Dynamics of phytoplankton size-structure as explained by bio-physical principles and ecological history: a trait based adaptive dynamics modeling approach

不断增加的全球生物多样性损失率是一个紧迫的问题，但对多样性动态进行定量预测的能力有限。这一总主题下的一个特别问题是了解社区对自然界中经常发生的多种压力来源的反应。多个应激源的组合和顺序都会影响多样性动态，从而降低了性状和生态系统动态的总体可预测性。在拟议的项目中，我们的目标将是建立一个新的量化模型框架，该框架理想地适用于生理、生物物理和基于最优化的描述的集成。我们采用了其中一位申请者先前为浮游生物群落开发的基于特征的适应动力学模型(ATBM)方法[Wirtz 2013：Ocean Biology，160：2319-2335]。该模型将浮游植物的平均细胞大小解析为调节与健康相关的许多过程(即生长和死亡)的基本特征。利用这一框架，我们旨在研究不同组织水平的单细胞自养细胞在多种应激源下的影响，尤其是特征多样性的变化。该模型的机制基础将使我们的分析能够扩展到由于进化适应而引起的遗传变化。由于重点将放在浮游植物作为一种世代时间较短的模式生物上，我们的项目将直接与Ulrich Sommer教授(GEOMAR，KIER)提出的中围体实验相互作用。在这里，关于选择性放牧和营养限制对浮游植物群落大小结构的影响，该模型将进一步改进和分析，目的是将观察到的自然浮游植物群落对个别和顺序应用放牧和营养限制的反应作为主要应激源。该模型将进一步应用于野外种群，并有望完善我们对自然界多尺度多样性变化的机械性理解。

Ever-increasing rates of global biodiversity loss is a pressing concern, yet only limited capacity exists for a quantitative prediction of diversity dynamics. A particular issue under this general theme is understanding the response of communities to multiple stressors as often occur in nature. Both the combination and sequence of multiple stressors affect diversity dynamics, which reduces the overall predictability of trait and ecosystem dynamics. In the proposed project, our aim will be to establish a novel quantitative model framework that is ideally suitable for the integration of physiological, biophysical and optimality-based descriptions. We adopt a trait-based adaptive dynamics model (ATBM) approach developed previously for plankton communities by one of the applicants [Wirtz 2013: Marine Biology, 160:2319-2335]. The model resolves mean phytoplankton cell size as the fundamental trait that regulates many processes related to fitness (i.e. growth and mortality). Using this framework, we aim to study the effects of multiple stressors at different organizational level of unicellular autotrophs, with a particular focus on the changes in trait diversity. The mechanistic basis of the model will enable extension of our analysis to genetic shifts due to evolutionary adaptation. As the focus will be on phytoplankton as a model organism with short generation times, our project will directly interact with the mesocosm experiments proposed by Prof. Ulrich Sommer (GEOMAR, Kiel). Here, the model will be subsequently improved and analyzed further with respect to the effects of selective grazing and nutrient limitation on the size-structure of the phytoplankton community, with the aim to hind-cast the observed response of natural phytoplankton communities to individual and sequential application of grazing and nutrient limitation as major stressors. Further model applications of the model to field populations is envisaged and is expected to refine our mechanistic understanding of multi-scale diversity changes in nature.