Simpson Diversity Index Calculator

Calculate the Simpson Diversity Index to assess species diversity in a community. This calculator helps determine how diverse a community is by measuring the probability that two randomly selected individuals belong to the same species.

Input Parameters

Calculation Results

Calculation Formula

D = 1 - Σ(n_i(n_i-1)/N(N-1))

Where:
D = Simpson Diversity Index (0 to 1, higher means more diversity)
n_i = number of individuals in species i
N = total number of individuals in the community

Results

Simpson Index (D):

-

Inverse Simpson Index (1-D):

-

Mean pairwise similarity:

-

Effective number of species (SES):

-

Simpson Diversity Index Calculator Calculator Usage Guide

Learn how to use the Simpson Diversity Index Calculator and understand its ecological significance

What is the Simpson Diversity Index?

The Simpson Diversity Index (SDI) is a measure of biodiversity that takes into account the number of species in a community and the relative abundance of each species. It provides a way to quantify the diversity of a community by measuring the probability that two randomly selected individuals belong to the same species.

How to Use This Calculator

  1. Enter the number of species in your community.
  2. For each species, enter the number of individuals.
  3. Click the "Calculate" button to compute the Simpson Diversity Index.
  4. The calculator will display the Simpson Index (D), which ranges from 0 to 1, where higher values indicate greater diversity.

Interpreting the Results

  • Simpson Index (D): A value of 0 indicates no diversity (all individuals belong to the same species), while a value of 1 indicates maximum diversity (all species have equal abundance).
  • Inverse Simpson Index (1-D): This represents the probability that two randomly selected individuals belong to different species.
  • Mean Pairwise Similarity: The average proportion of individuals that are the same when compared pairwise.
  • Effective Number of Species (SES): Represents the number of equally abundant species that would produce the same level of diversity as observed in the community.

Ecological Significance

The Simpson Diversity Index is widely used in ecology to compare biodiversity across different habitats or over time. It helps ecologists understand community structure and assess the impact of environmental changes on species diversity.

Example Application

Imagine you are studying two forest plots. Plot A has 100 trees consisting of 50 oak trees and 50 maple trees. Plot B has 100 trees consisting of 100 maple trees.

For Plot A: SDI = 1 - [(50/100 × 49/99) + (50/100 × 49/99)] = 0.75

For Plot B: SDI = 1 - [(100/100 × 99/99)] = 0

This indicates that Plot A has greater biodiversity than Plot B.