Morisita-Horn Overlap
Compare two communities with the Morisita-Horn similarity coefficient for two categories. Each pair of proportions must sum to one; zero means no shared composition and one means identical composition.
Description
Compare two communities with the Morisita-Horn similarity coefficient for two categories. Each pair of proportions must sum to one; zero means no shared composition and one means identical composition.
Morisita-Horn Overlap is a focused biology tool that compare two communities with the Morisita-Horn similarity coefficient for two categories. Each pair of proportions must sum to one; zero means no shared composition and one means identical composition. It calculates locally from the values you enter and exposes the result without changing the source observations.1
When to use Morisita-Horn Overlap
Use Morisita-Horn Overlap when you need to compare two communities with the Morisita-Horn similarity coefficient for two categories. Each pair of proportions must sum to one; zero means no shared composition and one means identical composition. Enter Community A resource 1 proportion, Community A resource 2 proportion, Community B resource 1 proportion, and Community B resource 2 proportion using the definitions and units below so the result can be reproduced.
- Community A resource 1 proportion
- A finite measured or assumed value from 0 through 1.
- Community A resource 2 proportion
- A finite measured or assumed value from 0 through 1.
- Community B resource 1 proportion
- A finite measured or assumed value from 0 through 1.
- Community B resource 2 proportion
- A finite measured or assumed value from 0 through 1.
How Morisita-Horn Overlap calculates the result
The published tool contract uses this rule: Compare two communities with the Morisita-Horn similarity coefficient for two categories. Each pair of proportions must sum to one; zero means no shared composition and one means identical composition.
- Horn overlap index
- The calculated horn overlap index.
Limitations of Morisita-Horn Overlap
The calculation does not propagate measurement uncertainty, sampling error, or biological and chemical variability. Community A resource 1 proportion must remain between 0 and 1; Community A resource 2 proportion must remain between 0 and 1.
Alternative or Complementary measurements
Retain the original Community A resource 1 proportion, Community A resource 2 proportion, Community B resource 1 proportion, and Community B resource 2 proportion values and their units alongside the result. Morisita-Horn Counts is useful when you instead need to quantify overlap between two communities over two species from raw abundance counts with the Morisita-Horn index. Sorensen Index provides another view by helping you compute the Sorensen-Dice coefficient of community similarity as 2 times the number of shared species divided by the sum of species counts in both communities.
References
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Morisita's overlap index — Wikipedia contributors
Similar or alternative tools
- Morisita-Horn Counts
Quantify overlap between two communities over two species from raw abundance counts with the Morisita-Horn index.
- Sorensen Index
Compute the Sorensen-Dice coefficient of community similarity as 2 times the number of shared species divided by the sum of species counts in both communities.
- Brillouin Index
Compute the Brillouin diversity index HB = (ln(N!) - sum(ln(ni!))) / N from three species counts using loop-based log factorials for communities up to 10000 individuals.