Flexible until it snaps: Dynamics of genes & traits, densities & diversity in communities challenged by environmental change

在SPP动态序列中需要解决的一个主要和关键问题是，多样性是否允许在生态群落中通过性状动态进行反馈，从而促进多样性的维持——特别是在对环境变化的响应中。环境条件的变化，如污染物暴露和水温升高，与未知的加性、增效或拮抗作用相互作用。群落反馈跨越了基因和性状、密度和多样性的动态变化，可能对缓冲群落对环境变化的反应至关重要。在这里，我们关注的是由原生物种组成的模式群落，这些原生物种在生态系统水平上具有不同的主要功能特征（自养、混合养或异养）。该项目的重点在于对环境压力源的动态响应，特别是离子银，以及这些压力源对限制社区动态响应其他压力源（如热浪）能力的影响。所选择的形态和生理特征的变化可能与所观察到的环境线索无关，也可能只是间接相关。过去的方法主要依赖于形态学和生理学数据，因此可能会错过生物体和生态系统响应的一些关键方面。考虑到在给定时间内许多不同的潜在反应和反馈的更广泛的方法对于全面解决这个问题是可取的，甚至是必要的。因此，我们将经典形态学和生态生理学分析与基于高通量测序技术的（元）转录组分析结合起来。在连续六个工作包中，我们(i)确定了目标生物对不同应激源的关键响应和单个物种的动态，（ii）确定了低多样性和高多样性模式群落的基因与性状、密度和多样性之间的动态和反馈，以及（iii）确定了存在食草动物放牧压力的群落水平上基因与性状、密度和多样性之间的动态和反馈。该项目的综合性需要在原生生态学、生态毒理学、生物信息学和生态系统建模方面的专业知识，这是三位申请人和外部合作伙伴所涵盖的。简而言之，我们的假设是：(1)恒定和波动的环境条件对基因表达、性状、密度和最终多样性之间的反馈具有根本不同的影响；(2)施加压力的大小和不同压力源之间的相互作用决定了“灵活性的力量”何时失效。

One of the main and crucial questions to be addressed within the SPP DynaTrait is whether diversity allows feedbacks within ecological communities, through trait dynamics, that in turn promotes the maintenance of diversity - specifically in response to environmental change. Changes in environmental conditions, such as pollutant exposure and water temperature increases interact with unknown additive, synergistic or antagonistic effects on biota. Community feedbacks spanning the dynamics of genes and traits, densities and diversity are presumably of key importance for buffering the community response to, for instance, environmental changes. Here we focus on model communities consisting of protist species that differ in major functional traits that are relevant at the ecosystem level (being autotrophs, mixotrophs or heterotrophs). The focus of the project lies on the dynamic responses to environmental stressors, specifically to ionic silver, and on the effect of such stressors to constrain the communities ability to dynamically respond to additional stressors such as heat waves. Shifts in selected morphological and physiological traits may not or may only indirectly be linked to the environmental cues under view. Past approaches relying mainly on morphological and physiological data alone may therefore miss some key aspects in the organisms and ecosystems response. A much broader approach considering many different potential reactions and feedbacks at a given time would be desireable or even essential to comprehensively address this issue. We consequently combine classical morphological and ecophysiological analyses with (meta-)transcriptome analyses based on high throughput sequencing technologies. In six consecutive working packages we (i) identify key responses of the target organisms and the dynamics of single species upon varying levels of stressors, (ii) identify the dynamics and feedbacks between genes and traits, densities and diversity of low and high diversity model communities, and (iii) identify the dynamics and feedbacks between genes and traits, densities and diversity at the community level in the presence of herbivore grazing pressure. The comprehensive character of the project requires expertise in protist ecology, ecotoxicology, bioinformatics and ecosystem modeling which is covered by the three applicants and the external cooperation partner. In brief, our hypotheses are (1) that constant and fluctuating environmental conditions have fundamentally different effects on the feedback between gene expression, traits, densities and eventual diversity and (2) that the magnitude of imposed stress and the interaction between different stressors determine when "the power of flexibility" breaks down.