Data from: Phenology and the physiological niche are co-adapted in a desert dwelling lizard

1. A major goal of seasonal biology is to understand how selection on
phenology and the physiological niche interact. In oviparous species,
fitness variation across the growing season suggests that phenological
shifts will alter selective environments experienced by embryos. We
hypothesize that physiology could become co-adapted with phenology; such
that embryos perform better in the environmental conditions they are
adapted to compared to embryos adapted to other environments (temporal
matching). 2. Here, we tested for temporal matching to seasonal changes in
the environmental temperatures with toad-headed lizard, Phrynocephalus
przewalskii, which inhabits the temperate desert steppe of China. We used
a split clutch reciprocal experiment, by incubating eggs from early- and
late-breeding females at rising and falling temperature regimes
respectively, to separate the influence of intrinsic (genetic and
parental) versus extrinsic factors (developmental plasticity or
acclimatization) on the performance and fitness of offspring. 3. Eggs from
early-breeding females were with higher quality than those from
late-breeding females, likely due to better maternal provisioning.
Offspring from early-breeding females had higher selected body
temperatures and metabolic rates than those from late-breeding females. 4.
Falling temperatures that may indicate the end of the growing season,
reduced incubation duration and increased metabolic rates for both early
and late eggs, compared to rising temperatures. Late hatchlings had higher
growth rates when incubated at falling compared to rising temperatures,
while growth rates of early hatchlings were not sensitive to incubation
temperature. Thus, growth and survival rates of late embryos were similar
to early embryos under falling temperatures, despite early embryos being
of generally higher quality. 5. Overall, our study confirms that “early is
higher quality”. Intrinsic factors dominate offspring performance and
fitness, with a general advantage for early embryos throughout the season.
We found some support for temporal matching, demonstrating that late
embryos with lower quality have physiological strategies that are
specialized to late-season environments, allowing them to attain similar
fitness in late-season environments to that of early embryos.