Are thermal barriers higher in deep sea turtle nestsReport as inadecuate

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Thermal tolerances are affected by the range of temperatures that species encounter in their habitat. Daniel Janzen hypothesized in his -Why mountain passes are higher in the tropics- that temperature gradients were effective barriers to animal movements where climatic uniformity was high. Sea turtles bury their eggs providing some thermal stability that varies with depth. We assessed the relationship between thermal uniformity and thermal tolerance in nests of three species of sea turtles. We considered that barriers were -high- when small thermal changes had comparatively large effects and -low- when the effects were small. Mean temperature was lower and fluctuated less in species that dig deeper nests. Thermal barriers were comparatively -higher- in leatherback turtle Dermochelys coriacea nests, which were the deepest, as embryo mortality increased at lower -high- temperatures than in olive ridley Lepidochelys olivacea and green turtle Chelonia mydas nests. Sea turtles have temperature-dependent sex determination TSD and embryo mortality increased as temperature approached the upper end of the transitional range of temperatures TRT that produces both sexes temperature producing 100% female offspring in leatherback and olive ridley turtles. As thermal barriers are -higher- in some species than in others, the effects of climate warming on embryo mortality is likely to vary among sea turtles. Population resilience to climate warming may also depend on the balance between temperatures that produce female offspring and those that reduce embryo survival.

Author: Pilar Santidrián Tomillo , Luis Fonseca, Frank V. Paladino, James R. Spotila, Daniel Oro



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