Variability in thermal tolerance of clutches from different mothers indicates adaptation potential to climate warming in sea turtles

The current climate warming is a challenge to biodiversity that could surpass the adaptation capacity of some species. Hence, understanding the means by which populations undergo an increase in their thermal tolerance is critical to assess how they could adapt to climate warming. Specifically, sea turtle populations could respond to increasing temperatures by (1) colonizing new nesting areas, (2) nesting during cooler times of the year, and/or (3) by increasing their thermal tolerance. Differences in thermal tolerance of clutches laid by different females would indicate that populations have the potential to adapt by natural selection. Here, we used exhaustive information on nest temperatures and hatching success of leatherback turtle (Dermochelys coriacea) clutches over 14 years to assess the occurrence of individual variability in thermal tolerance among females. We found an effect of temperature, year, and the interaction between female identity and nest temperature on hatching success, indicating that clutches laid by different females exhibited different levels of vulnerability to high temperatures. If thermal tolerance is a heritable trait, individuals with higher thermal tolerances could have greater chances of passing their genes to following generations, increasing their frequency in the population. However, the high rate of failure of clutches at temperatures above 32 degrees C suggests that leatherback turtles are already experiencing extreme heat stress. A proper understanding of mechanisms of adaptation in populations to counteract changes in climate could greatly contribute to future conservation of endangered populations in a rapidly changing world. High temperatures can cause lowered hatching success in sea turtle nests, therefore understanding the naturally occurring variation of thermal tolerances in populations is important in the face of climate change. Using data from 17 leatherback sea turtle nesting seasons, we show that there is naturally occurring variation in the thermal tolerances of clutches produced by different mothers. If offspring with these high tolerances survive to reproduce and these traits are heritable, then higher thermal tolerances traits can be passed on to future generations, and there is potential to adapt and persist under climate change.image