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、营养位置和生物的特定特征，如消费者的专门化、生长和放牧率。生物体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。拟议的项目旨在评估种间和种内消费者特征变化对淡水纤毛虫消费者-微藻捕食系统中的生物量和特征动态的重要性。我们将通过调查相关消费者特征与资源供应制度变化的相关性，来研究消费者在抗饥性和最大放牧率之间的权衡。我们将关注与不同性状相关的两种类型的耐饥性：1)以牺牲生殖为代价降低基础新陈代谢的能力；2)除了吞噬(混合营养)外，光合作用固定碳的能力。此外，我们将通过改变物种间的相互作用来研究诱导进攻(能够在公会内捕食的巨型形态的形成)和诱导防御(降低放牧敏感性)是如何与这种权衡相互作用的。将进行实验室实验，在不同的资源(猎物和光照)供应制度下，操纵不同食物网中物种间和物种内消费者特征的差异。无论是连续提供资源还是以脉冲形式提供资源，都会导致资源枯竭的时期，这将严重影响立地性状变异和生物量性状反馈。此外，我们将在更长的时间内，研究在更复杂的食物网中，种间和种内消费者特征变异对不同层次(克隆、物种、群落)的生物量和特征动态之间相互作用的联合影响。所有实验室实验都将得到数学模型的补充，这些模型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关于复杂食物网中生物量和特征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特征变化的后果的理解，即受资源波动影响的消费者对生态系统过程和功能的适应潜力。

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.