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The observed species richness is affected not only by the number of individuals but also by the heterogeneity of the sample. If individuals are drawn from different environmental conditions (or different habitats), the species richness of the resulting set can be expected to be higher than if all individuals are drawn from similar environments.
Species evenness is the relative number of individuals of each species in a given area. [1] Species richness [2] is the number of species present in a given area. Species diversity [3] is the relationship between species evenness and species richness. There are many ways to measure biodiversity within a given ecosystem.
The rank abundance curve visually depicts both species richness and species evenness. Species richness can be viewed as the number of different species on the chart i.e., how many species were ranked. Species evenness is reflected in the slope of the line that fits the graph (assuming a linear, i.e. logarithmic series, relationship).
Richness R simply quantifies how many different types the dataset of interest contains. For example, species richness (usually noted S) is simply the number of species, e.g. at a particular site. Richness is a simple measure, so it has been a popular diversity index in ecology, where abundance data are often not available. [7]
Raw species richness counts, which are used to create accumulation curves, can only be compared when the species richness has reached a clear asymptote. Rarefaction curves produce smoother lines that facilitate point-to-point or full dataset comparisons. One can plot the number of species as a function of either the number of individuals ...
Meanings of species diversity may include species richness, taxonomic or phylogenetic diversity, and/or species evenness. Species richness is a simple count of species. Taxonomic or phylogenetic diversity is the genetic relationship between different groups of species. Species evenness quantifies how equal the abundances of the species are. [1 ...
Species evenness is the relative number of individuals of each species in a given area. [181] Species richness [182] is the number of species present in a given area. Species diversity [183] is the relationship between species evenness and species richness. There are many ways to measure biodiversity within a given ecosystem.
The first approach is to calculate a weighted generalized mean of the within-subunit species proportional abundances, and then take the inverse of this mean. The second approach is to calculate the species diversity for each subunit separately, and then take a weighted generalized mean of these. [4] [13] If the first approach is used, the ...