The adaptive significance of temperature-dependent sex determination in a reptile

Abstract

Understanding the mechanisms that determine an individual's sex remains a primary challenge for evolutionary biology. Chromosome-based systems (genotypic sex determination) that generate roughly equal numbers of sons and daughters accord with theory, but the adaptive significance of environmental sex determination (that is, when embryonic environmental conditions determine offspring sex, ESD) is a major unsolved problem. Theoretical models predict that selection should favour ESD over genotypic sex determination when the developmental environment differentially influences male versus female fitness (that is, the Charnov-Bull model), but empirical evidence for this hypothesis remains elusive in amniote vertebrates--the clade in which ESD is most prevalent. Here we provide the first substantial empirical support for this model by showing that incubation temperatures influence reproductive success of males differently than that of females in a short-lived lizard (Amphibolurus muricatus, Agamidae) with temperature-dependent sex determination. We incubated eggs at a variety of temperatures, and de-confounded sex and incubation temperature by using hormonal manipulations to embryos. We then raised lizards in field enclosures and quantified their lifetime reproductive success. Incubation temperature affected reproductive success differently in males versus females in exactly the way predicted by theory: the fitness of each sex was maximized by the incubation temperature that produces that sex. Our results provide unequivocal empirical support for the Charnov-Bull model for the adaptive significance of temperature-dependent sex determination in amniote vertebrates.

Highly thermosensitive Ca2+dynamics in a HeLa cell through IP3receptors

“…For example, fertilization in mammals is navigated by the temperature gradient (Bahat et al, 2003); an increase in neuronal activity associated with temperature elevations has been observed in the hippocampus (Andersen and Moser, 1995); sex in reptiles is determined by the absolute temperature (Warner and Shine, 2008); and plants react to temperature stresses to maximize growth and developmental processes (Sung et al, 2003). It has recently been clarified that ambient thermoreceptors are expressed as a family of channels in the specific regions in the brain (Hamada et al, 2008), sensory nerve endings, and skin (Dhaka et al, 2006).…”

Sex-chromosome differentiation and ‘sex races’ in the common frog ( Rana temporaria )

“…Purely environmental sex determination (ESD) has been documented in several fish and non-avian reptiles (e.g. [3][4][5][6][7]). Sex chromosomes in these groups are often homomorphic, partly due to frequent turnovers (e.g.…”

Reproductive behavior and development in Spilotes sulphureus (Serpentes: Colubridae) from Ecuador

“…Hatching success is probably related to incubation conditions (Gutzke and Packard 1987, Burger et al 1987, Andrews 2008, Packard and Packard 1988, Werner and Shine 2008.…”