Regional and Local Influences on Species Richness in Coral Communities Across a Pacific Diversity Gradient

珊瑚群落的物种丰富性传统上被解释为在相对较短的时间内在当地社区内运行的过程。最近对其他组合的研究表明，社区可以通过在不同空间和时间尺度上运行的各种过程来组织。由于珊瑚群落埋藏在较大的地理区域，区域/历史现象和当地过程可能共同影响当地的丰富度，应同时进行分析。这项研究将沿着太平洋区域物种丰富度递增的梯度对六个岛屿群和当地三个不同生境的珊瑚进行采样，以定量评估区域和当地过程对当地丰富度的相对影响。太平洋梯度是这一测试的最佳可能选择，因为区域丰富度有很大的明确趋势。从西到东，该地区的物种丰富度从菲律宾和印度尼西亚的450多种下降到法属波利尼西亚东部的不到100种。将采用分层抽样设计来衡量物种丰富度、组成和相对丰度在四个空间尺度上的变化，跨越5-6个数量级(在一个地点的重复样本之间、在一个岛屿上的地点之间、在一个地区的岛屿之间、在不同地区之间)。将收集有关物种存在和相对丰富度以及选定物种的栖息地宽度和深度范围的数据。这些信息将被用来测试不断增加的区域池对不同尺度上的当地丰富度、均衡度、生境压缩和生境重叠的影响。可定植底物的覆盖率也将被量化，并用于测试当地集合体的“开放性”对其对区域影响的敏感性的影响。分层设计将提供一个强大的框架，用于量化样本中每个空间尺度所占总差异的比例，从而能够严格估计多样性和丰富性模式中的尺度依赖关系。这种区域和地方观点的综合不仅对群落生态学的基础研究有意义，而且对与物种灭绝、栖息地丧失和碎片化以及生态恢复有关的应用问题也有意义。

Species richness in coral communities has traditionally been explained in terms of processes operating within the local community over relatively short periods of time. Recent studies of other assemblages have made it clear that communities can be organized by a variety of processes operating at different spatial and temporal scales. Since coral communities are imbedded in larger geographic regions, regional/historical phenomena and local processes may jointly influence local richness and should be analyzed simultaneously. This study will sample corals in six island groups along a gradient of increasing regional species richness across the Pacific Ocean and in three different habitats at local sites to quantitatively evaluate the relative influence of regional and local processes on local richness. The Pacific Ocean gradient is the best possible choice for this test because of the large unequivocal trend in regional richness. Traveling from west to east, regional richness drops from over 450 species in the Philippines and Indonesia to fewer than 100 species in eastern French Polynesia. A hierarchical sampling design will be employed to measure variation in species richness, composition, and relative abundance at four spatial scales spanning 5-6 orders of magnitude (among replicate samples at a site, among sites on an island, among islands in a region, among regions). Data will be collected on species presence and relative abundance as well as on habitat breadth and depth range of selected species. This information will be used to test the effects of the increasing regional pool on local richness, evenness, habitat compression and habitat overlap at different scales. Percent cover of colonizable substrate will also be quantified and used to test the effects of the "openness" of local assemblages on their sensitivity to regional influences. The hierarchical design will provide a powerful framework for quantifying the proportion of total variation among samples that is attributable to each spatial scale and thus will permit a rigorous estimate of scale-dependency in patterns of diversity and abundance. This synthesis of regional and local perspectives will have relevance not only for basic studies of community ecology but also for applied problems associated with species extinctions, habitat loss and fragmentation, and ecological restoration.