Simpson 1-D (diversidade)
- Created by
- Renato Passos, Eng. de Software
- Reviewed by
- Renato Passos, Eng. de Software
Last updated: Apr 18, 2026
About this calculator
Simpson's Diversity Index (1-D) measures the probability that two randomly selected individuals from a community belong to different species. This value ranges from 0 to 1, where 0 indicates minimum diversity (single dominant species) and 1 indicates maximum diversity (all species equally abundant). The calculator automates the calculation from species abundance data, providing a quick metric for ecologists, biologists, and students.
The operation is straightforward: the user inputs counts or proportions of each sampled species. The calculator computes the relative proportion (pi) of each species, squares it, sums these squares, and subtracts the result from 1. Mathematically, D = 1 - Σ(pi²). This index is sensitive to both richness (number of species) and evenness (distribution of abundances), being more influenced by the most common species.
Use this calculator in biodiversity studies, environmental monitoring, habitat comparisons, or ecological impact assessments. It is particularly useful when an intuitive measure of species dominance is desired. For instance, in a vegetation survey, Simpson's index can reveal whether an area is dominated by few species or exhibits high heterogeneity.
Important considerations: the index is sensitive to sample size, small samples may underestimate diversity. Also, it does not distinguish between loss of richness and reduction in evenness, so it is complementary to other indices like Shannon. Ensure that the data adequately represent the community and avoid comparing areas with very different sampling efforts.
Frequently asked questions
What does a Simpson index value of 0 mean?
It means there is only one species in the sample, indicating minimum diversity.
And a value of 1?
It indicates maximum diversity, with all species equally abundant in the sample.
Can I use this index to compare areas with different sample sizes?
It is not recommended, as the index is sensitive to sample size. Larger samples tend to capture more species, potentially inflating the value.
What is the difference between Simpson's index and Shannon's index?
Simpson gives more weight to common species, while Shannon is more sensitive to rare species. Both measure diversity but with different emphases.
What should I do if I have zeros in my species list?
Absent species (zero count) are not included in the calculation, as they do not contribute to diversity. Only input the species actually present in the sample.