semelparous

Semelparity is a reproductive strategy in which an organism reproduces once and then dies or ceases reproduction. The term comes from Latin semel meaning once and parere to bear. In semelparous species energy is invested in a single, often large, reproductive event, after which survivors rarely reproduce again. This contrasts with iteroparity, in which individuals reproduce repeatedly over their lifespan.

Examples include many species of Pacific salmon (Oncorhynchus spp.) that undertake an arduous migration to spawn and then die, several monocarpic plants such as the agave and some bamboos that flower once and die, and certain insects like mayflies that have a brief adult life devoted to a single reproductive season.

Ecological and evolutionary factors favoring semelparity include episodic resource availability and selection for a synchronized, high-output reproductive effort when adult survival beyond the current season is uncertain. The costs of semelparity include reduced opportunities for subsequent reproduction and higher risk if the single reproductive episode fails. Semelparous species often rely on cues such as age, size, or environmental conditions to trigger the reproductive event, and in some groups the strategy is facultative, with individuals varying between semelparity and iteroparity depending on conditions. In plants, monocarpic species like agave flower once after reaching a threshold size and then die, whereas perennial species may be iteroparous. Understanding semelparity illuminates trade-offs between growth, reproduction, and survival in diverse life histories.