Two new diploid species, Aira minoricensis and Aira hercynica are described and illustrated, along with chromosome counts, risk assessment, distribution and habitat, phenology, and comparisons with morphologically similar species. A comparative table and a key for the species of Aira for the Iberian Peninsula and the Balearic Islands are provided to assist in the identification of these overlooked species, and their relationships to other taxa are discussed.

Supplementary Appendix
I. Specimens examined for morphometric analyses
II. Other specimens examined for comparative morphology
III. Voucher of chromosome numbers