Department of Biological Sciences, University of Wisconsin, P.O. Box 413, Milwaukee, Wisconsin 53201, USA.
Ecology. 2011 Feb;92(2):450-61. doi: 10.1890/10-0478.1.
In seasonal environments, vertebrates are generally thought to time their reproduction so offspring are raised during the peak of food abundance. The mismatch hypothesis predicts that reproductive success is maximized when animals synchronize their reproduction with the food supply. Understanding the mechanisms influencing the timing of reproduction has taken on new urgency as climate change is altering environmental conditions during reproduction, and there is concern that species will not be able to synchronize their reproduction with changing food supplies. Using data from five sites over 24 years (37 site-years), we tested the assumptions of the mismatch hypothesis in the Tree Swallow (Tachycineta bicolor), a widespread aerial insectivore, whose timing of egg-laying has shifted earlier by nine days since the 1950s. Contrary to the mismatch hypothesis, the start of egg-laying was strongly related to food abundance (flying insect biomass) during the laying period and not to timing of the seasonal peak in food supply. In fact, food abundance generally continued to increase throughout the breeding season, and there was no evidence of selection based on the mistiming of laying with the seasonal peak of food abundance. In contrast, there was selection for laying earlier, because birds that lay earlier generally have larger clutches and fledge more young. Overall, initial reproductive decisions in this insectivore appear to be based on the food supply during egg formation and not the nestling period. Thus, the mismatch hypothesis may not apply in environments with relatively constant or abundant food throughout the breeding season. Although climate change is often associated with earlier reproduction, our results caution that it is not necessarily driven by selection for synchronized reproduction.
在季节性环境中，人们普遍认为脊椎动物会调整繁殖时间，以使后代在食物丰沛的高峰期得到抚养。不匹配假说预测，当动物将繁殖与食物供应同步时，繁殖成功率最高。随着气候变化改变了繁殖期间的环境条件，人们对理解影响繁殖时间的机制产生了新的紧迫感，因为担心物种将无法根据不断变化的食物供应来同步繁殖。我们使用了 24 年来五个地点的数据（37 个地点年），检验了不匹配假说在树燕（Tachycineta bicolor）中的假设，这是一种广泛的空中食虫动物，自 20 世纪 50 年代以来，其产卵时间已经提前了九天。与不匹配假说相反，产卵的开始与产卵期间的食物丰度（飞行昆虫生物量）密切相关，而与食物供应季节性高峰的时间无关。事实上，食物丰度通常在整个繁殖季节持续增加，并且没有证据表明基于产卵与食物丰度季节性高峰的不匹配而进行选择。相反，产卵较早的选择是因为较早产卵的鸟类通常具有更大的卵群并且育雏更多。总体而言，这种食虫动物的初始繁殖决策似乎基于卵形成期间的食物供应，而不是育雏期。因此，不匹配假说在整个繁殖季节食物供应相对稳定或丰富的环境中可能不适用。尽管气候变化通常与繁殖期提前有关，但我们的研究结果警告说，这不一定是由于同步繁殖选择所致。
