Animals: Turn up the heat on sex determination




A thirty-year-old model of sex determination is finally proven in the Jacky dragon (Amphibolurus muricatus), a short-lived species of lizard found in Australia. The results provide the first unequivocal demonstration that incubation temperature affects male or female fitness and optimises reproductive success.

In mammals and birds, sex is determined by genotype at fertilization. Many reptiles, however, hedge their bets, determining the sex of an individual by interaction with the environment, typically temperature. A model, published by Charnov and Bull in 1977, speculates that environmental sex determination will be favoured by selection, if it could be shown that different temperature regimes maximized reproductive fitness for each sex. However, until now it has been difficult to set up the ‘control’ experiment and produce the ‘wrong’ sex at a given temperature.

Using hormone treatments, Daniel Warner and Richard Shine have overcome previous difficulties and, using the short-lived Jacky dragon, they show that the Charnov–Bull model is correct.



Author contact:

Daniel Warner (Iowa State University, Ames, IA, USA)

Tel: +1 515 294 1968; E-mail: dwarner@iastate.edu