Wright David H, Patterson Bruce D, Mikkelson Greg M, Cutler Alan, Atmar Wirt
U.S. Fish and Wildlife Service, 3310 El Camino, Suite 130, Sacramento, CA 95821, USA, , , , , , US.
Center for Evolutionary and Environmental Biology, The Field Museum, Roosevelt Road at Lake Shore Drive, Chicago, IL 60605, USA, , , , , , US.
Oecologia. 1997 Dec;113(1):1-20. doi: 10.1007/s004420050348.
We present a broad comparative assessment of nested subsets in species composition among ecological communities. We assembled presence-absence data from a broad range of taxa, geographic regions, and spatial scales; and subjected this collection of datasets to common analyses, including a variety of metrics for measuring nestedness and null hypotheses against which to evaluate them. Here we identify ecological patterns in the prevalence and strength of nested subset structure, and assess differences and biases among the available methodologies. In all, we compiled 279 presence-absence matrices, of which 163 do not overlap in their coverage of species and sites. The survey includes studies on vertebrates, arthropods, mollusks, plants, and other taxa; from north temperate, tropical, and south temperate latitudes. Our results were as follows. Statistically significant nestedness was common. Assemblages from landbridge archipelagos were strongly nested, and immigration experiments were least nested. This adds further empirical support to the hypothesis that extinction plays a major role in producing nested structure. Nestedness was positively correlated with the ratio of the areas of the largest and smallest sites, suggesting that the range in area of sites affects nestedness. Taxonomic differences in nestedness were weak. Higher taxonomic levels showed stronger nesting than their constituent lower taxa. We observed no effect of distance of isolation on nestedness; nor any effects of latitude. With regard to methodology, the metrics Nc and Ut yielded similar results, although Nc proved slightly more flexible in use, and deals differently with tied sites. Similarities also exist in the behavior of N0 ("N") and Up, and between N1 and Ua. Standardized nestedness metrics were mostly insensitive to matrix size, and were useful in comparative analyses among presence-absence matrices. Most metrics were affected by the proportion of presences in the matrix. All analyses of nestedness, therefore, should test for bias due to matrix fill. We suggest that the factors controlling nested subset structure can be thought of as four filters that species pass to occur at a site: a sampling filter, a distance filter, a habitat filter, and an area filter - and three constraints on community homogeneity: evolutionary history, recent history, and spatial variation in the environment. The scale of examination can also have important effects on the degree of nestedness observed.
我们对生态群落物种组成中的嵌套子集进行了广泛的比较评估。我们收集了来自广泛分类群、地理区域和空间尺度的存在-缺失数据；并对这组数据集进行了常规分析，包括各种用于测量嵌套性的指标以及用以评估这些指标的零假设。在此，我们确定了嵌套子集结构的普遍性和强度中的生态模式，并评估了现有方法之间的差异和偏差。我们总共编制了279个存在-缺失矩阵，其中163个在物种和地点覆盖范围上没有重叠。该调查包括对脊椎动物、节肢动物、软体动物、植物和其他分类群的研究；涵盖北温带、热带和南温带纬度地区。我们的结果如下。具有统计学意义的嵌套性很常见。陆桥群岛的群落嵌套性很强，而移民实验的嵌套性最弱。这为灭绝在产生嵌套结构中起主要作用这一假设提供了进一步的实证支持。嵌套性与最大和最小地点面积之比呈正相关，表明地点面积范围会影响嵌套性。嵌套性的分类差异较弱。较高分类级别比较低分类级别表现出更强的嵌套性。我们未观察到隔离距离对嵌套性有影响；也未观察到纬度有任何影响。关于方法，指标Nc和Ut产生了相似的结果，尽管Nc在使用中被证明稍微更灵活一些，并且对并列地点的处理方式不同。N0（“N”）和Up以及N1和Ua的行为也存在相似之处。标准化嵌套性指标大多对矩阵大小不敏感，并且在存在-缺失矩阵的比较分析中很有用。大多数指标受矩阵中存在比例的影响。因此，所有嵌套性分析都应检验由于矩阵填充导致的偏差。我们认为，控制嵌套子集结构的因素可被视为物种在一个地点出现所经过的四个过滤器：采样过滤器、距离过滤器、栖息地过滤器和面积过滤器——以及对群落同质性的三个限制：进化历史、近期历史和环境中的空间变化。检查尺度也可能对观察到的嵌套程度产生重要影响。
