Department of Biology, Reed College, Portland, OR 97202, USA.
BMC Ecol. 2013 May 4;13:18. doi: 10.1186/1472-6785-13-18.
Environmental temperature has profound consequences for early amphibian development and many field and laboratory studies have examined this. Most laboratory studies that have characterized the influence of temperature on development in amphibians have failed to incorporate the realities of diel temperature fluctuations (DTF), which can be considerable for pond-breeding amphibians.
We evaluated the effects of different ecologically relevant ranges of DTF compared with effects of constant temperatures on development of embryos and larvae of the Korean fire-bellied toad (Bombina orientalis). We constructed thermal reaction norms for developmental stage, snout-vent length, and tail length by fitting a Gompertz-Gaussian function to measurements taken from embryos after 66 hours of development in 12 different constant temperature environments between 14°C and 36°C. We used these reaction norms as null models to test the hypothesis that developmental effects of DTF are more than the sum of average constant temperature effects over the distribution of temperatures experienced. We predicted from these models that growth and differentiation would be positively correlated with average temperature at low levels of DTF but not at higher levels of DTF. We tested our prediction in the laboratory by rearing B. orientalis embryos at three average temperatures (20°C, 24°C, and 28°C) and four levels of thermal variation (0°C, 6°C, 13°C, and 20°C). Several of the observed responses to DTF were significantly different from both predictions of the model and from responses in constant temperature treatments at the same average temperatures. At an average temperature of 24°C, only the highest level of DTF affected differentiation and growth rates, but at both cooler and warmer average temperatures, moderate DTF was enough to slow developmental and tail growth rates.
These results demonstrate that both the magnitude of DTF range and thermal averages need to be considered simultaneously when parsing the effects of changing thermal environments on complex developmental responses, particularly when they have potential functional and adaptive significance.
环境温度对早期两栖动物的发育有深远的影响，许多野外和实验室研究都对此进行了研究。大多数描述温度对两栖动物发育影响的实验室研究未能将昼夜温度波动（DTF）的实际情况纳入其中，对于池塘繁殖的两栖动物来说，DTF 可能相当大。
我们评估了不同生态相关的 DTF 范围与恒温对韩国火腹蟾蜍（Bombina orientalis）胚胎和幼虫发育的影响。我们通过对在 14°C 至 36°C 之间的 12 个不同恒温环境中发育 66 小时后的胚胎进行测量，拟合了一个 Gompertz-Gaussian 函数，构建了发育阶段、吻肛长和尾长的热反应规范。我们使用这些反应规范作为零模型来检验 DTF 的发育效应是否大于经历的温度分布中平均恒温效应的总和的假设。我们从这些模型中预测，在 DTF 水平较低时，生长和分化与平均温度呈正相关，但在 DTF 水平较高时则不是。我们在实验室中通过在三个平均温度（20°C、24°C 和 28°C）和四个温度变化水平（0°C、6°C、13°C 和 20°C）下饲养 B. orientalis 胚胎来检验我们的预测。几个对 DTF 的观察反应与模型的预测以及在相同平均温度下的恒温处理的反应都有显著差异。在平均温度为 24°C 时，只有最高水平的 DTF 会影响分化和生长速度，但在较冷和较暖的平均温度下，适度的 DTF 足以减缓发育和尾长的生长速度。
这些结果表明，在解析不断变化的热环境对复杂发育反应的影响时，不仅需要考虑昼夜温度波动范围的大小，还需要同时考虑热平均值，特别是当它们具有潜在的功能和适应性意义时。
