Population viability at extreme sex-ratio skews produced by temperature-dependent sex determination

The battle of the sexes heats up

31 October 2017

In some species, ratios of male to female embryos vary with changing temperatures, raising concerns they could become extinct due to global warming. Now, Graeme Hays at Deakin University and colleagues in Australia, Greece and the UK demonstrate that in the case of the sea turtle these concerns are unfounded, but may become relevant under extreme climate warming scenarios.

The team incorporated data on sea turtle embryo and hatchling sex ratios from 75 nesting sites, in addition to population sizes, into a mathematical model to predict how they were affected by changing temperatures.

Warmer temperatures promote higher numbers of female embryos, but as temperatures rise further, so do hatchling mortality rates. Slightly varying temperatures across nests means that enough males could develop and survive nearby for future breeding. Adult male sea turtles can breed with multiple females, and twice as frequently, so even with a bias toward female embryos at relatively warm temperatures, sea turtles can maintain have healthy population sizes. It is only at extremely high temperatures that high mortality within developing eggs could threaten sea turtles, the researchers find.

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References

1. Proceedings of the Royal Society B 284, 2016.2576. doi: 10.1098/rspb.2016.2576