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体生态性能的负强迫作用。 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。 在岩石潮间带生境（在岩石海岸上对应最高和最低潮汐的海拔之间的生境）中，由于潮汐动力学和海岸地形，环境应力的梯度沿沿着相对较短的距离发生。 因此，这样的系统是极好的实验评估的影响，非生物胁迫的物种如何聚集在社区。 通过研究，从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，我们将测试的概念模型，预测整体物种多样性和物种多样性的功能组沿着应力梯度在一个全面的方式以前没有实现。 使用海藻冠层，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）可能会从积极影响（促进）转换为从高到低水平的环境压力的负面影响的概念。 了解这一点很重要，因为生物工程师通常被认为总是对生物多样性产生积极影响，这使得他们自动成为保护的目标，尽管他们实际上可能会根据当地的压力水平减少多样性。 使用植物草食动物系统组成的藻类和放牧蜗牛，我们也将调查相关的变化，在防御攻击性状在这样的生物沿着应力梯度，这是相关的理解，因为这种分化可能最终导致创建新的物种，如果定向选择是强有力的。 为了确保我们研究结果的普遍性，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生态复杂性的各个层面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.