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，是阐明物候（phenology）选择与生理生态位（physiological niche）之间的互作机制。对于卵生动物（oviparous species）而言，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。本研究提出假说：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条件下的表现更优（此即时间匹配效应（temporal matching））。
2. 本研究以栖息于中国温带荒漠草原的草原沙蜥（Phrynocephalus przewalskii）为研究对象，验证环境温度季节变化下的时间匹配效应。我们采用拆分卵互置实验方案：将早繁殖雌性与晚繁殖雌性所产的卵，分别置于升温与降温温度制度（temperature regimes）下进行孵化，以此区分内在因素（遗传与母体效应）与外在因素（发育可塑性（developmental plasticity）或驯化（acclimatization））对子代表现与适合度的影响。
3. 早繁殖雌性所产的卵品质优于晚繁殖雌性的卵，这可能源于母体营养供给更充足。早繁殖雌性的子代，其体温选择（selected body temperatures）与代谢率（metabolic rates）均高于晚繁殖雌性的子代。
4. 相较于升温条件，降温（通常预示生长季结束）会缩短所有卵的孵化时长（incubation duration），并提升早、晚产卵胚胎的代谢率。晚孵化幼体在降温条件下的生长速率高于升温条件，而早孵化幼体的生长速率对孵化温度不敏感。因此，尽管早繁殖胚胎整体品质更优，但在降温条件下，晚繁殖胚胎的生长与存活率与早繁殖胚胎相当。
5. 综上，本研究证实了“早繁殖胚胎品质更优”这一结论。内在因素对子代表现与适合度起主导作用，早繁殖胚胎在整个生长季均具备普遍优势。本研究为时间匹配效应提供了部分支持证据：尽管晚繁殖胚胎整体品质更低，但其演化出了适应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当的适合度。