve many shared components, including the conserved pheromone sensing Cpk1 MAPK signal transductio...