Índice Simpson D
- Created by
- Renato Passos, Eng. de Software
- Reviewed by
- Renato Passos, Eng. de Software
Last updated: Apr 18, 2026
Formula
D = 1 - Σp²
About this calculator
The Simpson Diversity Index (D) measures species diversity in an ecosystem, considering both species richness (number of species) and evenness (distribution of individuals). Values range from 0 to 1: higher values indicate greater diversity. The formula calculates the probability that two randomly selected individuals belong to different species.
The formula D = 1 - Σp² uses the proportions (p) of individuals per species. For example, in a forest with 40% species A, 30% B, and 30% C, D = 1 - (0.4² + 0.3² + 0.3²). High D indicates lower dominance by a single species, while low D suggests homogeneity.
This index is used in ecological studies to monitor habitat changes, assess pollution impacts, or plan conservation areas. It is particularly useful when comparing communities with different species structures.
Caveats: The index does not account for spatial distribution of species or ecological interactions. Small samples reduce accuracy, and missing data on rare species affects results.
Frequently asked questions
What does a low Simpson Index value indicate?
A low value (near 0) means one or few species dominate the ecosystem, showing low diversity. Example: a monoculture crop field.
How to compare Simpson Index results?
Compare D values between areas or time periods. Higher D means greater diversity. Ensure samples are comparable in size and methodology.
Can the index be used without data on all species?
No. The index requires proportions of all sampled species. Incomplete data reduces reliability.
What's the difference between Simpson and Shannon indices?
Simpson focuses on species dominance, while Shannon considers richness and evenness. Simpson is more sensitive to dominant species.