lecture 5: biodiversity

spatial grain

pixel size - increasing size will expect to see less variation

spatial extent

The total area or geographic scope over which data is collected or an ecological process occurs.

4 Diversity Metrics

Abundance, richness, evenness, composition

abundance

total number of individuals

richness

total number of species

evenness

relative similarity in abundance of species - how many individuals in each species

composition

identities of which species are present

Latitudinal Diversity Gradient (LDG)

generally higher richness near the equator and lower richness towards North/South pole - more diversity in the tropics

2 Ideas of Island Biogeography Theory

1. islands closer to a mainland get more immigration of species than farther islands

2. larger islands have lower extinction rates as there are more ways to survive

Species Area Relationship

larger habitats support more species due to increased opportunities for different species

Equilibrium Richness

In the context of island biogeography, this term refers to the stable number of species that an island can support.

Luxury Effect

when an abundance of resources (e.g., food, habitat) in an ecosystem allows for the presence of species that wouldn't otherwise thrive in a resource-limited environment.

5 Reasons for LDG

1. more land area supports more species

2. less stressful (warmer/wetter) environment in the tropics meaning more species can survive

3. more annual solar radiation = more energy, which can be shared among more species

4. higher temperature physically causes higher mutation and speciation rates

5. more time to evolve new species in the tropics (no ice sheets)