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Research article2009Peer reviewed

Calculating minimum discrepancy to assess the nestedness of species assemblages

Roberge, J. -M.; Bokma, F.; Monkkonen, M.; Jonsson, B. G.


Nestedness is a pattern whereby species-poor assemblages are composed of subsets of the species occurring in richer assemblages. One of the most commonly used measures of the degree of nestedness for presence-absence matrices is the 'discrepancy' metric. A hitherto neglected property of that metric is that it may take several values for a given site-by-species matrix in the presence of ties in the marginal totals. This complicates the quantification of nestedness for the observed presence-absence matrix, as well as the assessment of statistical significance, which is typically achieved through Monte Carlo simulations. A solution to the problem is to calculate the minimum discrepancy using a modified algorithm involving permutations of columns with tied totals.


Ecological communities; Nested subsets; Nestedness metrics; Presence-absence matrices; Species composition

Published in

Community Ecology
2009, Volume: 10, number: 2, pages: 141-145

    UKÄ Subject classification

    Environmental Sciences related to Agriculture and Land-use

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