Biological communities, species interactions and evolution

• Community• Species interactions• Community Dynamics• Succession: Primary and Secondary• Species composition & Distribution• Conservation Biology & Island

biogeography

Community• What is a community?• Chance assemblage of species?• Individualistic hypothesis• Interactive hypothesis• Continuous vs discrete boundaries

Ecological Niche

• Fundamental Niche

Potential niche with physical constraints

• Realized NicheActual niche with

biological constraints

Species InteractionsPredator-Prey relationships

Parasites

Keystone Predator

• Keystone species• Impact on community

structure• Maintain species

diversity• Examples• Pisaster (sea star)• Sea Otter

Kelp Forest

• Community structure• Sea urchin• Sea Otter

Symbiosis

• Commensalism• Mutualism

Competition

• Competitive exclusion Principle

• Avoidance• Resource partitioning

Community Dynamics

• Changes over time• Change in species #• Change in species

composition

Succession:• Two types:• Primary• Secondary• Pioneer

species:mosses• Species can facilitate/or

inhibit the entry of other species into the community

• Can reach a climax community

Succession: Secondary

• Existing communities have been cleared

• Soil present• Volcanic explosion• Farming• Fire

Succession: Secondary

Succession: Secondary

• Periodic disturbance

• Disclimaxcommunities: fire/ herbivores

• Community Senescence

Community Characteristics

• Species richness# of species

• Species abundance# present in each

species• Biodiversity

Biodiversity: Rare vs Common Spp

Threat of introduced species