Community Ecology

Vocabulary:

• Community: Interacting species inhabiting an area

• Community structure: Properties include number of species, relative abundances, and kinds of species

• Guild: Group of organisms that exploit the same resource in similar ways (e.g. all kinds of fish in a community that eat leaf litter), can consist of different species, typically categorized by what they eat

• Food chain: Abstract representation of feeding relationships within a community, just one to another

• Food web: Many intertwining food chains, includes predation, parasitism, competition, and mutualism

• Dominant/foundation species: Species with substantial influence on community structure, due to the fact that there are a lot of them, or a few very large ones. They have a high biomass

• Keystone species: A species with a disproportionate impact on the community relative to its abundance, could be a dominant species or not. Has a low density but large impact. Removal of this species initiates changes in community structure and could result in significant diversity loss (e.g. African Elephants create tree limbs as they knock over trees to eat, other species like arboreal geckos love these areas and live there)

• Trophic level: Feeding groups of organisms, determined by where energy is derived from. The amount of energy transferred between levels is 10%

  • Primary producer: Plants/phytoplankton that make their own energy

  • Primary consumer: Herbivores, eat primary producers

  • Secondary consumer: Eat primary consumers

  • Tertiary consumer: Eat secondary consumers

  • Quaternary consumer: Eat tertiary consumers. context dependent, hard to separate from tertiary

• Top-down control of productivity: Community control, where carnivores depress herbivore populations that would otherwise consume most of the vegetation (e.g. wolves in Yellowstone depressing populations of primary consumers, allowing for more primary producers)

• Bottom-up control of productivity: Community control, where abundances of organisms in a trophic level is determined by the rate of food production for them to eat, more primary producers means more primary consumers

• Trophic cascade: When the removal of one trophic level species effects others below it proportionately

Factors that influence community structure:

• Biological: Looks at total diversity, how biotic factors exist and interact

  • Relative abundance

  • Species richness

  • Species interactions

• Physical: What resources are there, abiotic factors

  • Habitat (soil/climate)

  • Adjacent landscapes