Beta diversity

Beta diversity (β-diversity) is a measure of biodiversity which works by comparing the species diversity between ecosystems or along environmental gradients. This involves comparing the number of taxa that are unique to each of the ecosystems.

It is the rate of change in species composition across habitats or among communities. It gives a quantitative measure of diversity of communities that experience changing environments.See alpha diversity, gamma diversity, global diversity.

Indices

* Sørensen's similarity indexSørensen, T.A. (1948) A method of establishing groups of equal amplitude in plant sociology based on similarity of species content, and its application to analyses of the vegetation on Danish commons. Kongelige Danske Videnskabernes Selskabs Biologiske Skrifter, 5, 1–34.] $$eta=frac{2c}{S_1+S_2}

where, S₁= the total number of species recorded in the first community, S₂= the total number of species recorded in the second community, and c= the number of species common to both communities. The Sørensen index is a very simple measure of beta diversity, ranging from a value of 0 where there is no species overlap between the communities, to a value of 1 when exactly the same species are found in both communities.

* Whittaker's measure [Whittaker, R.H. (1960) Vegetation of the Siskiyou mountains, Oregon and California. Ecological Monographs, 30, 279–338.] $$eta=frac{S}{ar alpha} or eta=frac{S}{ar alpha}-1

where, S= the total number of species recorded in both communities, $$ar alpha=average number of species found within the communities.

References