Balanced primary sex ratios and resilience to climate change in a major sea turtle population
Marine Ecology Progress Series
© Inter-Research 2017
Reason for embargo
Global climate change is expected to have major impacts on biodiversity. Sea turtles have temperature-dependent sex determination, and many populations produce highly femalebiased offspring sex ratios, a skew likely to increase further with global warming. We estimated the primary sex ratio at one of the world's largest green turtle Chelonia mydas rookeries in Guinea-Bissau, West Africa, and explored its resilience to climate change. In 2013 and 2014, we deployed data loggers recording nest (n = 101) and sand (n = 30) temperatures, and identified hatchling sex by histological examination of gonads. A logistic curve was fitted to the data to allow predictions of sex ratio across habitats and through the nesting season. The population-specific pivotal temperature was 29.4°C, with both sexes produced within incubation temperatures from 27.6 to 31.4°C: the transitional range of temperatures (TRT). Primary sex ratio changed from maleto female-biased across relatively small temporal and spatial scales. Overall it was marginally female-biased, but we estimated an exceptionally high male hatchling production of 47.7% (95% CI: 36.7-58.3%) and 44.5% (95% CI: 33.8-55.4%) in 2013 and 2014, respectively. Both the temporal and spatial variation in incubation conditions and the wide range of the TRT suggest resilience and potential for adaptation to climate change if the present nesting habitat remains unchanged. These findings underline the importance of assessing site-specific parameters to understand populations' responses to climate change, particularly with regard to identifying rookeries with high male hatchling production that may be key for the future conservation of sea turtles under projected global warming scenarios.
Research was funded by the MAVA Foundation, the Rufford Foundation (RSG12317-1, RSG16357-2), and the Portuguese Foundation for Science and Technology through the strategic projects PEst-OE/ BIA/UI0329/2014 granted to cE3c, and UID/MAR/ 04292/ 2013 granted to MARE, project IF/00502/2013/CP1186/ CT0003, and the grant awarded to A.R.P. (fellowship SFRH/ BD/ 85017/2012).
This is the final version of the article. Available from Inter Research via the DOI in this record.
Marine Ecology Progress Series, 2017, Vol. 577, pp. 189 - 203