Liebl Andrea L, Steen Andrew J, O'Neill Louis G, Savage James L, Russell Andrew F
University of South Dakota, Department of Biology, Vermillion, SD 57069, USA.
University of Exeter, Centre for Ecology & Conservation, Penryn, Cornwall TR10 9FE, UK.
Integr Comp Biol. 2024 Dec 20;64(6):1633-1642. doi: 10.1093/icb/icae063.
Understanding how animals maximize reproductive success in variable environments is important in determining how populations will respond to increasingly extreme weather events predicted in the face of changing climates. Although temperature is generally considered a key factor in reproductive decisions, rainfall is also an important predictor of prey availability in arid environments. Here, we test the impact of weather (i.e., rainfall and temperature) on female reproductive investment in an arid-dwelling bird (i.e., clutch size and egg volume) and tradeoffs between the two. We predicted that female chestnut-crowned babblers (Pomatostomus ruficeps), endemic to the arid region of Australia, would increase clutch size at the expense of egg volume in response to variation in rainfall and temperature. We found that over 14 breeding seasons, clutch size decreased with increasing temperature, but increased following more rain. Egg volume, on the other hand, became larger as temperatures increased and, although not related to the amount of rain, was related to the number of days since the last rainfall. Finally, egg size decreased as clutch size increased, indicating a tradeoff between the two reproductive parameters. Our results suggest that chestnut-crowned babblers breed reactively in response to variable environments. We expect that clutch size variation in response to rain may reflect the impact of rain on arthropod abundance, whereas the effect of temperature may represent an established decline in clutch size observed in other seasonal breeders. As the tradeoff between clutch size and egg volume was modest and clutch sizes were modified to a greater extent than egg volumes in response to rainfall, we suggest selection is more likely to increase offspring number than quality, at least in favorable years. Our results support the idea that reproductive investment is variable in fluctuating environments, which has implications for species living in habitats experiencing more extreme and less predictable weather as the global climate changes.
了解动物如何在多变的环境中实现繁殖成功率最大化，对于确定种群将如何应对气候变化下预测的日益极端的天气事件至关重要。尽管温度通常被认为是繁殖决策中的关键因素，但在干旱环境中，降雨也是猎物可获得性的重要预测指标。在此，我们测试天气（即降雨和温度）对一种干旱地区鸟类（即窝卵数和卵体积）雌性繁殖投资的影响，以及两者之间的权衡。我们预测，澳大利亚干旱地区特有的栗冠弯嘴鹛（Pomatostomus ruficeps）雌性会根据降雨和温度的变化，以牺牲卵体积为代价增加窝卵数。我们发现，在14个繁殖季节中，窝卵数随温度升高而减少，但降雨增多后窝卵数增加。另一方面卵体积随着温度升高而变大，虽然与降雨量无关，但与上次降雨后的天数有关。最后，卵大小随着窝卵数增加而减小，表明这两个繁殖参数之间存在权衡。我们的结果表明，栗冠弯嘴鹛会根据多变的环境做出反应进行繁殖。我们预计，窝卵数随降雨的变化可能反映了降雨对节肢动物数量的影响，而温度的影响可能代表了在其他季节性繁殖者中观察到的窝卵数既定的下降趋势。由于窝卵数和卵体积之间的权衡较小，并且在降雨后窝卵数的变化幅度大于卵体积，我们认为至少在有利年份，选择更有可能增加后代数量而非质量。我们的结果支持这样一种观点，即在波动的环境中繁殖投资是可变的，这对生活在全球气候变化导致天气更加极端且更不可预测的栖息地中的物种具有影响。
