0.3429
0.6571
34.29
%
38
32
23
24
0.3429
0.6571
34.29
%
38
32
23
24
The Bray-Curtis Dissimilarity Calculator measures the compositional dissimilarity between two ecological communities based on species abundance data. Unlike the Jaccard and Sorensen indices which use presence-absence data only, the Bray-Curtis index incorporates abundance information, making it more sensitive to changes in community structure.
This simplified calculator uses three species. The Bray-Curtis index ranges from 0 (identical communities) to 1 (completely different). It is the most widely used abundance-based dissimilarity measure in community ecology and is a standard metric in multivariate ecological analyses.
The Bray-Curtis Dissimilarity is calculated as:
BC = 1 - (2 × Σmin(ai, bi) / (Σai + Σbi))
Where:
The sum of minimums represents the shared abundance. Dividing by total abundance and subtracting from 1 gives the dissimilarity. BC = 0 means identical abundance profiles; BC = 1 means no shared species.
Inputs
Results
Min sums: min(10,15)+min(20,5)+min(8,12) = 10+5+8 = 23. Totals: 38+32 = 70. BC = 1 - 46/70 = 0.229.
Inputs
Results
Min sums: 2+1+0 = 3. Totals: 80+43 = 123. BC = 1 - 6/123 = 0.951. These sites are very different.
Bray-Curtis incorporates species abundance data, not just presence-absence. This makes it sensitive to changes in relative abundance even when the same species are present. Two sites may share all species but differ greatly in their abundance distributions, which Bray-Curtis will detect but Jaccard and Sorensen will not.
No, the Bray-Curtis dissimilarity does not satisfy the triangle inequality, so it is technically a semi-metric. However, it is still widely used in ecological ordination (like NMDS) and clustering because it produces ecologically meaningful results and handles zero-abundance data well.
A Bray-Curtis value of 0.5 means the two sites share 50% of their total abundance in common. Half of the combined abundance is shared, and half differs between sites. This represents moderate dissimilarity in community composition.
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