Aggregation

Definition

A non-random spatial clustering of individuals of the same species, typically arising from behavioral responses to resources, conspecifics, or environmental cues rather than from resource patchiness alone. Distinguished from aggregation of resources or random distribution; emphasizes the active behavioral component of group formation.

Etymology

Latin aggregare, to collect into a flock or herd (ad-, toward + grex, flock)

Example

Carrion beetles (Silphidae) form aggregations at vertebrate carcasses through pheromone-mediated attraction, with arrival of initial individuals releasing volatiles that recruit conspecifics and facilitate cooperative resource defense.

Synonyms

• clumping
• grouping

Related Terms

• Dispersion
• overdispersion
• underdispersion
• swarming
• Lek
• quorum sensing
• conspecific attraction
• Allee effect

Usage Notes

In ecology, 'aggregation' specifically denotes clumped distributions with a behavioral mechanism; purely passive accumulation due to heterogeneous resources is often termed 'contagious distribution' or 'patchiness.' The term carries no implication of social cooperation—aggregations may involve mutual attraction with subsequent competition (e.g., fruit flies on rotting fruit) or true cooperative benefits (e.g., thermoregulatory clustering in overwintering ladybird beetles). Contrast with 'overdispersion' (uniform spacing, often territorial) and 'random distribution' (Poisson expectation). In population genetics, 'Wahlund effect' describes artifactual homozygote excess from unrecognized aggregation structure.