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配置、营养地位和生物的特定特征，如消费者专业化、生长和放牧率。生物的功能特征和相关的权衡对生态系统的功能起着关键作用。该项目旨在评估淡水纤毛虫-微藻捕食系统中种间和种内食性性状变化对生物量和性状动态的重要性。我们将通过调查相关消费者性状对资源供应制度改变的响应的相关性，来研究消费者在抗饥饿性和最大放牧率之间的权衡。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)以牺牲繁殖为代价减少基础代谢的能力，以及2)除了吞噬（混合营养）外，光合作用固定碳的能力。此外，我们将研究诱导进攻（形成能够在野外捕食的巨型形态型）和诱导防御（降低放牧敏感性）如何通过改变物种相互作用与这种权衡相互作用。实验室实验将在不同的资源（猎物和光线）供应制度下操纵不同食物网中种间和种内消费者特征的变化。无论是连续提供还是脉冲提供资源，都会对林分性状变异和生物量性状反馈产生强烈影响。此外，我们将研究在更长的时间内，在更复杂的食物网中，不同等级水平（无性系、物种、群落），种间和种内消费性状变异对生物量和性状动态相互作用的综合影响。所有实验室实验都将辅以数学模型，这些模型将有助于优化实验设计和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关于复杂食物网中生物量和性状动态之间相互作用的现有实验和理论知识，并将大大增强我们对消费者性状变化后果的理解，即受资源波动影响的消费者的适应潜力，对生态系统过程和功能的影响。

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.