What are alpha, beta, and gamma diversity?

Alpha diversity refers to the average species diversity in a habitat or specific area. Alpha diversity is a local measure.

Beta diversity refers to the ratio between local or alpha diversity and regional diversity. This is the diversity of species between two habitats or regions. It is calculated by the following equation:

(number species in habitat 1- number of species habitat 2&1 have in common)+(number of sp in H2- number of sp H1&2 have in common)

Gamma diversity is the total diversity of a landscape and is a combination of both alpha and beta diversity.

In the image below, assume the different colors represent different species of fish. The alpha diversity of Site A is 3 because there are three different species at Site A. The beta diversity of sites A and B is 2 because there are two species (the red one at site B and the teal one at site A) that are distinct from one another. The gamma diversity for the whole ecosystem is 5 because there are five different species of fish (black, orange, green, red, and purple with black stripes).