Allogenic succession

Definition

Ecological succession driven by external abiotic forces rather than by the biotic community itself. These disturbances originate outside the ecosystem and alter physical conditions—substrate, hydrology, temperature, or chemical environment—such that existing assemblages are displaced and new colonization sequences begin. In entomological contexts, allogenic drivers include flooding that inundates riparian beetle communities, volcanic ash deposition that resets pollinator habitat, or drought-induced salinization that eliminates halophilic insect assemblages.

Etymology

Greek allos (other, different) + -genic (producing), from the contrast with autogenic (self-producing) succession; ecological usage established by early 20th-century plant ecologists

Example

Following a 500-year flood that scoured cobble bars along a Montana river, the allogenic succession of riparian vegetation triggered a parallel arthropod succession: ground beetles (Carabidae) with high dispersal capacity colonized within weeks, while flightless springtails and oribatid mites required months to arrive via downstream drift and aerial deposition.

Synonyms

• allogenic sere

Related Terms

• Autogenic succession
• primary succession
• secondary succession
• disturbance regime
• ecological resilience
• habitat heterogeneity
• chronosequence

Usage Notes

The allogenic/autogenic distinction is relative and scale-dependent. A disturbance is allogenic if its driver lies outside the defined ecosystem boundary; the same event may be autogenic at broader scales. In insect ecology, allogenic succession is particularly relevant for understanding community assembly in floodplains, fire-prone landscapes, and coastal systems where physical forcing dominates over internal biotic feedbacks.