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In this study, sequence data from the inert nuclear region ITS1‐5.8S rDNA‐ITS2 and the chloroplast region trnL–F, as well as a few morphological characters, are analysed to the relationships among known annual Poa (bluegrasses). It is shown that all taxa from the Poa annua aggregate distinguished by lemma characters and growth form have identical ITS and trnL–trnF sequences, all ITS sequences of this aggregate are the same as thethose of P. supina, and all trnL–trnF sequences are homologous with those of P. infirma. Furthermore, no differences were found between unusual morphotypes of P. supina with short spinules on their panicle branches and typical plants, but Siberian samples were found to have a slightly differentiated trnL–trnF region. These results suggest a hybrid origin of the Asian annual bluegrasses. Their maternal genome is close to that of P. sect. Homalopoa, but their ITS sequences are different. Some ITS sequences from annual Asian bluegrasses are resolved among representatives of P. sect. Stenopoa while for other (morphologically closely similar) species they fall in a clade with representatives of P. sect. Malacanthae. The latter group is distant from P. sect. Ochlopoa and is better treated as a separate section, viz P. sect. Acroleucae. The American annual bluegrasses are heterogeneous and also rather distant from P. sect. Ochlopoa. Poa chapmaniana, a species with cleistogamic flowers, is nested among the basal Subantarctic sections, far away from the taxa with which it has previously been considered related. It is indeed closer to P. sect. Ochlopoa than to other annual American bluegrasses. Thus, the studied annual species in fact belong to four independent evolutionary lines (or six including the separate genus Eremopoa and the Turkish Poa jubata), one of which, Acroleucae, has gone through three reticulation events. As in previous studies, our analysis did not support the generic status of P. sect. Ochlopoa.

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Phylogenetic position of the unique grass genus Coleanthus within the tribe Poeae s. str. is discussed based on molecular phylogenetic analysis of the marker sequences, ITS and trnL–trnF. Moreover, taxa more or less related to Coleanthus were involved in our study for the maximal accuracy of the molecular phylogenetic analysis. Subtribe Coleanthinae (=Puccinelliinae) is monophyletic according to both datasets, nuclear and chloroplast genes, that probably shows certain evolutionary distance from other Poeae s. str. We confirmed the results of previous morphological studies that placed Coleanthus close to the genus Phippsia but at the same time we have not found any evidences of the affinity between the genus Phippsia and the second putative ancestor, Deschampsia. The clade which contains Coleanthus and Phippsia occupies the sister position to all other genera of the subtribe Coleanthinae. The genus Phippsia produces hybrids with Puccinellia, ×Pucciphippsia, but the relationship obtained by our data is far more distant that was considered before from its morphological features. The genus Puccinellia forms a single monophyletic clade—sister to the genus Sclerochloa and former Colpodium s. l. (Paracolpodium, Catabrosella) which are monophyletic with Catabrosa. In partial contradiction to previous research (Soreng et al. 2015)—we found that the subtribe Coleanthinae is rather distant from two-chromosome grasses in ITS analysis though chloroplast genes show the sister position of the species from the 2-chromosome grasses group, Colpodium versicolor (2n = 4), to Coleanthinae. Also we detected multiple reticulation events in the tribe Poeae s. str. and some of them—within the subtribe Coleanthinae. This can explain an uncertain position of the two-chromosome grasses in relation to Coleanthinae.