postzygotic reproductive isolating mechanism

biology

Also known as: postzygotic RIM

Written by

The Information Architects of Encyclopaedia Britannica

Last updated

July 1, 2026

Quick Summary

Postzygotic reproductive isolating mechanisms (RIMs) are biological factors that prevent different species from successfully interbreeding after fertilization has occurred. These mechanisms reduce the viability or fertility of hybrid offspring.123

There are three main types of postzygotic RIMs:
* Hybrid inviability: Hybrid zygotes fail to develop into mature individuals, often dying during early developmental stages.2
* Hybrid sterility: Hybrid offspring develop into adults but are unable to produce functional gametes, making them sterile (e.g., mules).1
* Hybrid breakdown: Hybrids may be vigorous and fertile, but their subsequent generations are poorly viable or sterile.3

These mechanisms are crucial in maintaining the distinctness of species.4

Summary created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

4 Britannica Sources

Ask Britannica AI about this topic

Britannica doesn't have a full article on this topic, so we've curated a list of our relevant coverage.

evolution
Reproductive isolation
…take effect before fertilization, and postzygotic, those that take effect afterward. Prezygotic RIMs prevent the formation of hybrids between members of different populations through ecological, temporal, ethological (behavioral), mechanical, and gametic isolation. Postzygotic RIMs reduce the viability or fertility of hybrids or their progeny.
Read More
…take effect before fertilization, and postzygotic, those that take effect afterward. Prezygotic RIMs prevent the formation of hybrids between members of different populations through ecological, temporal, ethological (behavioral), mechanical, and gametic isolation. Postzygotic RIMs reduce the viability or fertility of hybrids or their progeny.
Read More