propagule

Propagule is a biological term for any unit of reproduction or dispersal that can give rise to a new individual or colony. The concept encompasses not only seeds and spores but also vegetative or fragmentary forms capable of initiating growth into a new plant, fungal mycelium, or colonial organism. The propagule is a key element in how organisms spread, persist, and colonize new environments.

Common examples of propagules include seeds and spores, as well as vegetative propagules such as cuttings, offsets, bulbs, tubers, rhizomes, and gemmae. In addition, many organisms produce specialized propagules for dispersal—for instance, fragments of coral or bryozoan colonies, lichenia soredia or isidia, and other structures that can establish a new individual when dispersed. In fungi, spores are the primary propagules; in plants, both sexual (seeds, spores in non-vascular plants) and asexual (cuttings, tubers) propagules are important.

Propagule pressure, a concept used in ecology and invasion biology, refers to the number, viability, and timing of propagules entering a region. Higher propagule pressure generally increases the likelihood of establishment and spread, influencing management and restoration strategies. Dispersal mechanisms are varied and include wind, water, animal handlers, and human activities.

Understanding propagules informs fields from agriculture and horticulture to conservation and ecosystem restoration, where propagule size, nutrition, and genetic diversity influence the success of propagation and establishment in new sites.