Aquatic ecology and Biodiversity

Unit 4- Community ecology

4.1.12. Influence of evenness of species diversity
Species diversity is also influenced by the relative abundance of individuals in the species found in a community. Evenness measures the variation in the abundance of individuals per species within a community. Communities with less variation in the relative abundance of species are considered to be more “even” than a community with more variation in relative abundance. Consider the following two communities.
All five species in Community A have the same abundance, whereas there is great variation in abundance across the five species in Community B. For this reason, we would consider Community A to be more even.


All else being equal, communities with greater evenness are considered to have greater species diversity. Even though species richness of the two communities is equal (species richness = 5 in each community), Community B is less diverse than Community A because most of the individuals in Community B are members of the same species.