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.

1. 季节生物学的核心目标之一，是阐明针对物候（phenology）的选择压力与生理生态位（physiological niche）之间的交互机制。对于卵生动物（oviparous species）而言，整个生长季内的适合度（fitness）差异表明，物候转变会改变胚胎所经历的选择环境。我们提出假说：生理机能可与物候产生协同适应——即相较于适应其他环境的胚胎，适应特定环境的胚胎在对应环境中会表现出更优的生长状态，此即“时间匹配（temporal matching）”效应。
2. 本研究以栖息于中国温带荒漠草原的普拉氏沙蜥（Phrynocephalus przewalskii）为研究对象，检验其是否存在与环境温度季节变化相匹配的时间匹配效应。我们采用分窝互换孵化实验（split clutch reciprocal experiment）设计：将早繁殖雌体与晚繁殖雌体所产的卵，分别置于升温、降温两种温度制度下进行孵化，以此剥离内在因素（遗传与母源效应）与外在因素（发育可塑性或驯化适应）对子代性能与适合度的影响。
3. 早繁殖雌体所产的卵品质优于晚繁殖雌体的卵，这大概率源于母体为卵提供了更优质的抚育资源。早繁殖雌体的子代所偏好的选择体温（selected body temperatures）与代谢率（metabolic rates）均高于晚繁殖雌体的子代。
4. 相较于升温处理，能够预示生长季结束的降温处理会缩短两类卵的孵化时长，并提升其代谢率。晚孵化幼体在降温处理下的生长速率高于升温处理组，而早孵化幼体的生长速率则对孵化温度不敏感。因此，尽管早繁殖胚胎整体品质更优，但在降温环境下，晚繁殖胚胎的生长与存活率可达到与早繁殖胚胎相近的水平。
5. 综上，本研究证实了“早繁殖胚胎品质更优”这一结论。内在因素对子代性能与适合度起主导作用，且早繁殖胚胎在整个生长季中普遍具有适应性优势。本研究为时间匹配效应提供了部分实证支持：低品质的晚繁殖胚胎演化出了适配季末环境的生理策略，使其在季末环境中可获得与早繁殖胚胎相近的适合度。