Patterns in Biodiversity

Community

A group of interacting species that occur together at the same time and place.

Species Interactions

The relationships among species and their physical environment that define community character and function.

Species Diversity

A measure that combines species richness (number of species) and species evenness (abundance comparison).

Species Richness

The count of different species in a community.

Species Evenness

The variation in abundance among species in a community.

Sudden Oak Death

A disease caused by Phytophthora ramorum, first reported in 1995, affecting oak trees.

Rank-Abundance Diagram (RAD)

A graphical representation showing the abundance of species in a community, typically with a ‘lazy J’ shape.

Rabinowitz ‘Rarity’ Criteria

Criteria that assess species rarity based on geographic area, habitat specificity, and local population density.

Diversity Indices

Quantitative measures that incorporate species richness and abundance to assess community diversity.

Species Accumulation Curve

A graph showing the relationship between the number of species and sampling effort, which eventually flattens.

Chao1 Estimator

A method for estimating the number of undiscovered species using the ratio of singletons to doubletons.

Species-Abundance Distribution (SAD)

A frequency distribution that describes the commonness and rarity of species in a community.

Neutral Theory

A theory that assumes all individuals within a trophic level have equal chances of reproduction and death, regardless of species identity.

MacArthur’s ‘Broken Stick’ Model

A mathematical model representing the random division of a resource into sections.

Simpson’s Diversity Index

A measure of community diversity that considers both species richness and abundance patterns.

Shannon Index

A measure of community diversity that accounts for both abundance and species richness patterns.

Hill Numbers

A method for quantifying species diversity, extended to include phylogenetic and functional diversity.

γ-Richness

The total species richness of a region.

α-Richness

The average species richness within habitat patches.

β-Richness

The between-patch component of regional richness, indicating species distribution heterogeneity.

Phase 1 Habitat Survey

A standard system for classifying and mapping wildlife habitats in the UK.

Phytosociology

The study of plant communities and their floristic composition.

Succession

The developmental process of vegetation leading to a stable climax community.