3. Lecture-Species Richness, Diversity and Abundance

Species Richness

The number of different species present in a community.

Diversity

A measure that incorporates both species richness and abundance, reflecting the variety and distribution of species in a community.

Abundance

The total number of individuals of a species in a community.

Alpha (α)

The number of species in a specific local habitat.

Beta (β)

The turnover or change in species between different habitats.

Gamma (γ)

The total number of species in a larger region encompassing multiple habitats.

Beta Formula

Gamma= alpha*beta*# of habitats

Shannon-Weiner Index (H’)

A diversity index that accounts for both richness and evenness, calculated using the formula H’ = -Σ(pi ln pi).

Evenness

A measure of how evenly individuals are distributed among the different species in a community.

Dominance-Diversity Curves

Graphical representations that show the relative abundance of species in a community, indicating dominance by one or few species.

Species-Area Curve

A graphical representation showing the relationship between the area sampled and the number of species found, often used in conservation biology. (S= cA^z) S-# of species, A-area, C-a constant, z- slope of curve

Margalef’s Index

An index used to estimate species richness, calculated as Smarg = (S - 1)/ln(N).

Rarefaction

A method for estimating species richness by resampling data to account for differences in sampling effort.

Morisita Index of Similarity

A measure of similarity between two communities, taking into account the relative abundance of shared species, ranging from 0 to 1.

Species-Accumulation Curves

Graphs that show how species richness increases with sampling effort, typically leveling off as more species are found.

Evenness Index (E)

A measure derived from the Shannon-Weiner Index that indicates how evenly individuals are distributed among species, ranging from 0 to 1.

Field Data

Empirical data collected from specific locations, used for analysis in ecological studies.

Island Biogeography Theory

A theory that explains the number of species on islands based on area and distance from the mainland, relevant to species-area curves.