Underwood A J, Chapman M G
Centre for Research on Ecological Impacts of Coastal Cities, Marine Ecology Laboratories, A11, University of Sydney, NSW 2006, Australia e-mail:
Oecologia. 1998 Dec;117(4):570-578. doi: 10.1007/s004420050694.
In several areas of research on ecological assemblages, it is useful to be able to analyse patterns of spatial variation at various scales. Multivariate analyses of dissimilarity or similarity in assemblages of species are limited by problems of non-independence caused by repeated use of the sample-units. Where rank-order procedures are used, no comparative quantitative measurements of dissimilarity at different scales are produced. An alternative method is described that uses the sample's average assemblage (or centroid). These estimates are themselves averaged to give centroids for larger spatial scales. Dissimilarities from the centroids at each scale are then calculated using independent replicates for each scale from those in each sample. The dissimilarity measures can then be examined by analysis of variance to detect spatial scales of differences for each sample at every level of a hierarchy of scales. The method is illustrated using data from mangrove forests and rocky shores, involving up to 97 taxonomic groups (species, other taxa). Differences among assemblages at the scales of sites (tens of meters apart) or locations at shores (hundreds of meters apart) were identified. Consequences of different numbers of replicates are discussed, with some potential problems (and their solutions) in application.
在生态群落的几个研究领域中，能够分析不同尺度上的空间变异模式是很有用的。物种群落中差异或相似性的多变量分析受到样本单元重复使用导致的非独立性问题的限制。在使用排序程序时，不会产生不同尺度上差异的比较定量测量。本文描述了一种替代方法，该方法使用样本的平均群落（或质心）。这些估计值本身被平均以给出更大空间尺度的质心。然后，使用每个样本中每个尺度的独立重复样本，计算每个尺度上与质心的差异。然后，可以通过方差分析来检验差异测量，以检测每个样本在尺度层次结构的每个级别上的差异空间尺度。使用来自红树林和岩石海岸的数据说明了该方法，这些数据涉及多达97个分类群（物种、其他分类单元）。确定了在地点尺度（相距数十米）或海岸位置尺度（相距数百米）上群落之间的差异。讨论了不同重复次数的后果，以及应用中的一些潜在问题（及其解决方案）。
