The relevance of consumer competition and feeding traits, as well as their trade-offs, in determining multispecies trophic interactions

生物多样性丧失对食物网动态和生态系统功能的影响在很大程度上取决于食物网的复杂性和结构、生物的营养地位和具体特征，如消费者专门化、生长和放牧率。生物体的功能特性和相关的权衡对生态系统的功能发挥着关键作用。该项目旨在评估淡水纤毛虫消费者-微藻捕食系统中种间和种内消费者性状变异对生物量和性状动态的重要性。我们将研究消费者之间的权衡饥饿抗性和最大放牧率，通过调查相关的消费者性状的相关性，在资源供应的变化制度。我们将重点关注与不同性状相关的两种类型的饥饿抗性：1）以繁殖为代价减少基础代谢的能力，以及2）除了吞噬营养（混合营养）之外的光合碳固定能力。此外，我们将研究如何诱导进攻（形成巨大的形态型能够intraguild捕食）和诱导防御（降低放牧敏感性）通过改变物种的相互作用与这种权衡。实验室实验将进行操纵间和种内的消费者性状的变化，在不同的食物网下的不同制度的资源（猎物和光）供应。无论是连续提供资源还是脉冲提供资源，都会引起资源耗竭，这将强烈影响立木性状变异和生物量性状反馈。此外，我们将调查在更复杂的食物网在更长的时间内，在不同的层次水平（克隆，物种，社区）的生物量和性状动态之间的相互作用，种间和种内消费性状变异的综合影响。所有实验室实验将辅以数学模型，这将有助于优化实验设计，并确定有关人口和社区动态的基本机制。这种联合方法将扩大现有的实验和理论知识之间的相互作用的生物量和性状动态在复杂的食物网，并将大大提高我们的理解消费者性状变异的后果，即适应潜力的消费者受到资源波动，生态系统的进程和功能。

The impact of biodiversity loss on food web dynamics and ecosystem functioning strongly depends on food web complexity and configuration, the trophic position and specific traits of the organisms, such as consumer specialization, growth and grazing rates. The functional traits of organisms and associated trade-offs play a key role for ecosystem functioning. The proposed project aims at evaluating the importance of inter- and intraspecific consumer trait variation for biomass and trait dynamics in a freshwater ciliate consumer - microalgal prey system. We will study the consumer trade-off between starvation resistance and maximum grazing rate by investigating the relevance of associated consumer traits in response to altered regimes of resource supply. We will focus on two types of starvation resistance that are linked to different traits: 1) the ability to reduce basal metabolism at the expense of reproduction, and 2) the ability of photosynthetic carbon fixation in addition to phagotrophy (mixotrophy). Furthermore, we will investigate how inducible offense (formation of giant morphotypes capable of intraguild predation) and inducible defense (decreasing grazing susceptibility) interact with this trade-off by altering species interactions. Laboratory experiments will be conducted manipulating inter- and intraspecific consumer trait variation in different food webs under different regimes of resource (prey and light) supply. Providing resources either continuously or in pulses, entailing periods of resource depletion, will strongly affect standing trait variation and biomass-trait feedbacks. Furthermore, we will investigate the combined influence of inter- and intraspecific consumer trait variation on the mutual interplay between biomass and trait dynamics at different hierarchical levels (clones, species, communities) in more complex food webs over a longer time. All laboratory experiments will be complemented by mathematical models that will help to optimize the experimental design and to identify underlying mechanisms regarding population and community dynamics. This joint approach will broaden the existing experimental and theoretical knowledge on the interplay between biomass and trait dynamics in complex food webs and will substantially enhance our understanding of the consequences of consumer trait variation, i.e. the adaptive potential of consumers that are subjected to resource fluctuations, for ecosystem processes and functioning.