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 th...