Average taxonomic diversity and distinctness
Warwick, R.M. (2008) Average taxonomic diversity and distinctness. In: Jorgensen, S.V. and Fath, B., (eds.) Encyclopedia of Ecology. Elsevier, Oxford, UK, pp. 300-305.
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Taxonomic relatedness of the individuals or species in a sample is the key concept on which taxonomic diversity and distinctness measures of biodiversity are based. It is well known that in impacted assemblages of organisms the taxonomic spread of species is reduced, and in extreme cases they may be sibling species belonging to the same genus, or at least very closely related. Unimpacted assemblages, on the other hand, have a wider taxonomic spread and the species belong to many different genera, families, orders, classes, and phyla. This concept of taxonomic relatedness is totally independent of the numbers of species present, and measures based on it overcome many of the problems inherent in species-richness measures, at least to some degree. The methods are based on tracing the average path length or taxonomic distance between every pair of individuals or species in a taxonomic classification tree, or measuring the variability in these path lengths. The measures are independent of sample size or sampling effort, and are little affected by small variations in habitat type. They can be used for data consisting simply of species lists and arising from unknown or uncontrolled sampling effort, which usually renders it impossible to read anything into the relative size of these lists. There are possible permutation tests for the significance of departure from expectation.
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