Methods of determining the diversity of species
Species richness. This is the number of different species in an ecosystem. It takes no notice of abundance and gives as much weight to those species which have very few individuals as to those who have thousands.
Species evenness. This is a measure of the relative abundance of the different species. A community dominated by one or two species is considered to be less diverse than one in which several different species have a similar abundance.
Percentage cover. If we want to know what kind of plants are in a particular habitat, and how many there are of each species, it is usually impossible to go and count each and every one present. Therefore, we use a quadrat and estimate percentage cover.
Percentage frequency. This is the probability that a species will be found within a single quadrat.
Percentage frequency = (number of quadrats in which the species is found/total number of quadrats) x 100
Simpsons Diversity Index (D). This measures the probability that two individuals randomly selected from a sample will belong to the same species. If you need extra help on calculating this, then head to the Simpsons Diversity page.
∑ = sum of
n = number of individuals
N = total number of individuals
The value of Simpsons Diversity Index ranges between 0 and 1. What does an index closer to 1 represent?
What are some problems associated with the percentage cover method of determining species diversity?