A standardised framework for classifying estimates of reproductive isolation.

Understanding reproductive isolation (RI) between lineages is a central goal of speciation research. While the strength of RI has been estimated across a broad range of taxa, synthesizing these data remains challenging, partially because we lack a common language for classifying and reporting RI estimates. Here, we present the Reproductive Isolation Ontology (RIO), a structured framework designed to standardize the classification of RI estimates across most sexually reproducing organisms. The RIO comprises 3 interrelated domains, each organized into a nested hierarchy of classification terms. We demonstrate the utility of this approach and call for researchers to adopt and expand the RIO to facilitate the integration of speciation research.