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While these models differ in the exact method of diversity estimation, they all include two important components: species richness and species evenness. Species richness is a measure of the number of different types of species in an ecosystem.
9 de feb. de 2021 · First published: 09 February 2021. https://doi.org/10.1111/oik.07202. Citations: 246. Sections. PDF. Tools. Share. Abstract. Three metrics of species diversity – species richness, the Shannon index and the Simpson index – are still widely used in ecology, despite decades of valid critiques leveled against them.
- 236
- 130, Issue3
- 09 February 2021
- Simpson’s Index
- Coefficient of Variation
- Shannon–Wiener Diversity Index
- Pielou Index
- Gini Index
A well-known index of evenness is Simpson’s index , given by This is the probability that any two individuals drawn at random from an infinite population will belong to the same species. In our example if f(x) = λ(x), then for the first population, f(x) = (1∕7)2 + (1∕7)2 + … + (1∕7)2 = 7∕49 = 1∕7 = 0.143. For the second population, f(x) = (1∕14)2 +...
Another index of evenness is the Coefficient of Variation, given by where μ is the mean and σthe standard deviation, If f(x) = V (x), xi = μ for all i, so f(x) = 0. For any population without a perfectly even distribution, f(x) > 0. For example, when x = (1, 1, 1, 1, 1, 1, 8), μ = 2, \(\sigma = \sqrt {6} = 2.449\), and V (x) = 1.225.
A third index of evenness, coming out of information theory, is the Shannon–Wiener Diversity index or, as it is called in information theory, the Shannon Entropy, This index quantifies (in expected value) the information contained in a message, in units such as bits. A fair coin has entropy of one bit. If a coin is unfair and you are asked to bet, ...
An index derived from the Shannon–Weiner index is the Pielou index [29, 30], named after Canadian statistical ecologist Evelyn Chrystalla “E.C.” Pielou. where H′ is the Shannon–Wiener Index and \(H^{\prime }_{\max }\) is the maximum value that H′ attains, i.e., \(\ln {S}\), which occurs when all xi are equal. We will use − J′, so that the more even...
The Gini index was introduced in econometrics by Italian statistician Corrado Gini in 1909 and 1912 . It is defined as follows. Start with counting all of the absolute differences among all the counts xi, The average M∕S2 is called the mean absolute difference. Next, normalize by dividing by the average value of xi, i.e., by The ratio M∕A is calle...
- Fred S. Roberts
- froberts@dimacs.rutgers.edu
- 2019
31 de dic. de 2011 · The relationship between species richness and evenness (RRE) across communities remains, however, a controversial issue in ecology because no consistent pattern has been reported. We conducted a systematic meta-review of RRE in aquatic ecosystems along regional to continental gradients and across trophic groups, differing in body ...
- Janne Soininen, Sophia Passy, Helmut Hillebrand
- 2012
Abstract. Diversity (or biodiversity) is typically measured by a species count (richness) and sometimes with an evenness index; it may also be measured by a proportional statistic that combines both measures (e.g., Shannon‐Weiner index or 𝐻 ′ H ′ ). These diversity measures are hypothesized to be positively and strongly correlated, but ...
- Gray Stirling, Brian J. Wilsey
- 2001
20 de sept. de 2021 · Here we quantify the diversity effect and its components—that is, the contributions of variation in species richness and species turnover—for 22 ecosystem functions of microorganisms, plants...
Hace 2 días · Figure 1: Species evenness and species richness for animalcule communities. Both communities contain five species of animalcules. Species richness is the same. The community on the...
