Effect of trait variability on the dynamics of coupled, bi-trophic plankton - biofilm systems

许多生态过程是由捕食者-被捕食者相互作用引起的。因此，它是相当感兴趣的调查这些相互作用，以获得更深入的了解生态系统的动态和功能。几个例子表明，被捕食物种可以发展防御表型，以减少捕食，从而死亡率。然而，这种防御机制可能会付出相当大的代价，只有在高捕食者密度的存在下才能得到回报，这可能只是暂时的。此外，如果猎物受到不同捕食者的捕食，特别是当防御特征是捕食者特有的和不相容的时候，防御的成本可能会大大增加。那么每个猎物表型都有被至少一个捕食者攻击的危险，在这里，我们测试了这种可变的防御成本的后果，在一个具有高可塑性的猎物对两个捕食者中的任何一个。作为模式生物，我们将使用细菌猎物菌株恶臭假单胞菌，它可以形成对比的表型，即共生细胞和生物膜。作为捕食者，我们将使用一种专门的浮游生物捕食者物种（草履虫tetraurelia，单一血统）和一种专门的生物膜捕食者物种（卡氏阿米巴，单一血统）。结合实验方法与数学建模，我们将采用专业化的两个捕食者物种的捕食者公会内操纵性状的变化。这会影响一个单一的猎物物种，它可以以快速的表型可塑性做出反应，以保护自己免受一种或另一种捕食者的攻击，但不能同时防御两种捕食者。我们假设，这种相互作用的特征变化的捕食者公会与表型可塑性的猎物将导致持续的循环变化，在各自的捕食者和猎物的生物量和特征值。这个微生物食物网的所有成员的非常短的世代时间将使我们能够观察到许多世代的时间序列，从而深入了解两个相互关联的食物链内部和之间的长期相互作用和性状调整。此外，我们将建立一个先进的封闭系统和一个流通恒化器系统，我们可以操纵两者，防御成本和捕食者公会的性状变化。这些恒化器系统将包括生物膜可以在其上发展的可变量的表面和水生生境。它们允许通过以不同的方式稀释浮游生物栖息地（猎物和捕食者）和生物膜栖息地（猎物和捕食者）来操纵损失率。为了将微生物种群动态与生态系统结构和功能联系起来，我们将研究捕食者（浮游生物和生物膜捕食者）的性状变化如何改变微生物食物网中的生物量分配和碳通量效率。据我们所知，这样的实验与相应的数学建模尚未进行至今。

Many ecological processes result from predator-prey interactions. Therefore, it is of considerable interest to investigate these interactions in order to gain a deeper understanding of ecosystem dynamics and functions. Several examples show that prey species can develop defended phenotypes to reduce predation and thus mortality. However, such defense mechanisms may come at considerable costs which pay off only in the presence of high predator densities, which may occur only temporally. Furthermore, costs of defense may dramatically increase if the prey is subject to predation by different predators and especially when defense traits are predator specific and incompatible. Then each prey phenotype is in danger to be attacked by at least one of the predators.Here we test the consequences of such variable costs of defense in a prey with high plasticity against either one of the two predators. As model organisms we will use the bacterial prey strain Pseudomonas putida, which can form contrasting phenotypes, i.e. planktonic cells and biofilms. As predators, we will use a specialized plankton predator species (Paramecium tetraurelia, a single lineage) and a specialized biofilm predator species (Acanthamoeba castellani, a single lineage). Combining experimental approaches with mathematical modeling we will employ the specialization of the two predator species to manipulate the trait variation within the predator guild. This affects a single prey species that can react with a fast phenotypic plasticity in order to defend itself against either one or the other type of predator but not both simultaneously. We postulate that this interaction of the trait variation of the predator guild together with the phenotypic plasticity of the prey will lead to ongoing cyclic changes in the respective predator and prey biomasses and trait values. The very short generation times of all members of this microbial food web will enable us to observe time series with many generations providing insights into long-term interactions and trait adjustments within and among two interrelated food chains. Further we will establish an advanced closed system and a flow-through chemostat system in which we can manipulate both, the costs of defense and the trait variation of the predator guild. These chemostat systems will comprise a planktonic habitat and a variable amount of surface on which biofilm can develop. They allow to manipulate the loss rates by diluting the plankton habitat (prey and predator) and the biofilm habitat (prey and predator) in separate ways. In order to link the microbial population dynamics to ecosystem structure and functions, we will investigate how the trait variation in the predator guild (plankton and biofilm predators) will change the biomass allocation and the carbon flux efficiency within the microbial food web. To our knowledge such experiments with a corresponding mathematical modelling have not been conducted so far.