Species evenness in the context of "Diversity index"

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⭐ Core Definition: Species evenness

Species evenness describes the commonness or rarity of a species; it requires knowing the abundance of each species relative to those of the other species within the community. Abundance values can be difficult to obtain. Area-based counts, distance methods, and mark and recapture studies are the three general categories of methods for estimating abundance.

Species evenness is combined with species richness, (the number of species in the community), in order to determine species diversity, which is an important measure of community structure. Community structure in turn provides the quantitative basis needed to create hypotheses and experiments that help to increase understanding of how communities work.

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👉 Species evenness in the context of 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).

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Species evenness in the context of Species diversity

Species diversity is the number of different species that are represented in a given community (a dataset). The effective number of species refers to the number of equally abundant species needed to obtain the same mean proportional species abundance as that observed in the dataset of interest (where all species may not be equally abundant). 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.

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Species evenness in the context of Species richness

Species richness is the number of different species represented in an ecological community, landscape or region. Species richness is simply a count of species, and it does not take into account the abundances of the species or their relative abundance distributions. Species richness is sometimes considered synonymous with species diversity, but the formal metric species diversity takes into account both species richness and species evenness.

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Species evenness in the context of Rank abundance curve

A rank abundance curve or Whittaker plot is a chart used by ecologists to display relative species abundance, a component of biodiversity. It can also be used to visualize species richness and species evenness. It overcomes the shortcomings of biodiversity indices that cannot display the relative role different variables played in their calculation.

The curve is a 2D chart with relative abundance on the Y-axis and the abundance rank on the X-axis.

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LINKED FROM (PARENTS)
← Species diversity ← Species richness ← Rank abundance curve ← Diversity index
LINKS TO (CHILDREN)
Abundance (ecology) → Community (ecology) → Mark and recapture → Species richness → Species diversity →