DNA methylation reveals evolved buffering responses to climate-driven sex ratio skew in sea turtles

Yen, E. C.; Carvajal, G. A.; Bazely, J. O.; Gilbert, J. D.; Taxonera, A.; Fairweather, K.; Lopes, A.; Afonso, I. O.; Newlands, D.; Bentley, B. P.; Correia, S. M.; Allen, C. D.; Staman, M. K.; Sifuentes-Romero, I.; Martin-Duran, J. M.; Komoroske, L. M.; Wyneken, J.; Eizaguirre, C.

doi:10.64898/2026.01.06.697884

bioRxiv · 10.64898/2026.01.06.697884

DNA methylation reveals evolved buffering responses to climate-driven sex ratio skew in sea turtles

Yen, E. C.·Carvajal, G. A.·Bazely, J. O.·Gilbert, J. D.·Taxonera, A.·Fairweather, K.·Lopes, A.·Afonso, I. O.·Newlands, D.·Bentley, B. P.·Correia, S. M.·Allen, C. D.·Staman, M. K.·Sifuentes-Romero, I.·Martin-Duran, J. M.·Komoroske, L. M.·Wyneken, J.·Eizaguirre, C.

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Abstract

Species with temperature-dependent sex determination (TSD), including all sea turtles which produce females at warmer temperatures, face projections of demographic collapse under climate-driven sex ratio skews. However, the accuracy of such predictions remains uncertain, as current models rely heavily on indirect sex ratio proxies due to the lack of a scalable, non-invasive method for sexing hatchlings. Through whole methylome sequencing, we identified 777 sex-associated DNA methylation markers from blood samples of sex-verified loggerhead turtle (Caretta caretta) hatchlings incubated at three controlled temperatures. Applying these markers to a large-scale field experiment showed that classic nest temperature-based models overestimated female production by an average of up to 60.2%, suggesting the presence of evolved buffering mechanisms against thermal effects on sex determination. Our findings highlight the need to revise climate-driven sex ratio forecasts with empirical field data, such as methylation-based assessments, to better understand and safeguard the hidden resilience of vulnerable TSD species.

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Yen, E. C., Carvajal, G. A., Bazely, J. O., Gilbert, J. D., Taxonera, A., Fairweather, K., Lopes, A., Afonso, I. O., Newlands, D., Bentley, B. P., Correia, S. M., Allen, C. D., Staman, M. K., Sifuentes-Romero, I., Martin-Duran, J. M., Komoroske, L. M., Wyneken, J., Eizaguirre, C.. 2026-01-06. DNA methylation reveals evolved buffering responses to climate-driven sex ratio skew in sea turtles. https://doi.org/10.64898/2026.01.06.697884

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