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

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. 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.  The American
alligator (Alligator mississippiensis) 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.  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. 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. Results from this study
provide the first explicit empirical support for the adaptive value of TSD
in a crocodilian and point to developmental energetics as a potential
unifying mechanism underlying persistent survival consequences of
incubation temperature.