Data from: Higher incubation temperatures produce long-lasting upward shifts in cold tolerance, but not heat tolerance, of hatchling geckos

Heatwaves are a regular occurrence in Australia, and are predicted to
increase in intensity and duration in the future. These changes may
elevate temperatures inside lizard nests, shortening the incubation
period, so that hatchlings are more likely to emerge during heatwaves.
Potentially, developmental plasticity or heat hardening could buffer
hatchings from future warming. For example, higher incubation temperatures
could shift critical thermal maxima upwards, enabling lizards to withstand
higher temperatures. To investigate whether developmental plasticity
affects hatchling thermal tolerance, we incubated eggs of the velvet gecko
Amalosia lesueurii under two fluctuating incubation treatments to mimic
current warm (mean = 24.3°C, range 18.4 - 31.1°C) and future hot (mean =
28.9°C, range 19.1 - 38.1°C) nest temperatures. We maintained the
hatchlings under identical conditions, and measured their thermal
tolerance (CTmax) at age 14 d and 42 d. We then released hatchlings at
field sites, and recaptured individually marked lizards at age six months,
to determine whether incubation induced shifts in thermal tolerance were
transitory or long-lasting. We found that at age 14 d, hatchlings from the
future hot temperature incubation treatment had higher CTmax (mean = 39.96
± 0.25°C) than hatchlings from the current warm incubation treatment (mean
= 39.70 ± 0.36°C). Hatchlings from the warm-incubation treatment also had
significantly higher heat hardening capacity (mean = 0.79 ± 0.37°C) than
hatchlings from hot-temperature incubation treatment (mean = 0.47 ±
0.17°C). However, both of these incubation-induced effects did not persist
into later life. By contrast, incubation treatment had significant and
long-lasting effects on the cold tolerance of hatchlings. At age 14 d,
warm-incubated hatchlings tolerated colder temperatures (CTmin = 11.24 ±
0.41°C) than hot-incubated hatchlings (CTmin = 14.11 ± 0.25°C). This
significant difference in cold tolerance persisted into the juvenile life
stage, and was present in 6 month old lizards that we recaptured from
field sites. This finding indicates that upward shifts in cold tolerance
caused by higher nest temperatures might impact negatively on overwinter
survival of lizards, but field studies linking fitness to thermal
tolerance are necessary to test this idea. Overall, our results suggest
that developmental plasticity for heat tolerance is unlikely to buffer
lizard populations from increasing temperatures.