Idaho Cooperative Fish and Wildlife Research Unit, Department of Fish and Wildlife Sciences, University of Idaho, 875 Perimeter Drive MS 1141, Moscow, ID, 83844, U.S.A.
U.S. Geological Survey, Idaho Cooperative Fish and Wildlife Research Unit, Department of Fish & Wildlife Sciences, University of Idaho, 875 Perimeter Drive MS 1141, Moscow, ID, 83844, U.S.A.
Biol Rev Camb Philos Soc. 2021 Aug;96(4):1349-1366. doi: 10.1111/brv.12705. Epub 2021 Mar 22.
One enduring priority for ecologists has been to understand the cause(s) of variation in reproductive effort among species and localities. Avian clutch size generally increases with increasing latitude, both within and across species, but the mechanism(s) driving that pattern continue to generate hypotheses and debate. In 1961, a Ph.D. student at Oxford University, N. Philip Ashmole, proposed the influential hypothesis that clutch size varies in direct proportion to the seasonality of resources available to a population. Ashmole's hypothesis has been widely cited and discussed in the ecological literature. However, misinterpretation and confusion has been common regarding the mechanism that underlies Ashmole's hypothesis and the testable predictions it generates. We review the development of well-known hypotheses to explain clutch size variation with an emphasis on Ashmole's hypothesis. We then discuss and clarify sources of confusion about Ashmole's hypothesis in the literature, summarise existing evidence in support and refutation of the hypothesis, and suggest some under-utilised and novel approaches to test Ashmole's hypothesis and gain an improved understanding of the mechanisms responsible for variation in avian clutch size and fecundity, and life-history evolution in general.
一个持久的优先事项一直是了解生态学家生殖努力在物种和地点之间的变化的原因。鸟类的卵数通常随着纬度的增加而增加，无论是在物种内还是跨物种，但驱动这种模式的机制继续产生假说和争论。1961 年，牛津大学的博士生 N.菲利普·阿什莫尔（N. Philip Ashmole）提出了一个有影响力的假说，即卵数与种群可利用资源的季节性直接成比例变化。阿什莫尔的假说在生态学文献中被广泛引用和讨论。然而，对于阿什莫尔假说所依据的机制及其产生的可检验预测，存在着普遍的误解和混淆。我们回顾了一些著名假说的发展，以解释卵数变化，重点是阿什莫尔假说。然后，我们讨论并澄清了文献中关于阿什莫尔假说的混淆来源，总结了支持和反驳该假说的现有证据，并提出了一些未被充分利用和新颖的方法来检验阿什莫尔假说，并深入了解导致鸟类卵数和生育力以及一般生活史进化变化的机制。
