Reproductive Isolation Ontology
Understanding reproductive isolation between lineages is a central goal of speciation research. Although estimates of reproductive isolation have now been made across a wide range of taxa, comparing and synthesising these data remains difficult because the field lacks a shared language for classifying and reporting them.
The Reproductive Isolation Ontology (RIO) was developed to help address this challenge.
Beginning in 2021, we collated reproductive isolation estimates from case studies spanning many different clades, with the aim of understanding how reproductive isolation evolves across the Tree of Life. During this process, we identified several recurring challenges in classifying individual estimates of reproductive isolation. In particular, a useful framework must be able to accommodate:
- the diversity of organismal life histories
- the different resolutions at which reproductive isolation is measured
- the complexity of postzygotic isolation
- the multiple dimensions along which reproductive isolation can be quantified
Building on previous classification schemes, we developed RIO as a standardised framework for describing, classifying, and organising estimates of reproductive isolation.
A full description of the ontology, including its aims, structure, and advantages, is provided in our paper: Walker et al. 2026. A standardised framework for classifying estimates of reproductive isolation. Evolution Letters.
How can I use the RIO?
We strongly encourage speciation researchers to classify their estimates of RI using the RIO when publishing them. For that reason, we provide a guide to doing this (including a dictionary of all terms and worked examples) and a user-guided decision tree. Please do cite the article above when using the RIO.
The RIO will be updated over time as it is used and tested. Below you can find a versioned archive of the RIO. Please check back regularly for updates, new editions, and guidance on applying RIO to reproductive isolation data.
• RIO v1.0 guide (current version, supplementary material of Walker et al. 2026)
• RIO decision tree for aiding classification: [work in progress, check back later!]
Questions and suggestions
We warmly welcome and feedback, queries, or suggestions on the RIO. Please get in touch with us by emailing any or all of the corresponding authors: Jonah Walker: jonah.mwalker@gmail.com, Sean Stankowski: seanstankowski@gmail.com, Roger Butlin: r.k.butlin@sheffield.ac.uk.