Density dependence

Definition

In population ecology, the regulation of per capita population growth rates by the density of individuals, such that growth slows as density increases and accelerates as density decreases. This feedback mechanism arises from resource limitation, competition, predation, disease transmission, or other biotic factors whose per capita effects intensify with crowding.

Etymology

Example

In outbreak populations of the desert locust (Schistocerca gregaria), density-dependent cannibalism intensifies as nymphal bands become denser, eventually suppressing survival rates and contributing to population collapse; conversely, at low densities, reduced competition and cannibalism permit exponential growth.

Synonyms

• density-dependent regulation
• negative density dependence

Related Terms

• density independence
• Carrying capacity
• Allee effect
• K-selection
• Population regulation
• Intraspecific competition
• logistic growth

Usage Notes

Distinguish from density independence, where environmental factors (weather, catastrophes) affect populations regardless of density. Density dependence can be positive (Allee effect) at very low densities, though the term is most often used for negative feedback. In entomology, density dependence is critical for predicting pest outbreaks and designing biological control; parasitoid attack rates often show delayed density dependence, creating population cycles.