Sanderson James G, Moulton Michael P, Selfridge Ralph G
Department of Wildlife Ecology and Conservation, PO Box 11043, University of Florida, Gainesville, FL 32611-0430, USA, , , , , , US.
Department of Computing and Information Science, PO Box 116120, University of Florida, Gainesville, FL 32611-6120, USA, , , , , , US.
Oecologia. 1998 Aug;116(1-2):275-283. doi: 10.1007/s004420050589.
Patterns in species occurrences on islands have been analyzed by several authors. At issue is the number of non-occurring pairs of species (also known as checkerboards). Previous authors have suggested that if the number of checkerboards differs from what is expected by chance, then island communities might have been structured by competition. Investigators have pursued this problem by first generating random (or null) matrices and then testing a metric derived from the collection of null matrices against the metric calculated from the actual species co-occurrence matrix. The random matrices were constrained by requiring the number of species on each island, and the number of islands on which each species occurred to be equal to their observed values. We show that results from previous studies are generally flawed. We present a fast, efficient algorithm to generate null matrices for any set of fixed row and column sums, and propose a modification of a previously proposed metric as a test statistic. We evaluated the efficacy of our construction method for null creation and our metric using incidence matrices from the avifauna of Vanuatu (formerly New Hebrides).
数位作者分析了岛屿上物种出现的模式。问题在于物种未出现配对的数量（也称为棋盘格）。先前的作者认为，如果棋盘格数量与随机预期的数量不同，那么岛屿群落可能是由竞争构建而成的。研究者通过首先生成随机（或空）矩阵，然后针对从实际物种共现矩阵计算出的度量，检验从空矩阵集合得出的一个度量来研究这个问题。随机矩阵受到约束，要求每个岛屿上的物种数量以及每个物种出现的岛屿数量等于其观测值。我们表明先前研究的结果通常存在缺陷。我们提出一种快速、高效的算法，用于为任何一组固定的行和列总和生成空矩阵，并提议对先前提出的度量进行修改作为检验统计量。我们使用来自瓦努阿图（前新赫布里底群岛）鸟类群落的关联矩阵，评估了我们用于创建空矩阵的构建方法以及我们的度量的功效。
