Beta Diversity Calculator

Beta diversity measures the change in species composition between two or more habitats or ecosystems. It quantifies how many species are unique to each site versus how many are shared, reflecting the degree of species turnover across environments. A higher beta diversity means the two sites share fewer species and are more ecologically distinct.

Whittaker's beta diversity (β) is calculated as β = (S1 − c) + (S2 − c), where S1 is the number of species in Site 1, S2 is the number of species in Site 2, and c is the number of species shared between both sites. The result represents the total number of species not found in both environments combined. Some formulations also express it as β = γ / ᾱ − 1, where γ is total species richness and ᾱ is mean alpha diversity.

Both indices measure similarity between two communities, but they weight shared species differently. The Jaccard Index is calculated as c / (S1 + S2 − c) and treats each species presence equally. The Sørensen Index is 2c / (S1 + S2) and gives more weight to shared species, making it more sensitive to common species. For dissimilarity (beta diversity), you subtract each similarity index from 1.

A high beta diversity value indicates a low level of similarity between the two sites — most species in one habitat are not found in the other. This suggests significant species turnover, which can be due to differences in geography, climate, soil type, or disturbance history. Conversely, a low beta diversity indicates the two environments share most of their species and are ecologically similar.

Alpha (α) diversity refers to species richness within a single habitat or site. Beta (β) diversity measures the difference or turnover in species composition between two or more habitats. Gamma (γ) diversity is the total species richness across all sites combined in a landscape. Together, alpha and beta diversity determine gamma diversity: γ = ᾱ × (β + 1) in Whittaker's framework.

No. The number of shared species (c) cannot exceed the smaller of S1 or S2, since you cannot share more species than either site contains. This calculator will flag an error if shared species is greater than either site's species count. Always verify your data entry to ensure logical consistency.

Beta diversity is widely used in ecology, conservation biology, and microbiome research. Ecologists use it to assess habitat fragmentation, monitor biodiversity across landscapes, and evaluate the effectiveness of conservation areas. In microbiome studies, beta diversity metrics like Bray-Curtis or Jaccard dissimilarity are used to compare microbial communities between patients, environments, or treatment groups.

There is no universal 'good' value — interpretation depends entirely on context. For Sørensen and Jaccard similarity, values above 0.5 generally indicate moderate to high similarity. Whittaker's raw beta has no fixed scale and depends on the magnitude of species richness. Researchers typically compare beta diversity values across multiple site pairs or use rarefaction and permutation tests to assess statistical significance.