Whittaker’s alpha, beta, and gamma diversity are ways to describe biodiversity at different spatial scales. In simple terms, alpha is local diversity, beta is the difference between local communities, and gamma is the total diversity of a region.

The three levels

• Alpha diversity (α): species diversity within a single site, habitat, or community; often measured as species richness.
• Beta diversity (β): the turnover or dissimilarity in species composition between sites or communities.
• Gamma diversity (γ): the overall diversity of a larger region containing multiple sites or communities.

Whittaker’s idea

Whittaker introduced these terms to show how biodiversity changes across space, from a small local patch to an entire landscape or region. In his original multiplicative form, beta diversity can be expressed as $\beta =\gamma \mathrm{/}\alpha$β=γ/α.

If one forest plot has 10 species, that is its alpha diversity. If three nearby plots together contain 25 species total, that is the gamma diversity, and the amount of species change among plots is the beta diversity.

These measures help ecologists compare habitats, detect species turnover, and understand how biodiversity is distributed across landscapes. They are widely used in ecology, conservation planning, and biogeography.

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