Defining species objectively and consistently remains a challenge for plants distributed in remote regions where there is often a lack of sufficient previous specimens. Su et al. use the genus Orinus (Poaceae) as a model system and apply multiple approaches and lines of evidence to determine species boundaries for plants occurring in the Qinghai–Tibet Plateau. They find compelling evidence that the six previously recognized species of the genus that were examined should be reduced to two, with new circumscriptions, and a third, identified in this study, should be described as a new species. This empirical study highlights the value of applying genetic differentiation, morphometric statistics and ecological-niche modelling in an integrative approach to re-circumscribing species boundaries.