Many reptiles do not have heteromorphic sex chromosomes and for these species sex is determined during embryogenesis by the temperature of egg incubation rather than at conception. The phenomenon of temperature-dependent sex determination (TSD) was discovered almost thirty years ago, but few advances have been made towards the elucidation of its mechanism. In the past few years substantial prog...

Sex-determination mechanisms and sex chromosomes are known to vary among reptile species and, in a few celebrated examples, within populations of the same species. The oriental garden lizard, Calotes versicolor, is one most intriguing this regard, exhibiting evidence multiple sex-determination modes single One possible explanation for unusual distribution that C. different determination confine...

All insects in the order Hymenoptera have haplodiploid sex determination, in which males emerge from haploid unfertilized eggs and females are diploid. Sex determination in the honeybee Apis mellifera is controlled by the complementary sex determination (csd) locus, but the mechanisms controlling sex determination in other Hymenoptera without csd are unknown. We identified the sex-determination...

Most nematodes have XO male/XX female sex determination. C. elegans is anomalous, having XX hermaphrodites rather than females. The hermaphrodite condition appears to result from the modification of a basic male/female sex-determination system, which permits both spermatogenesis and oogenesis to occur within a female soma. This modification is achieved by a germ-line-specific control acting at ...

Sex-determining systems are remarkably diverse and may evolve rapidly. Polygenic sex-determination systems are predicted to be transient and evolutionarily unstable, yet examples have been reported across a range of taxa. Here, we provide the first direct evidence of polygenic sex determination in Tigriopus californicus, a harpacticoid copepod with no heteromorphic sex chromosomes. Using geneti...

Sex determination is a fundamental process governed by diverse mechanisms. Sex ratio selection is commonly implicated in the evolution of sex-determining systems, although formal models are rare. Here, we argue that, although sex ratio selection can induce shifts in sex determination, genomic conflicts between parents and offspring can explain why single-factor systems (e.g. XY/XX or ZW/ZZ) are...

Within vertebrates, major sex determining genes can differ among taxa and even within species. In zebrafish (Danio rerio), neither heteromorphic sex chromosomes nor single sex determination genes of large effect, like Sry in mammals, have yet been identified. Furthermore, environmental factors can influence zebrafish sex determination. Although progress has been made in understanding zebrafish ...

Problem: For temperature-dependent sex determination to respond to selection, there should be genetic variance underlying the threshold that switches development from a male-producing program to a female-producing program. Genetic variance for this threshold in reptiles has never been estimated under field conditions. Methods: We estimated variance components of the thermal sensitivity of the s...

Sex determination is a critical developmental decision with major ecological and evolutionary consequences, yet a large variety of sex determination mechanisms exist and we have a poor understanding of how they evolve. Theoretical and empirical work suggest that compensatory adaptations to mutations in genes involved in sex determination may play a role in the evolution of these pathways. Here,...