Hope S F, Kennamer R A, Grimaudo A T, Hallagan J J, Hopkins W A
Department of Fish and Wildlife Conservation, Virginia Tech, Blacksburg, VA, USA.
Savannah River Ecology Laboratory, University of Georgia, Aiken, SC, USA.
Integr Org Biol. 2020 Feb 5;2(1):obaa003. doi: 10.1093/iob/obaa003. eCollection 2020.
Developmental conditions can have consequences for offspring fitness. For example, small changes (<1°C) in average avian incubation temperature have large effects on important post-hatch offspring phenotypes, including growth rate, thermoregulation, and behavior. Furthermore, average incubation temperatures differ among eggs within the same nest, to the extent (i.e., >1°C) that differences in offspring phenotypes within broods should result. A potential consequence of within-nest incubation temperature variation is inequality in behaviors that could cause differences in resource acquisition within broods. To investigate this, we incubated wood duck () eggs at one of two ecologically-relevant incubation temperatures (35°C or 36°C), formed mixed-incubation temperature broods after ducklings hatched, and conducted trials to measure duckling behaviors associated with acquisition of heat (one trial) or food (three trials). Contrary to our predictions, we found no effect of incubation temperature on duckling behaviors (e.g., time spent occupying heat source, frequency of feeding bouts). However, we found evidence that ducklings incubated at the higher temperature consumed more food during the 1-h feeding trials, and grew faster in body mass and structural size (culmen and tarsus) throughout the study, than those incubated at the lower temperature. Apparent food consumption during the trials was positively related to culmen length, suggesting that differences in food consumption may be driven by structural size. This could result in positive feedback, which would amplify size differences between offspring incubated at different temperatures. Thus, our study identifies incubation temperature as a mechanism by which fitness-related phenotypic differences can be generated and even amplified within avian broods.
发育条件会对后代的适应性产生影响。例如，鸟类平均孵化温度的微小变化（<1°C）会对孵化后重要的后代表型产生很大影响，包括生长速度、体温调节和行为。此外，同一巢穴内的卵之间平均孵化温度存在差异，差异程度（即>1°C）足以导致同窝幼鸟的表型差异。巢穴内孵化温度变化的一个潜在后果是行为不平等，这可能导致同窝幼鸟在资源获取上出现差异。为了对此进行研究，我们将林鸳鸯（）的卵在两个与生态相关的孵化温度（35°C或36°C）之一进行孵化，小鸭孵化后形成混合孵化温度的窝雏，并进行试验以测量与获取热量（一项试验）或食物（三项试验）相关的小鸭行为。与我们的预测相反，我们发现孵化温度对小鸭行为没有影响（例如，占据热源的时间、进食次数）。然而，我们发现有证据表明，在1小时的喂食试验中，在较高温度下孵化的小鸭比在较低温度下孵化的小鸭消耗更多食物，并且在整个研究过程中体重和身体结构尺寸（喙长和跗跖长）增长更快。试验期间的表观食物消耗量与喙长呈正相关，这表明食物消耗量的差异可能由身体结构尺寸驱动。这可能导致正反馈，从而放大不同温度下孵化的后代之间的尺寸差异。因此，我们的研究确定孵化温度是一种机制，通过这种机制可以在鸟类窝雏中产生甚至放大与适应性相关的表型差异。
