Berger-Parker Dominance Index

Understanding the Berger-Parker Dominance Index (d)

The Berger-Parker Index (d) is a simple measure of species dominance within an ecological community. It quantifies the proportional abundance of the most abundant species.

Formula:

d = Nmax / N

• Nmax is the number of individuals in the most abundant species.
• N is the Total Number of Individuals of all species in the sample.

Interpretation:

• The Berger-Parker Index (d) ranges from nearly 0 to 1.
• A value close to 1 indicates that one species strongly dominates the community.
• A value close to 0 (or more precisely, close to 1/S where S is species richness) indicates that the most abundant species is not overwhelmingly dominant, suggesting a more even distribution of individuals among species (though it doesn't directly measure evenness across all species).
• Higher values of 'd' mean lower diversity in terms of dominance.

Reciprocal Berger-Parker Index (1/d):

1/d = N / Nmax

• This form is sometimes used as a simple diversity measure. Higher values of 1/d indicate higher diversity (less dominance).
• It represents how many equally common species would produce the same d.

Advantages and Disadvantages:

• Advantage: Very easy to calculate and interpret.
• Disadvantage: It only considers the most abundant species and ignores the relative abundances of other species and overall species richness. Therefore, two communities could have the same Berger-Parker index but very different overall diversity structures.

How to Use:

1. Enter the number of individuals (count) for each species identified in your sample.
2. Use the "Add Species" button to create more input rows as needed.
3. Click "Calculate Index" to see the Berger-Parker Dominance Index and related values.