Simpsons Diversity Index To measure the diversity in

Simpson’s Diversity Index To measure the diversity in an ecosystem

Simpson’s Diversity Index �Attempts to quantify the diversity (variety) of an ecosystem. �There are two components: Evenness Richness

Evenness �Evenness is a measure of the relative abundance of the different species within an area. �When the numbers of each type of species is even, the value for the Simpson Diversity Index will be larger.

Species richness �Richness is a measure of the variety of the species �More species is “richer” so the value for the index will be higher.

The equation D = N(N - 1) n(n -1) D = diversity index N = total number of organisms of all species found n = number of individuals of a particular species

The Simpson Diversity Index �A high value of D suggests a stable and ancient site �A low value of D could suggest pollution, recent colonization or agricultural management. � The value of D indicates the richness and evenness of the species found within the area sampled.

Predict the value for D for the following: (high or low) �Tropical rainforest �Desert �A wheat field �A polluted river �A tall grass prairie

How to Calculate D: D = N(N – 1) n(n -1) 1. 2. 3. 4. Record the numbers of each species Calculate n-1 for each species Find the total number of organisms, N Calculate the Simpson Diversity Index

Values for D �What is the lowest possible value? �What does a higher value indicate?

The values for D �The lowest possible value is 1. When there is only one kind of species. �This is a monoculture or an area that has been disturbed by pollution, a flood, or another big event �A high value for D indicates stability, complexity and an older ecosystem.

Calculate the Simpson’s Diversity Index for each sample Comment on the evenness and richness of each sample.

Answers �Sample One: 2. 99 �Sample Two: 1. 15 �Both have the same richness as there are three species in each area. �Sample One is more diverse because the species are more even.