Data from: Context-dependent thermolability of sex determination in a lacertid lizard with heteromorphic sex chromosomes

Developmental conditions can profoundly impact key life history traits of
the individual. In cases where offspring sex is driven by developmental
reaction norms, permanent changes to the phenotype can fundamentally alter
life history trajectories. Sex determination mechanisms in reptiles are
remarkable diverse including well-characterized genetic and
temperature-dependent sex determination. In rarer, but increasingly more
commonly documented cases, sex can also be determined by a combination of
the two, with temperature overriding the genetically determined sex. Thus,
sex-by-temperature interactions is a mechanism that can be contextually
labile, where reaction norms of sex against developmental environment
might only be observable under certain conditions. We examine the effects
of incubation temperature on hatchling sex in an oviparous lizard with
clearly defined heteromorphic sex chromosomes presumed to determine sex
solely on a genetic basis. We also test the repeatability of our results
by replicating incubation experiments across three years. We show that
warmer temperatures may override chromosomal sex and cause overproduction
of daughters. However, this effect was inconsistent among years, with high
temperature only resulting in a daughter-significant bias in one year.
Warm-incubated daughters were more efficient at converting yolk into
tissue, which would allow for greater resource allocation to other
fitness-related processes, such as growth. This suggests that thermolabile
sex determination could be a trait under selection. More energy-efficient
embryos also produced faster-growing offspring, suggesting that energy
utilization patterns of the embryo were maintained into the juvenile
stage, which could have important implications for the ontogenetic
development and evolution of life histories.