Community Ecology
Community ecology studies the assemblages of interacting species that occupy a place, asking what determines their composition, diversity, and structure and how interactions among them organise the whole.
Definition
Community ecology is the study of the composition, diversity, structure, and dynamics of assemblages of co-occurring, interacting species, and of the processes that assemble and maintain them.
Scope
This area treats multispecies assemblages: patterns of species richness, evenness, and diversity and how they are measured; the assembly and temporal change of communities through succession; the architecture of food webs and the flow of energy through trophic levels; and positive interactions such as mutualism and symbiosis. It encompasses competing explanations of community structure, from niche-based to neutral, and the role of keystone species and trophic cascades.
Sub-topics
Core questions
- What determines the number and relative abundance of species in a community?
- How do communities assemble and change over time?
- How is energy transferred through food webs and trophic levels?
- How do interactions such as competition, predation, and mutualism structure communities?
Key theories
- Niche versus neutral assembly
- Communities may be structured by species' differing niches and deterministic interactions, or, under neutral theory, by stochastic birth, death, dispersal, and speciation among ecologically equivalent individuals; both perspectives explain aspects of observed diversity patterns.
- Keystone species and trophic cascades
- Some species exert effects on community structure far out of proportion to their abundance, and removing top consumers can cascade down food webs to reorganise diversity and the abundance of lower trophic levels.
Clinical relevance
Community ecology informs the conservation of biodiversity, the restoration of degraded habitats, the prediction of invasion and extinction effects, and the management of ecosystems where the loss of key species can restructure entire assemblages. This is educational context, not management prescription.
History
Early debate pitted Clements's view of the community as a tightly integrated superorganism against Gleason's individualistic concept. Mid-century work by MacArthur, Hutchinson, and others quantified diversity and niche relations, Paine's keystone-species experiments transformed the field in the 1960s, and Hubbell's neutral theory reopened the question of how diversity is maintained in 2001.
Debates
- Are communities integrated units or chance assemblages?
- The Clementsian view of communities as tightly co-evolved superorganisms contrasts with the Gleasonian individualistic view that assemblages are loose, chance collections of species with overlapping tolerances; modern ecology leans toward the individualistic end while recognising strong interactions.
Key figures
- Robert MacArthur
- Robert Paine
- Joseph Connell
- Stephen Hubbell
- Henry Gleason
Related topics
Seminal works
- begon2006
- morin2011
- paine1966
Frequently asked questions
- What is an ecological community?
- An ecological community is the set of populations of different species that occur together in a place and potentially interact, considered as a unit of study above the population level.
- What is a keystone species?
- A keystone species has a disproportionately large effect on its community relative to its abundance, so that its removal causes major changes in the diversity and structure of the assemblage.