Berger-Parker Dominance Index Calculator

The Berger-Parker Dominance Index (d) measures the proportional abundance of the most dominant species in a sample. It is calculated as d = N-max / N, where N-max is the number of individuals in the most abundant species and N is the total number of individuals across all species. Values range from 0 to 1, with higher values indicating greater dominance.

Divide the count of the most abundant species (N-max) by the total number of individuals in the sample (N). For example, if the most abundant species has 150 individuals and the total sample size is 300, then d = 150/300 = 0.5. A value of 0.5 means the dominant species makes up 50% of the community.

A high Berger-Parker Index (close to 1) indicates that a single species dominates the community, suggesting low diversity. A low value (close to 0) indicates that no single species is overwhelmingly dominant, which typically reflects a more diverse and evenly distributed community.

The inverse index (1/d) is the reciprocal of the Berger-Parker Index. It represents how many times the most dominant species would need to be replicated to fill the entire sample. A higher inverse index indicates greater diversity, since the dominant species is a smaller fraction of the total community.

The Berger-Parker Index only considers the single most abundant species, making it sensitive to dominance at the top. Simpson's Index, by contrast, accounts for the probabilities of all species, weighing common species more heavily. The Berger-Parker Index is simpler but can be less informative in communities with several highly abundant species.

In highly diverse ecosystems like tropical rainforests, values tend to be low (0.05–0.20). In disturbed or stressed habitats with a single dominant species, values can exceed 0.80. Values around 0.3–0.5 are common in moderately diverse communities such as temperate forests or grasslands.

Yes. The Berger-Parker Index is widely used in microbial ecology and metagenomic studies for OTU abundance data. Simply enter the read counts or sequence counts for each OTU as your species counts, and the calculator will return the dominance index just as tools like mothur's summary.single command would.

You need at least 2 species (categories) for the index to be meaningful. With only one species, d would equal 1 by definition. In practice, the index becomes most informative when you have 5 or more species, as it better captures the contrast between the dominant species and the rest of the community.