Biodiversity Simpson Index Calculator
Calculate the Simpson Diversity Index from species counts to measure the biodiversity of an ecosystem sample.
Simpson Diversity (1-D)
0.7222
Simpson Diversity (1-D) vs Species A Count
公式
## Simpson Diversity Index The Simpson Index measures the probability that two randomly selected individuals belong to different species. Higher values mean greater diversity. ### Formula **D = Sum of [n(n-1)] / [N(N-1)]** Where n is the count of each species and N is the total count. D ranges from 0 to 1, where 0 is infinite diversity and 1 is no diversity. The complement (1-D) is more intuitive: higher values mean more diversity.
计算示例
A forest plot has 40 oaks, 25 maples, 20 birches, and 15 pines.
- 01Total N = 40 + 25 + 20 + 15 = 100
- 02Sum n(n-1) = 40x39 + 25x24 + 20x19 + 15x14 = 1560 + 600 + 380 + 210 = 2750
- 03D = 2750 / (100 x 99) = 2750 / 9900 = 0.2778
- 04Diversity (1-D) = 1 - 0.2778 = 0.7222
- 05Reciprocal = 1/0.2778 = 3.60
常见问题
What does a Simpson Index of 0.72 mean?
A 1-D value of 0.72 means there is a 72% chance that two randomly picked individuals will be from different species. This indicates moderate to good diversity.
How many species can this handle?
The formula works for any number of species. This calculator uses four inputs for simplicity, but the principle extends to dozens or hundreds of species.
Simpson vs Shannon index?
Simpson is more sensitive to dominant species, while Shannon gives more weight to rare species. Simpson is also easier to interpret as a probability.