Inducible chemical defences in primary producer - herbivore interactions: effects on population dynamics as a function of consumer trait diversity

化学防御是植物-食草动物相互作用中一类主要的诱导防御。尽管被广泛传播，他们还没有被调查的影响，在捕食系统的种群动力学。在这里，我们使用一个蓝藻作为初级生产者和水蚤作为草食动物的水生系统。铜绿微囊藻（Microcystis aeruginosa）产生已知的蛋白酶抑制剂（PI）作为抗草食动物防御，所述蛋白酶抑制剂在暴露于主动放牧草食动物时被诱导，这导致放牧草食动物与初级生产者水平的防御程度之间的反馈回路。在初级生产者水平上的这种可塑性特征防御可以通过测量蓝细菌的抑制剂含量来量化。在这里，我们使用与大型蚤共培养，以研究如何诱导化学防御的M。铜绿假单胞菌在初级生产者和消费者水平上影响种群动态以及性状防御如何波动。为了比较，将使用非防御蓝藻。我们进一步测试人口动态和性状防御的影响性状变异性在消费者层面上比较一个系统与一个系统与许多D。在对PI的性状耐受性方面不同的magna基因型。我们将通过改变各种参数来进行受控生长实验，目的是量化初级生产者水平上的性状防御的权衡，并量化消费者水平上的性状耐受性的权衡。我们假设，这种食草动物介导的化学抗食草动物防御的诱导反馈到消费者水平。更具体地说，我们预计，这种诱导性状的化学防御在蓝藻（i）强烈影响捕食者-被捕食者循环，并导致抑制人口波动的猎物和捕食者丰度相比，一个不设防的蓝藻在一个单一的猎物-捕食者系统。(ii)强烈影响捕食者-猎物循环在一个系统中，许多捕食者的性状宽容不同。我们预计，在消费者水平上增加性状多样性将导致反应模式（波动/非波动）的灵活性增加，从而增加系统的稳定性。

Chemical defences are a major class of inducible defences in plant-herbivore interactions. Despite being wide spread, they have not yet been investigated for their effects on population dynamics in predator-prey systems. Here we use a planktonic system with a cyanobacterium as primary producer and with Daphnia as herbivore. The cyanobacterium Microcystis aeruginosa produces known protease inhibitors (PIs) as anti-herbivore defence that are induced upon exposure to actively grazing herbivores, which results in a feedback loop between grazing herbivores and the degree of defence at the primary producer level. This plastic trait defence at the primary producer level can be quantified by measuring the inhibitor content of the cyanobacterium. Here we use a co-culture with Daphnia magna to investigate how the inducible chemical defence of M. aeruginosa affects population dynamics at the level of primary producer and consumer and how the trait defence fluctuates. For comparison a non-defended cyanobacterium will be used. We further test how population dynamics and the trait defence are affected by trait variability at the consumer level by comparing a system with one versus a system with many D. magna genotypes that differ with respect to the trait tolerance to the PIs. We will run controlled growth experiments by varying a variety of parameters with the aim to quantify the trade-off of the trait defence at the primary producer level and to quantify the trade-off of the trait tolerance at the consumer level.We hypothesize that this herbivore-mediated induction of a chemical anti-herbivore defence feeds back on the consumer level. More specifically we anticipate that this inducible trait chemical defence in the cyanobacterium(i) strongly affects predator-prey cycles and leads to dampened population fluctuations of prey and predator abundances in comparison to an undefended cyanobacterium in a single prey-predator system. (ii) strongly affects predator-prey cycles in a system with many predators that differ in the trait tolerance. We expect that increasing trait-diversity at the consumer level will result in increased flexibility of reaction patterns (fluctuating/non-fluctuating) and therefore in increased system stability.