To investigate the evolutionary diversification and morphological evolution of grass supertribe Poodae (subfam. Pooideae, Poaceae) we conducted a comprehensive molecular phylogenetic analysis including representatives from most of its accepted genera. We focused on generating a DNA sequence dataset of plastid matK gene-3′trnK exon and trnL-trnF regions and nuclear ribosomal (nr) ITS1-5.8S gene-ITS2 and ETS that was taxonomically overlapping as completely as possible (altogether 257 species). The idea was to infer whether phylogenetic trees or certain clades based on plastid and nrDNA data correspond with each other or discord, revealing signatures of past hybridization. The datasets were analysed separately, in combination, by excluding taxa with discordant placements in the individual gene trees and with duplication of these taxa in a way that each duplicate has only one data partition (plastid or nrDNA). We used maximum likelihood, maximum parsimony and Bayesian approaches. Instances of severe conflicts between the phylogenetic trees derived from both datasets, some of which have been noted earlier, point to hybrid origin of several lineages such as the ABCV clade encompassing several subtribes and subordinate clades,

The phylogenetic relationships of 31 genera of the traditional grass tribe Aveneae, with focus on Southeast Asian species of Helictotrichon, were examined using DNA sequences of the plastid matK-psbA region, nuclear ITS, the nuclear single-copy gene topoisomerase 6 (Topo6) spanning two introns and morphology. A molecular phylogenetic analysis was performed for 121 species applying maximum parsimony and Bayesian methods. Additionally we surveyed 11 Southeast Asian taxa for structural spikelet characters including lemmas, lodicules and ovaries. The phylogenetic results of the three molecular markers revealed that several Southeast Asian species traditionally accommodated in Helictotrichon are misplaced in this genus except for H. abietetorum, H. hideoi and H. leianthum. The placement of H. polyneurum and H. sumatrense in the genus Helictotrichon requires further investigation as suggested by morphological and preliminary molecular data. Due to the occurrence of different sequence types of ITS and Topo6, both nuclear DNA markers suggested an allopolyploid origin for several Southeast Asian taxa. (1) In Helictotrichon parviflorum and H. potaninii two different sequence types of Topo6 occur, closely similar to those of Trisetum and Helictotrichon, respectively. Nuclear ITS data of both species point to affinities with Trisetum and related genera but not to Helictotrichon. Both species belong to a hitherto unknown genus that is morphologically distinct from Trisetum and Helictotrichon and is named Tzveleviochloa. (2) Two copy types (A and B) of Topo6 previously identified in African Trisetopsis, a genus encompassing predominantly sub-Saharan species that traditionally had been ascribed to Helictotrichon, also occur in two Southeast Asian species, i.e., H. junghuhnii and H. virescens. In agreement with morphological data both species need to be transferred to Trisetopsis. This expands the hitherto known eastern edge of the range of Trisetopsis from the Arabian Peninsula to China. (3) Additionally, the Chinese H. altius has a copy type sequence of Topo6 similar to that of Trisetopsis but not of Helictotrichon in its genome, whereas its plastid DNA fits Helictotrichon and relatives. Along with morphological characters this supports intermediacy between Trisetopsis and Helictotrichon. Therefore H. altius is probably an intergeneric hybrid, here named ×Trisetopsotrichon altius. The taxonomically difficult genus Helictotrichon s.l. in tropical to temperate southeastern Asia becomes disassembled into Helictotrichon s.str., the new genus Tzveleviochloa, gen. nov., and the nothogenus ×Trisetopsotrichon, nothogen. nov. The following combinations are introduced: Trisetopsis aspera, comb. nov., T. junghuhnii, comb. nov., T. virescens, comb. nov., ×Trisetopsotrichon altius, comb. nov., Tzveleviochloa burmanica, comb. nov., T. parviflora, comb. nov., T. potaninii, comb. nov. Supplementary Material DNA sequence alignments are available in the Supplementary Data section of the online version of this article at

We examined the morphology and molecular phylogeny of several genera of the traditional grass tribe Aveneae, with focus on Helictotrichon and the recently described genus Trisetopsis from tropical and subtropical Africa. Altogether we surveyed 34 taxa for structural characters of the spikelets including lemmas, lodicules and ovaries. Sequences of the nuclear single–copy gene topoisomerase 6 (Topo6) spanning two introns, nuclear ribosomal ITS and the plastid matK–psbA region were generated for 81 taxa and analyzed by maximum parsimony and Bayesian methods. The phylogenetic results show African Trisetopsis in all molecular markers investigated clearly distinct from Helictotrichon, which in its new circumscription encompasses only Northern Hemisphere species. Morphological data support exclusion of the African species from Helictotrichon as a separate genus. The Topo6 sequences reveal a strong geographical pattern of variation which allows for comprehensive phylogeographic analyses. Two copy types of Topo6 are present in Trisetopsis (A and B). They are strongly different from that found in the Eurasian species of Helictotrichon. Copy type A probably descended from South African T. longa or T. rogerellisii, which appear to be the only African species with only type A. All other species of Trisetopsis contain both types A and B. Unexpectedly, type B is widespread in the New World (Calamagrostis, Graphephorum, Peyritschia, Sphenopholis) but, apart from the Trisetopsis allopolyploids, is absent from Africa. Trisetopsis imberbis is introduced as a new combination.

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18To investigate the evolutionary diversification and morphological evolution of grass 19 supertribe Poodae (subfam. Pooideae, Poaceae) we conducted a comprehensive molecular 20 phylogenetic analysis including representatives from most of their accepted genera. We 21 focused on generating a DNA sequence dataset of plastid matK gene-3'trnK exon and trnL-22 trnF regions and nuclear ribosomal ITS1-5.8S gene-ITS2 and ETS that was taxonomically 23 overlapping as completely as possible (altogether 257 species). The idea was to infer whether 24 phylogenetic trees or certain clades based on plastid and nuclear DNA data correspond with 25 each other or discord, revealing signatures of past hybridization. The datasets were analysed 26 using maximum parsimony, maximum likelihood and Bayesian approaches. Instances of 27 severe conflicts between the phylogenetic trees derived from both datasets, some of which 28 have been noted earlier, unambiguously point to hybrid origin of several lineages (subtribes, 29 groups of genera, sometimes genera) such as Phalaridinae,