Local Adaptation May Help Mitigate Feminisation of Sea Turtle Populations Globally

Area of Science:

• Marine Biology
• Climate Change Ecology
• Conservation Science

Background:

• Climate warming poses extinction risks, especially for species with limited adaptation capacity.
• Sea turtles exhibit temperature-dependent sex determination, with warmer temperatures producing more females, potentially leading to population feminization.
• Previous research indicated climate warming may outpace sea turtle adaptation through nesting shifts.

Purpose of the Study:

• To evaluate the capacity of sea turtles to adapt to warming temperatures via local adaptations in pivotal incubation temperatures.
• To analyze global sea turtle hatchling sex ratios and pivotal temperatures in relation to incubation conditions.

Main Methods:

• Analysis of 138 published hatchling sex ratio estimates across seven sea turtle species and all ocean basins.
• Examination of 33 recorded pivotal temperatures globally to assess local adaptation to warmer sites.
• Comparison of observed sex ratios with generalized temperature-dependent sex determination models.

Main Results:

• Warmer nesting sites produced lower proportions of female hatchlings than predicted by generalized models.
• Analysis confirmed generally higher pivotal temperatures at warmer sites, indicating local adaptation.
• Observed sex ratios suggest a greater resilience to climate change than previously assumed.

Conclusions:

• Sea turtles demonstrate local adaptation in pivotal temperatures, which can influence hatchling sex ratios.
• This adaptation may enhance the production of male hatchlings in warmer conditions, supporting population viability.
• Sea turtle hatchling sex ratios appear more resilient to climate change impacts than previously anticipated.