Phylogenomics and Systematics of Overlooked Mesoamerican and South American Polyploid Broad-Leaved Festuca Grasses Differentiate F. sects. Glabricarpae and Ruprechtia and F. subgen. Asperifolia, Erosiflorae, Mallopetalon and Coironhuecu (subgen. nov.)

Allopolyploidy is considered a driver of diversity in subtribe Loliinae. We investigate the evolution and systematics of the poorly studied Mesoamerican and South American polyploid broad-leaved Festuca L. species of uncertain origin and unclear taxonomy. A taxonomic study of seven diagnostic morphological traits was conducted on a representation of 22 species. Phylogenomic analyses were performed on a representation of these supraspecific taxa and all other Loliinae lineages using separate data from the entire plastome, nuclear rDNA 45S and 5S genes, and repetitive DNA elements. F. subgen. Mallopetalon falls within the fine-leaved (FL) Loliinae clade, whereas the remaining taxa are nested within the broad-leaved (BL) Loliinae clade forming two separate Mexico–Central–South American (MCSAI, MCSAII) lineages. MCSAI includes representatives of F. sect. Glabricarpae and F. subgen. Asperifolia plus F. superba, and MCSAII of F. subgen. Erosiflorae and F. sect. Ruprechtia plus F. argentina. MCSAII likely had a BL Leucopoa paternal ancestor, MCSAI and MCSAII a BL Meso-South American maternal ancestor, and Mallopetalon FL, American I–II ancestors. Plastome vs. nuclear topological discordances corroborated the hybrid allopolyploid origins of these taxa, some of which probably originated from Northern Hemisphere ancestors. The observed data indicate rapid reticulate radiations in the Central–South American subcontinent. Our systematic study supports the reclassification of some studied taxa in different supraspecific Festuca ranks

Phylogenetics of the paleartic model grass "brachypodium sylvaticum" uncovers two divergent oriental and occidental micro-taxa lineages

Brachypodium sylvaticum has been selected as a model for perennial grasses, and considerable genomic resources have been generated and a reference genome and several resequenced pangenome accessions are available for this species. Despite these genomic advances, the evolution and systematics of diploid B. sylvaticum s. l. is almost unknown. The B. sylvaticum complex is formed by up to seven taxonomically close micro-taxa which differentiate from typical B. sylvaticum s. s. based on a few morphological features. Moreover, some of them show some largely disjunct geographic distributions on both sides of their native Palearctic region. In this study, we used a phylogenomic approach including representative populations from the oriental and occidental distribution range of B. sylvaticum micro-taxa to elucidate their evolutionary relationships and assess the systematic value of the morphological features that separate them. A combined plastome and nuclear phylogenetic tree supports an early split and high divergence of the oriental lineage, showing the close relationship of the Himalayan B. sylvaticum var. breviglume lineages to the Pacific B. miserum / B. kurilense clade, and the contrasting large homogeneity and low divergence of the occidental European, N African and SW and C Asian lineage, with several B. sylvaticum s. s., B. spryginii, and B. glaucovirens samples showing identical or similar sequences. Divergence time estimate analysis suggests that the oriental lineage diverged from the common ancestor in the early Pleistocene (2.0 Ma), followed by subsequent colonization and isolations in the Himalayas (2.0 – 1.7 Ma) and the Far East (0.36 Ma) in more recent times, while the occidental lineage split in the Mid-Late Pleistocene (0.97 Ma), followed by rapid radiation and postglacial spread in the western Paleartic during the last thousand years