Data from: Differential early-life survival underlies the adaptive significance of temperature-dependent sex determination in a long-lived reptile

<p><span class="normaltextrun"><span>Many ectotherms rely on temperature cues experienced during development to determine offspring sex. The first descriptions of temperature-dependent sex determination (TSD) were made over 50 years ago, yet an understanding of its adaptive significance remains elusive, especially in long-lived taxa. </span></span><span class="normaltextrun"><span>One novel hypothesis predicts that TSD should be evolutionarily favored when two criteria are met – (a) incubation temperature influences annual juvenile survival and (b) sexes mature at different ages. Under these conditions, a sex-dependent effect of incubation temperature on offspring fitness arises through differences in age at sexual maturity, with the sex that matures later benefiting disproportionately from temperatures that promote juvenile survival.</span></span><span class="eop"><span><span>  </span></span></span><span class="normaltextrun"><span>The American alligator (<em>Alligator mississippiensis</em>) serves as an insightful model in which to test this hypothesis, as males begin reproducing nearly a decade after females. Here, through a combination of artificial incubation experiments and mark-recapture approaches, we test the specific predictions of the survival-to-maturity hypothesis for the adaptive value of TSD by disentangling the effects of incubation temperature and sex on annual survival of alligator hatchlings across two geographically distinct sites.</span></span><span class="normaltextrun"><span><span>  </span></span></span><span class="normaltextrun"><span>Hatchlings incubated at male-promoting temperatures consistently exhibited higher survival compared to those incubated at female-promoting temperatures. This pattern appears independent of hatchling sex, as females produced from hormone manipulation at male-promoting temperatures exhibit similar survival to their male counterparts.</span></span><span class="normaltextrun"><span><span> </span></span></span><span class="normaltextrun"><span>Additional experiments show that incubation temperature may affect early-life survival primarily by affecting the efficiency with which maternally transferred energy resources are used during development. </span></span><span class="normaltextrun"><span>Results from this study provide the first explicit empirical support for the adaptive value of TSD in a crocodilian <span>and point to developmental energetics as a potential unifying mechanism underlying persistent survival consequences of incubation temperature.</span></span></span></p>