Communities

Ecological niche

• Multidimensional phase space defined by a species' resource requirements
• Condition actually constraining population size is the limiting factor (less than needed or more than tolerated)
• Niche that a species could theoretically occupy is its fundamental niche
• Actually occupied niche is the realized niche
• Are communities dominated by niche-assembly or dispersal-assembly rules?

Keystone species

• Species that significantly affects the rest of the community in disproportion to its relative abundance
• e.g. Wolves in Yellowstone Park, Sea Otter, Grizzly Bear, Beaver