Food quantity–quality interactions determine growth rates and reproductive success of consumers and thereby regulate community dynamics and food web structure. Predator–prey models that shape our conceptual understanding of foraging ecology typically rely on the parametrization of fixed consumer responses to either food quantity or food quality. In nature, however, consumers optimize their fitness by responding simultaneously to changes in food quantity and quality. Therefore, we assessed consumer responses to changing food environments using a new fitness optimization model that accounted for food quality–quantity interactions to better capture the regulatory flexibility of consumers. Our simulations demonstrated that the impact of food quality on important consumer traits can be altered or even reversed by changes in food quality. Low food quality, for example, affected feeding rates negatively at low food concentrations but triggered surplus feeding at high food concentrations. The scope of surplus feeding was thereby mainly dependent on dynamics of nutrient digestion and in contrast to previous assumptions, energy costs of feeding played a minor role. Further, the regulation of digestive enzyme production, a crucial factor determining assimilation efficiencies, was strongly dependent on whether nonessential or essential nutrients were limiting growth. Consequently, not only the degree but also the type of nutrient limitation mediated the impact of the food environment on consumers’ fitness. At the community level, food quality was key in shaping predator–prey biomass ratios. High food qualities resulted in top‐heavy systems with larger consumer than prey biomass. Decreases of prey digestibility or the availability of essential nutrients, however, triggered a switch from inverted to classical pyramid shapes of bi‐trophic systems. The impact of food quantity on trophic transfer and emerging structural ecosystem properties thus critically hinges on behavioral and physiological responses of consumers. The inclusion of the regulatory flexibility of consumers is therefore an essential next step to improve predator–prey models and our conceptual understanding of trophic interactions.

中文翻译：

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食品数量与质量的相互作用及其对消费者行为和营养转移的影响

食品数量与质量的相互作用决定了消费者的增长率和生殖成功，从而调节了社区动态和食物网结构。塑造我们对觅食生态的概念理解的捕食者－猎物模型通常依赖于固定消费者对食物数量或食物质量的反应的参数化。然而，从本质上讲，消费者通过同时响应食物数量和质量的变化来优化自己的健康状况。因此，我们使用新的适应性优化模型评估了消费者对不断变化的食品环境的反应，该模型考虑了食品质量与数量之间的相互作用，以更好地把握消费者的监管灵活性。我们的模拟表明，食品质量对重要消费者特征的影响可以通过食品质量的改变来改变甚至逆转。例如，低食品质量在低食品浓度下会对进食率产生负面影响，但在高食品浓度下会引发过量进食。因此，过量饲喂的范围主要取决于养分消化的动态，与以前的假设相反，饲喂的能量成本只占很小的比例。此外，消化酶产生的调节，这是决定同化效率的关键因素，在很大程度上取决于非必需或必需营养素是否会限制生长。因此，不仅营养限制的程度，而且营养限制的类型也介导了食物环境对消费者健康的影响。在社区一级，食品质量是决定捕食者与猎物生物量比率的关键。高品质的食物导致重磅系统的消耗量大于猎物的生物量。猎物消化率的降低或必需营养素的可用性降低，引发了双营养系统从倒金字塔形转变为经典金字塔形的转变。食物数量对营养传递和新兴结构生态系统特性的影响因此关键取决于消费者的行为和生理反应。因此，包括消费者的监管灵活性是改进捕食者－猎物模型以及我们对营养相互作用的概念性理解所必不可少的下一步。