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Diversity index
A diversity index is a method of measuring how many different types (e.g. species) there are in a dataset (e.g. a community). Diversity indices are statistical representations of different aspects of biodiversity (e.g. richness, evenness, and dominance), which are useful simplifications for comparing different communities or sites.
When diversity indices are used in ecology, the types of interest are usually species, but they can also be other categories, such as genera, families, functional types, or haplotypes. The entities of interest are usually individual organisms (e.g. plants or animals), and the measure of abundance can be, for example, number of individuals, biomass or coverage. In demography, the entities of interest can be people, and the types of interest various demographic groups. In information science, the entities can be characters and the types of the different letters of the alphabet. The most commonly used diversity indices are simple transformations of the effective number of types (also known as 'true diversity'), but each diversity index can also be interpreted in its own right as a measure corresponding to some real phenomenon (but a different one for each diversity index).[1][2][3][4]
Many indices only account for categorical diversity between subjects or entities. Such indices, however do not account for the total variation (diversity) that can be held between subjects or entities which occurs only when both categorical and qualitative diversity are calculated.
Diversity indices described in this article include:
- Richness, simply a count of the number of types in a dataset.
- Shannon index, which also takes into account the proportional abundance of each class under a weighted geometric mean.
- The Rényi entropy, which adds the ability to freely vary the kind of weighted mean used.
- Simpson index, which too takes into account the proportional abundance of each class under a weighted arithmetic mean
- Berger–Parker index, which gives the proportional abundance of the most abundant type.
- Effective number of species (true diversity), which allows for freely varying the kind of weighted mean used, and has a intuitive meaning.[4]
Some more sophisticated indices also account for the phylogenetic relatedness among the types. These are called phylo-divergence indices, and are not yet described in this article.[5]
- ^ Hill, M. O. (1973). "Diversity and evenness: a unifying notation and its consequences". Ecology. 54 (2): 427–432. Bibcode:1973Ecol...54..427H. doi:10.2307/1934352. JSTOR 1934352.
- ^ Jost, L (2006). "Entropy and diversity". Oikos. 113 (2): 363–375. Bibcode:2006Oikos.113..363J. doi:10.1111/j.2006.0030-1299.14714.x.
- ^ Tuomisto, H (2010). "A diversity of beta diversities: straightening up a concept gone awry. Part 1. Defining beta diversity as a function of alpha and gamma diversity". Ecography. 33 (1): 2–22. Bibcode:2010Ecogr..33....2T. doi:10.1111/j.1600-0587.2009.05880.x.
- ^ a b Tuomisto, H (2010). "A consistent terminology for quantifying species diversity? Yes, it does exist". Oecologia. 164 (4): 853–860. Bibcode:2010Oecol.164..853T. doi:10.1007/s00442-010-1812-0. PMID 20978798. S2CID 19902787.
- ^ Tucker, Caroline M.; Cadotte, Marc W.; Carvalho, Silvia B.; Davies, T. Jonathan; Ferrier, Simon; Fritz, Susanne A.; Grenyer, Rich; Helmus, Matthew R.; Jin, Lanna S. (May 2017). "A guide to phylogenetic metrics for conservation, community ecology and macroecology: A guide to phylogenetic metrics for ecology". Biological Reviews. 92 (2): 698–715. doi:10.1111/brv.12252. PMC 5096690. PMID 26785932.
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