Origin of the Rare Hybrid Genus × Trisetokoeleria Tzvelev ( Poaceae ) According to Molecular Phylogenetic Data.

In our article, we analyzed new data on the origin of the hybrid genus × Trisetokoeleria . According to the morphological criteria × T. jurtzevii is a hybrid between Koeleria asiatica s. l. and Trisetum spicatum , × T. taimyrica , and originated from Koeleria asiatica s. l. and Trisetum subalpestre , × T. gorodkowii , a hybrid between Koeleria asiatica and Trisetum ruprechtianum . Later × T. taimyrica was transferred to Koeleria . Parental taxa are prone to active hybridization themselves, thus, new methods of next-generation sequencing (NGS) were needed to clarify the relationships of these genera. For NGS we used the fragment 18S rDNA (part)-ITS1-5.8S rDNA (totally 441 accessions). We analyzed ITS1-5.8S rDNA-ITS2 region, trn L- trn F and trn K- rps 16 from eight samples of the five species, using the Sanger method: × Trisetokoeleria jurtzevii , × T. taimyrica , Koeleria asiatica , Sibirotrisetum sibiricum (= Trisetum sibiricum ), and Trisetum spicatum . We also studied the pollen fertility of × Trisetokoeleria and its possible progenitors. Our data partly contradicted previous assumptions, based on morphological grounds, and showed us a picture of developed introgression within and between Koeleria and Trisetum . × T. jurtzevii , a totally sterile hybrid formed rather recently. We can suppose that × T. jurtzevii is a hybrid between K. asiatica and some Trisetum s. str. Species, but not T. spicatum . × T. gorodkowii , a hybrid in the stage of primary stabilization; it has one unique ribotype related to T. spicatum s. l. The second parental species is unrelated to Trisetum ruprechtianum . × T. taimyrica and is a stabilized hybrid species; it shares major ribotypes with the T. spicatum / T. wrangelense group and has a minor fraction of rDNA related to genus Deyeuxia s. l.