Enter the number of individuals in each species (comma-separated):
Total number of individuals (N):
Simpson’s Dominance Index (D):
The Dominance Index Calculator is a tool used in ecology and biodiversity studies to measure species dominance within a given ecosystem. This calculation helps researchers understand how evenly individuals are distributed among species and identify which species dominate a community. A higher dominance index indicates that a few species are more prevalent, while a lower index suggests a more even distribution of species.
Formula of Dominance Index Calculator
The Dominance Index can be calculated using Simpson’s Dominance Index formula:
Where:
- D = Simpson’s dominance index
- ni = Number of individuals in the ith species
- N = Total number of individuals in the sample
Alternative Formula:
D = Σ(pi²)Where:
- pi = Proportion of individuals belonging to the ith species (ni/N)
The value of D ranges between 0 and 1. A value closer to 1 indicates high dominance by a few species, while a value closer to 0 suggests a more balanced distribution among species.
General Terms and Conversion Table
Here is a quick reference table showing dominance index values under different species distributions:
| Number of Species | Total Individuals | Dominance Index (D) |
|---|---|---|
| 2 | 50 | 0.75 |
| 3 | 75 | 0.60 |
| 5 | 100 | 0.40 |
| 10 | 200 | 0.20 |
| 20 | 500 | 0.10 |
Example of Dominance Index Calculator
Suppose you are studying a forest ecosystem with 3 species:
- Species A: 40 individuals
- Species B: 30 individuals
- Species C: 30 individuals
Total individuals (N) = 40 + 30 + 30 = 100
Using the formula:
D = [(40(40-1)) + (30(30-1)) + (30(30-1))] / [100(100-1)]
D = [(40*39) + (30*29) + (30*29)] / (100*99)
= (1560 + 870 + 870) / 9900 = 0.36So, the dominance index for this ecosystem is 0.36, indicating a moderately balanced species distribution.
Most Common FAQs
The Dominance Index helps ecologists assess biodiversity and understand how a few species may dominate an ecosystem. This is useful in conservation efforts and ecological balance studies.
A high dominance index (close to 1) means that one or a few species dominate the community, reducing overall biodiversity.
Yes, the dominance index can be apply in economics, sociology, and other fields to measure the dominance of certain groups within a system.