Phylogenetic lineages and the role of hybridization as driving force of evolution in grass supertribe Poodae

Abstract

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,

Museomics Unveil the Phylogeny and Biogeography of the Neglected Juan Fernandez Archipelago Megalachne and Podophorus Endemic Grasses and Their Connection With Relict Pampean-Ventanian Fescues

“…Complete and partial plastomes as well as the nuclear rDNA cistron and ITS data supported the phylogenetic placement of the studied Fernandezian Podophorous bromoides, Megalachne berteroniana, and M. masafuerana species within the American-Vulpia-Pampas fine-leaved Loliinae clade (Figures 2, 3 and Supplementary Figures S1A-C). Our results corroborate the early suggestions of Tateoka (1962) who indicated a close affinity of Megalachne to Festuca based on shared morphological and serological traits, and the recent phylogenetic findings of Schneider et al (2011Schneider et al ( , 2012 and Tkach et al (2020) who placed them within the fine-leaved Loliinae, and definitively discard its classification within either Bromeae or Duthieinae. Our results have also contributed to enlarge the paraphyly of Festuca, which now accounts to up to 14 Loliinae genera nested within its main fine-leaved (Ctenopsis, Dielsiochloa, Hellerochloa, Megalachne, Micropyrum, Narduroides, Podophorus, Psilurus, Vulpia, Wangeheimia), intermediate (Castellia), and broad-leaved (Lolium, Micropyropsis, Pseudobromus) lineages (Supplementary Figure S2C; Inda et al, 2008;Minaya et al, 2017).…”

“…Nonetheless, the comprehensive morphological and molecular study of the newly delimited tribe Duthieeae of Schneider et al (2011) demonstrated, using ITS sequences, that Megalachne and Podophorus were not part of this early diverging pooid lineage, and suggested that they likely belonged to the Aveneae/Poeae complex. In recent studies, phylogenetic analyses conducted by Schneider et al (2012) and Tkach et al (2020) using, respectively, nuclear ITS and plastid matK sequences and nuclear ITS and ETS and plastid matK, trnK, and trnLF sequences corroborated it, showing that Megalachne was nested within the fine-leaved Loliinae clade.…”

“…In addition, two new Loliinae samples from South America and one sample from South Africa not studied before (Table 1) were sequenced for the nuclear ITS (ITS1-5.8S-ITS2) and the plastid trnTL (trnT-trnL intergenic spacer) and trnLF (trnA-Leu, trnL-trnF intergenic spacer, trnA-Phe) loci, together with 97 samples from a wide-sampling of all currently known Loliinae lineages (Inda et al, 2008;Minaya et al, 2017). Although species of Megalachne and Podophorus and other fine-leaved Loliinae genera have been synonymized to Festuca, and those of broad-leaved Loliinae to different festucoid genera in recent studies (Soreng et al, 2017;Tkach et al, 2020), we follow the Festuca sensu lato classification of Catalan et al (2007) which is based on an evolutionary systematic criterion that is nomenclaturally conservative and maintains a paraphyletic Festuca (with subgenera and sections) and other traditionally recognized genera until more complete phylogenetic studies of Loliinae are conducted. We have selected this scenario because of present uncertainties about the phylogeny of several Loliinae lineages and taxonomic and nomenclatural instability of the Festuca sensu stricto (i.e., fineleaved Loliinae lineages) classification, that would leave some broad-leaved Loliinae lineages without name or with unclear adscription (e.g., some broad-leaved "Festuca").…”

“…It could be possible, however, that genera phylogenetically embedded within the large Loliinae clade or its fine-leaved subclade would be subordinated to Festuca, once all or most of the Loliinae taxa are phylogenetically analyzed and consistent synapomorphies are defined. At this respect, nomenclatural combinations have been proposed for the fine-leaved Megalachne ( (Tkach et al, 2020). Sixteen additional species were added as outgroups to provide reliable fossil calibration points for molecular dating ( Supplementary Table S1).…”

Agrostis meyenii Trin. (Poaceae, Agrostidinae): first records from Peru, including taxonomic notes and an identification key

“…During herbarium research at the United States National Herbarium (US), specimens of Agrostis meyenii Trin., a species recorded further south in Bolivia, Argentina, and Chile (Renvoize 1998;Rúgolo de Agrasar 2012;Jørgensen et al 2014), were encountered and mark the northernmost distribution of this species recorded to date. With the addition of A. meyenii, and including taxa previously circumscribed in Bromidium based on indications from recent phylogenetic research (Tkach et al 2020), it is currently estimated that 13 species of Agrostis are present in Peru (A. breviculmis Hitchc. ; A. foliata Hook.f.…”