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0.15
15
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0.15
The Relative Abundance Calculator determines what percentage of the total community a single species represents. Relative abundance (also called proportional abundance or pi) is a fundamental measure in community ecology that describes the evenness of species distributions within a community.
Understanding relative abundance is essential for calculating diversity indices like Shannon and Simpson, assessing species dominance, identifying rare species, and monitoring community health. A community where one species dominates has low evenness, while a community with similar abundances across species has high evenness.
Relative abundance is calculated as:
RA (%) = (Count of Species / Total Count of All Individuals) × 100
The proportion (pi) is simply the count divided by the total without the percentage conversion:
pi = ni / N
Where ni is the count of the target species and N is the total number of all individuals across all species. The sum of all pi values in a community equals 1.0 (or 100%).
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This species makes up 15% of the community, making it a relatively common species but not dominant.
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At only 0.6% of the community, this is a rare species that may warrant conservation attention.
Relative abundance is the proportion of total individuals in a community that belong to a particular species. It indicates how common or rare a species is compared to all other species present. It is a key component of biodiversity measurement and community analysis.
Relative abundance (pi) is a required input for most diversity indices. The Shannon Index uses -sum(pi x ln(pi)), the Simpson Index uses sum(pi^2), and evenness indices compare observed diversity to maximum possible diversity. All require proportional abundance data.
Absolute abundance is the actual count (or density) of a species, while relative abundance is the proportion of the total community. A species with 100 individuals has the same relative abundance of 10% whether the total community has 1,000 or the percentage is the same, but the absolute abundance differs greatly. Relative abundance is unitless and allows comparison across sites of different sizes.
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