Excess digestive capacity in predators reflects a life of feast and famine
Excess digestive capacity in predators reflects a life of feast and famine
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DOI：
10.1038/nature10240
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发表时间：
2011-08-04
期刊：
影响因子：
64.8
通讯作者：
Schindler, Daniel E.
中科院分区：
文献类型：
--
作者：
Armstrong, Jonathan B.;Schindler, Daniel E.
捕食者面临的一个主要挑战是当猎物在空间和时间上异质时实现正能量平衡。生态异质性在捕食者的生理设计中产生进化权衡；这是因为利用粮食丰富的豆类的能力需要较高的粮食加工能力，但维持这种能力会带来能源成本，而这些能源成本在粮食短缺期间会造成沉重负担(1,2)。生理学的最新进展表明，当觅食机会的变化是可预测的时，动物可以通过快速调节消化系统来跟踪觅食机会的变化来调整能量权衡(1)。然而，人们越来越认识到动物的觅食机会是不可预测的(3)，这应该有利于保持超过平均消费水平（负荷）的食品加工能力的动物(2,4)。尽管存在定量进化设计的基本原则，但对野生动物消化负荷与容量比率的估计实际上是不存在的(1)。在这里，我们对野外捕食者消化系统的负荷：容量比进行了广泛的评估，汇编了 38 种鱼类的 639 项估计值。我们发现，鱼类捕食者通常保持每日进食量比其平均水平高 2-3 倍的生理能力。对食物加工能力和代谢成本之间权衡的数值模拟表明，只有当捕食者与猎物相遇时，观察到的生理机会主义水平才有利可图，因此捕食者的能量预算本质上比目前假设的变化要大得多。
A central challenge for predators is achieving positive energy balance when prey are spatially and temporally heterogeneous. Ecological heterogeneity produces evolutionary trade-offs in the physiological design of predators; this is because the ability to capitalize on pulses of food abundance requires high capacity for food-processing, yet maintaining such capacity imposes energetic costs that are taxing during periods of food scarcity(1,2). Recent advances in physiology show that when variation in foraging opportunities is predictable, animals may adjust energetic tradeoffs by rapidly modulating their digestive system to track variation in foraging opportunities(1). However, it is increasingly recognized that foraging opportunities for animals are unpredictable(3), which should favour animals that maintain a capacity for food-processing that exceeds average levels of consumption (loads)(2,4). Despite this basic principle of quantitative evolutionary design, estimates of digestive load: capacity ratios in wild animals are virtually nonexistent(1). Here we provide an extensive assessment of load: capacity ratios for the digestive systems of predators in the wild, compiling 639 estimates across 38 species of fish. We found that piscine predators typically maintain the physiological capacity to feed at daily rates 2-3 times higher than what they experience on average. A numerical simulation of the trade-off between food-processing capacity and metabolic cost suggests that the observed level of physiological opportunism is profitable only if predator-prey encounters, and thus predator energy budgets, are far more variable in nature than currently assumed.