Ecological role of environmental stress in species assemblages: developing theory using rocky intertidal systems

环境胁迫是指非生物环境对生物生态性能施加的负向强迫。它是影响自然界物种分布和生物多样性格局的重要因素之一。在岩石潮间带栖息地（岩石海岸最高和最低潮汐对应的海拔之间的栖息地），由于潮汐动力学和海岸地形，环境应力梯度沿着相对较短的距离发生。因此，这种系统非常适合用于实验评估非生物胁迫对物种如何在群落中聚集的影响。通过我的海洋生态实验室的学生将在新斯科舍省、缅因州和德国进行的研究，我们将测试概念模型，以一种前所未有的全面方式预测整体物种多样性和沿着压力梯度的功能群内的物种多样性。利用海藻树冠，我们还将测试生物工程物种（影响许多其他物种栖息地条件的物种）可能从积极影响（促进）转变为消极影响，从高到低水平的环境压力。了解这一点很重要，因为生物工程师通常被认为对生物多样性总是有积极的影响，这使他们成为保护的自动目标，尽管事实上他们可能会根据当地的压力水平减少多样性。利用由藻类和食草蜗牛组成的植物-食草动物系统，我们还将研究这些生物在应激梯度中防御-攻击特征的相关变化，这与理解相关，因为如果定向选择很强，这种分化可能最终导致新物种的产生。为了确保我们发现的普遍性，我们将在西北大西洋（新斯科舍省）和东北大西洋（德国黑尔戈兰）的岩石海岸进行类似的测试。我的研究计划的最终目标是提高我们对环境压力如何在不同生态复杂性水平上塑造物种组合的理解，寻求确定应该适用于其他生物系统的一般原则。

Environmental stress is the negative forcing that the abiotic environment exerts on the ecological performance of organisms. It is one of the most important factors that affect species distribution and biodiversity patterns in nature. In rocky intertidal habitats (habitats between the elevations corresponding to the highest and lowest tides on rocky seashores), gradients of environmental stress occur along relatively short distances because of tide dynamics and coastal topography. Thus, such systems are excellent for experimentally evaluating the influence of abiotic stress on how species assemble in communities. Through research that students from my Marine Ecology Lab will conduct in Nova Scotia, Maine, and Germany, we will test conceptual models that predict overall species diversity and species diversity within functional groups along stress gradients in a comprehensive way not previously achieved. Using seaweed canopies, we will also test the notion that bioengineer species (species that affect habitat conditions for many other species) may switch from positive effects (facilitation) to negative effects from high to low levels of environmental stress. This is important to know because bioengineers are normally assumed to always have positive effects on biodiversity, which makes them automatic targets for conservation, despite the fact that they may actually decrease diversity depending on local stress levels. Using a plant-herbivore system composed of algae and grazing snails, we will also investigate correlative changes in defense-attack traits in such organisms along stress gradients, which are relevant to understand because such differentiation may ultimately lead to the creation of new species if directional selection is strong. To ensure the generality of our findings, we will do similar tests on Northwest Atlantic (Nova Scotia) and Northeast Atlantic (Helgoland, Germany) rocky shores. The ultimate goal of my research program is to improve our understanding of how environmental stress shapes species assemblages at various levels of ecological complexity, seeking to identify general principles that should be applicable to other biological systems.