Oecologia

, Volume 116, Issue 1, pp 275–283

Null matrices and the analysis of species co-occurrences

  • James G. Sanderson
  • Michael P. Moulton
  • Ralph G. Selfridge
Article

DOI: 10.1007/s004420050589

Cite this article as:
Sanderson, J., Moulton, M. & Selfridge, R. Oecologia (1998) 116: 275. doi:10.1007/s004420050589

Abstract

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).

Key words Community structure Null matrix Species co-occurrences 

Copyright information

© Springer-Verlag Berlin Heidelberg 1998

Authors and Affiliations

  • James G. Sanderson
    • 1
  • Michael P. Moulton
    • 1
  • Ralph G. Selfridge
    • 2
  1. 1.Department of Wildlife Ecology and Conservation, PO Box 11043, University of Florida, Gainesville, FL 32611-0430, USAUS
  2. 2.Department of Computing and Information Science, PO Box 116120, University of Florida, Gainesville, FL 32611-6120, USAUS

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