Heteroecious life cycle

Definition

A life cycle in which a parasite or herbivore obligately alternates between two phylogenetically unrelated host species to complete development and reproduction, typically involving distinct morphological forms or reproductive modes on each host.

Etymology

From Greek heteros (other, different) + oikos (house, dwelling), referring to the use of multiple host 'homes'.

Example

The woolly apple aphid (Eriosoma lanigerum) exhibits a heteroecious life cycle: sexual generations and egg-laying occur on American elm (Ulmus), while multiple parthenogenetic generations feed on apple roots and shoots (Malus); neither host alone supports the full cycle.

Synonyms

• Heteroxenous life cycle
• Host-alternating life cycle

Related Terms

• autoecious life cycle
• Holocyclic
• Anholocyclic
• parthenogenesis
• Host race
• Gall aphid
• Rust fungus

Usage Notes

Primarily used for aphids (Aphididae) and rust fungi (Pucciniaceae), where the phenomenon is well-documented. Contrast with autoecious (single-host) cycles. Not all host-switching qualifies: true heteroecy requires obligate alternation with specific, evolutionarily conserved host pairs. Some authors restrict 'heteroecious' to aphids and use 'heteroxenous' more broadly for other parasites.