Disturbance, competition and the invertebrate predator guild of high gradient coastal streams

了解决定生物多样性和群落物种组成的生态和进化因素是当今最重要的科学挑战之一，部分原因是它是预测人类活动将对生态系统产生的后果的先决条件。这也是最艰巨的挑战之一。尽管干扰（如火灾、飓风、洪水）是许多生态系统的正常组成部分，但它们对群落结构具有不同的短期和长期影响。干扰被定义为个体或生物量消失的离散事件，可以排除物种，导致更多物种的加入，改变相对丰度，和/或改变群落的物理或生物环境。在这项研究中，我从对与掠食性无脊椎动物（石蝇和球蝇）共存的影响来看，对溪流（洪水）的干扰的后果。由于竞争能力和对干扰的反应之间的权衡会影响共存竞争者的数量，因此关键的衡量标准是对干扰的敏感性和对竞争的敏感性。我建议使用三管齐下的方法来检查流量变化形式的干扰在高梯度沿海溪流中无脊椎捕食者共存中的作用。我将确定(1)无脊椎捕食者的物种丰富度是否（以及如何）与干扰制度有关，(2)干扰影响捕食者群体内物种共存的主要机制，以及(3)干扰如何以及为什么在溪流之间变化（地质、地貌、土地利用）。

Understanding the ecological and evolutionary factors that determine the biodiversity and species composition of communities is one of the most important scientific challenges today, in part because it is a pre-requisite to predicting the consequences that human activities will have on ecosystems. It is also one of the most daunting challenges. Even though disturbances (e.g. fires, hurricanes, floods) are a normal part of many ecosystems, they have variable short and long term effects on community structure. Disturbance, defined as a discrete event removing individuals or biomass, can exclude species, lead to the inclusion of more species, alter relative abundances, and/or change the physical or biotic environment of a community. In this study I look at the consequences of disturbance in streams (floods) in the light of its effect on coexistence with the guild of predatory invertebrates (stoneflies and caddisflies). Since trade-offs between competitive ability and response to disturbance can affect the number of coexisting competitors, the critical measurements are sensitivity to the disturbance and sensitivity to competition. I propose to use a 3-pronged approach to examining the role that disturbance in the form of flow variability plays in the coexistence of invertebrate predators in high gradient, coastal streams. I will determine (1) if (and how) species richness of invertebrate predators is related to disturbance regime, (2) the primary mechanisms by which disturbance affects species coexistence within the predator guild and (3) how and why disturbance varies among streams (geology, geomorphology, land use).