Ch. 16 - Species abundance & diversity

Community

Different species that inhabit a defined area

Guild

Group of organisms that make their living in a similar way (ex. birds that live and feed in a specific part of a tree canopy)

Life-form

Classification of structure and growth dynamic of plants

Relative abundance

proportion of a particular species relative to other species in a community.

Preston’s Distribution of Commonness and Rarity

Species diversity is based on two factors:

Species richness & Species evenness 

Species richness

the number of different species in a given area.

Species evenness

relative abundance of species in a community.

Shannon Weiner Diversity Index

Method for quantifying species diversity that considers both species richness and species evenness.

Rank Abundance Curve

plot of relative species abundance against rank in abundance.

Based on rank abundance curve how can you tell which community has greater species evenness?

a lower slope will have greater species evenness.

Calculating species diversity is important because …..

Environmental complexity creates more

Species diversity

Equilibrium

State of community/ecosystem when environmental conditions remain reasonably stable.

Disturbance

Any event that removes all or part of a community.

Potential sources of disturbance:

• abiotic

• biotic

• human-caused

Intermediate Disturbance Hypothesis 

Predicts that intermediate levels of disturbance promote higher levels of species diversity. 

How does disturbance frequency affect species diveristy?

Low levels of disturbance = more reduced diversity because of competition

High levels of disturbance reduced diversity

• in the middle is ideal for diversity

Urban Ecology

Study of ecology in urban settings