Key Laboratory of Animal Ecology and Conservation Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, People's Republic of China.
Center for Excellence in Animal Evolution and Genetics, Chinese Academy of Sciences, Kunming 650223, People's Republic of China.
Proc Biol Sci. 2019 Nov 20;286(1915):20192078. doi: 10.1098/rspb.2019.2078.
Natural nests of egg-laying birds and reptiles exhibit substantial thermal variation, at a range of spatial and temporal scales. Rates and trajectories of embryonic development are highly sensitive to temperature, favouring an ability of embryos to respond adaptively (i.e. match their developmental biology to local thermal regimes). Spatially, thermal variation can be significant within a single nest (top to bottom), among adjacent nests (as a function of shading, nest depth etc.), across populations that inhabit areas with different weather conditions, and across species that differ in climates occupied and/or nest characteristics. Thermal regimes also vary temporally, in ways that generate differences among nests within a single population (e.g. due to seasonal timing of laying), among populations and across species. Anthropogenic activities (e.g. habitat clearing, climate change) add to this spatial and temporal diversity in thermal regimes. We review published literature on embryonic adaptations to spatio-temporal heterogeneity in nest temperatures. Although relatively few taxa have been studied in detail, and proximate mechanisms remain unclear, our review identifies many cases in which natural selection appears to have fine-tuned embryogenesis to match local thermal regimes. Developmental rates have been reported to differ between uppermost versus lower eggs within a single nest, between eggs laid early versus late in the season, and between populations from cooler versus warmer climates. We identify gaps in our understanding of thermal adaptations of early (embryonic) phases of the life history, and suggest fruitful opportunities for future research.
产卵鸟类和爬行动物的天然巢穴表现出显著的热变化，其范围涉及到不同的时空尺度。胚胎的发育速度和轨迹对温度非常敏感，这有利于胚胎能够适应（即根据当地的热环境调整其发育生物学特性）。在空间上，巢穴内的热变化可能非常显著（从顶部到底部），相邻巢穴之间（受遮蔽、巢穴深度等因素的影响），栖息在不同天气条件下的种群之间，以及在栖息环境和/或巢穴特征不同的物种之间，都存在差异。热环境还随时间变化，这会导致单个种群内的巢穴之间存在差异（例如，由于产卵的季节性时间），种群之间和物种之间也存在差异。人为活动（例如栖息地清理、气候变化）增加了热环境在时空上的多样性。我们回顾了有关胚胎对巢穴温度时空异质性的适应的已发表文献。尽管相对较少的类群得到了详细研究，并且潜在机制仍不清楚，但我们的综述确定了许多自然选择似乎使胚胎发生与当地热环境相匹配的情况。据报道，在单个巢穴中，最上面的卵与下面的卵、同一季节中较早产卵与较晚产卵、以及来自较凉爽气候和较温暖气候的种群之间，发育速度存在差异。我们发现，我们对生命史早期（胚胎）阶段的热适应的理解存在差距，并提出了未来研究的有价值的机会。
