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Interpreting and estimating measures of community phylogenetic structuring
Author(s) -
Hardy Olivier J.,
Jost Lou
Publication year - 2008
Publication title -
journal of ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.452
H-Index - 181
eISSN - 1365-2745
pISSN - 0022-0477
DOI - 10.1111/j.1365-2745.2008.01423.x
Subject(s) - phylogenetic tree , phylogenetic diversity , weighting , estimator , ecology , biology , statistics , mathematics , medicine , biochemistry , gene , radiology
Summary1 To characterize the spatial phylogenetic structure of communities, Hardy & Senterre (2007) ( J. Ecol. , 95 , 493–506) partition Gini–Simpson diversity and its generalization, Rao's entropy, defining I ST and P ST as the proportion of diversity expressed among sites. 2 Interpreting I ST as a measure of ‘differentiation’ between sites is inadequate because low values are actually compatible with high differentiation (low species sharing) in species rich communities. To avoid an inadequate use of I ST , for example in conservation biology, we offer a more literal interpretation: I ST expresses the ‘local species identity excess’. Similarly, P ST expresses the ‘local phylogenetic similarity excess’. 3 Villéger & Mouillot (2008) ( J. Ecol. , 96 , 845–848, this issue) argue that the equations of Hardy & Senterre (2007) to compute diversity are inadequate when sites differ in size, and they provide new expressions weighting sites by their sizes. We argue that whether sites must be weighted equally or not depends on the question being asked. Moreover, actual size and sample size must be distinguished, the latter being important for defining estimators. 4 Synthesis . The formulations given by Hardy & Senterre (2007) and by Villéger & Mouillot (2008) are both correct in the specific contexts we detail.