Spatial-scale dependency in diversity of biological community and its determination mechanisms : A broad-scale comparative experiment at rocky intertidal shore

本研究以岩质潮间带群落为模型系统，研究了空间尺度对生物群落结构、动态和多样性的影响。按照嵌套分层抽样设计，在日本太平洋沿岸共设立150个普查样地，进行群落普查、演替试验和环境状况监测。主要研究结果如下：1.区域物种丰富度和海岸间物种周转具有明显的纬向梯度。然而，这些模式并没有在较小的尺度上得到反映。另一方面，在Simpson多样性指数的区域多样性或其空间成分中没有纬度倾斜性的证据。这些结果表明，常见物种的相对丰度不随纬度的变化而变化，而稀有物种的数量随着纬度的降低而增加。2.分析了岩石潮间带组合在不同空间尺度上的相似性。除了两个南部地区外，这些组合被划分为不同的区域群，而它们并不是从每个海岸清楚地分开的。相似性在区域水平上与地理距离呈负相关，但在海岸和岩石水平上与地理距离无关。这些分析强调了广泛的非生物/生物因素在确定岩质潮间带组合相似性模式方面的重要性。3.我们确定了藻类物种的栖息地专一性、丰度和地理范围，并使用Rabinowitz的分类方案将其归类为七种稀有形式。最大的种类是稀有种类，“地理范围大，栖息地专一性广，局部密度低”。珍稀物种的数量和比例与岸面藻类物种丰富度呈正相关，表明岸面藻类物种丰富度可以作为S确定保护区的有用标准。

This study aims to examine the effects of spatial scale on structure, dynamics and diversity of biological communities using rocky intertidal communities as a model system. We established a total of 150 census plots along the Pacific coast of Japan according to nested hierarchical sampling design, and conducted census of community, experiment on succession and monitoring of environmental conditions. Major findings are summarized as follows :1.We found clear latitudinal gradients of regional species richness and species turnover among shores. However, these patterns were not reflected at a smaller-scale. On the other hand, there was no evidence of latitudinal clines in Simpson's diversity index in regional diversity or in its spatial components. These results suggest that relative abundance of common species does not vary along latitude, while the number of rare species increases with decreasing latitude.2.We analyzed how similarities of rocky intertidal assemblages vary at different spatial scales. The assemblages were categorized into distinct regional groups except for the two southern regions, whereas they did not separate clearly from each shore. Similarity was negatively correlated with geographic distance at the regional level, but not at the shore and the rock levels. The analyses highlighted the importance of broad-scale abiotic/biotic factors in determining observed patterns in similarity of rocky intertidal assemblages.3.We determined habitat specificity, abundance, and geographic range for algal species, and classified them into the 'seven forms of rarity' using Rabinowitz's classification scheme. The largest category was the category of rarity with "large geographic range, broad habitat specificity and low local density". The number and proportion of the rare species were positively correlated with algal species richness at shore level, suggesting that shore-level algal species richness can be s useful yardstick for deciding conservation areas.