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Keywords:

  • Gradient analysis;
  • nested subset pattern;
  • network;
  • metacommunity;
  • presence–absence matrix;
  • species turnover

ABSTRACT

Baselga [Partitioning the turnover and nestedness components of beta diversity. Global Ecology and Biogeography, 19, 134–143, 2010] proposed pairwise (βnes) and multiple-site (βNES) beta-diversity measures to account for the nestedness component of beta diversity. We used empirical, randomly created and idealized matrices to show that both measures are only partially related to nestedness and do not fit certain fundamental requirements for consideration as true nestedness-resultant dissimilarity measures. Both βnes and βNES are influenced by matrix size and fill, and increase or decrease even when nestedness remains constant. Additionally, we demonstrate that βNES can yield high values even for matrices with no nestedness. We conclude that βnes and βNES are not true measures of the nestedness-resultant dissimilarity between sites. Actually, they quantify how differences in species richness that are not due to species replacement contribute to patterns of beta diversity. Finally, because nestedness is a special case of dissimilarity in species composition due to ordered species loss (or gain), the extent to which differences in species composition is due to nestedness can be measured through an index of nestedness.