Phylogeny and biogeography of Calamagrostis (Poaceae: Pooideae: Poeae: Agrostidinae), description of a new genus, Condilorachia (Calothecinae), and expansion of Greeneochloa and Pentapogon (Echinopogoninae)

Abstract

To investigate the evolutionary relationships and biogeographical history among the species of Calamagrostis and other members of subtribes Agrostidinae, Calothecinae, Echinopogoninae, and Paramochloinae, we generated a phylogeny based on DNA sequences from one nuclear ribosomal (ITS) and three plastid regions (rpl32-trnL spacer, rps16-trnK spacer, and rps16 intron). Based on our phylogeny, we identified seven species groups (clades) within Calamagrostis: the Meridionalis group comprises two species from Central and South America, the Americana group comprises species from North America, the Deyeuxia and Epigeios groups comprise species from Eurasia, the Orientalis group comprises species from East Asia, the Purpurea group comprises species from Eurasia and North America, and the Calamagrostis group comprises species from Eurasia and North America. We hypothesize that Calamagrostis originated in North America with the primary split of the Meridionalis group, followed by split between the autochthonous Americana group and two future Eurasian branches encompassing all the remaining groups, which possibly dispersed into Eurasia independently. The molecular data suggest that hybridization and genomic introgression played a prominent role in the evolutionary history of Calamagrostis. We propose a new genus, Condilorachia, segregated from Trisetum s.l., with three species from South America for which we propose new combinations: Condilorachia bulbosa, Condilorachia brasiliensis, and Condilorachia juergensii; a new combination in Greeneochloa, Greeneochloa expansa; and the subsumption of Dichelachne into Pentapogon with 20 new combinations: Pentapogon avenoides, Pentapogon brassii, Pentapogon chaseianus, Pentapogon crinita, Pentapogon densus, Pentapogon frigidus, Pentapogon gunnianus, Pentapogon hirtella, Pentapogon inaequiglumis, Pentapogon lautumia, Pentapogon micrantha, Pentapogon parva, Pentapogon quadrisetus, Pentapogon rara, Pentapogon robusta, Pentapogon scaberulus, Pentapogon sclerophyllus, Pentapogon suizanensis, Pentapogon sieberiana, and Pentapogon validus. We provide a diagnosis, description, and a key to the species of Condilorachia.

Grasses through space and time: An overview of the biogeographical and macroevolutionary history of Poaceae

“…Koeleriinae clade 1 includes the genera Acrospelion Besser s.l. (10 spp., Eurasia; Barberá et al, 2017Barberá et al, , 2020 Echinopogoninae Soreng (Soreng et al, 2017) has stem and crown dates of 15.56 and 9 Ma and has a peculiar split in distribution, Relchela in Patagonian South America, Greeneochloa in North America and Hawaii (Peterson et al, 2019b(Peterson et al, , 2022c, and the rest in Australasia, with a few species more widespread in the Pacific Ocean basin. It includes Echinopogon P. Beauv.…”

“…), Pentapogon R. Br. (at least 22 spp., Australasia, Peterson et al, 2022c), Relchela Steud. (1 sp., South America, Patagonia, sister to the rest of Echinopogoninae).…”

“…(1 sp., South America, Patagonia, sister to the rest of Echinopogoninae). Generic boundaries are unsettled as the group contains Australasian species often placed in Deyeuxia, but species sampling is limited (Peterson et al, 2022c). Based on a phylogeny using four DNA markers, Peterson et al (2022c) subsume all 11 species of Dichelachne Endl.…”

“…Generic boundaries are unsettled as the group contains Australasian species often placed in Deyeuxia, but species sampling is limited (Peterson et al, 2022c). Based on a phylogeny using four DNA markers, Peterson et al (2022c) subsume all 11 species of Dichelachne Endl. (Edgar & Connor, 1982;Simon et al, 2009) into Pentapogon (Kodela et al, 2009).…”

“…Calothecinae Soreng (Soreng et al, 2015b) has a stem date of 12.58 Ma and contains 10 genera (Da Silva et al, 2022;Peterson et al, 2022c), with all species occurring in South America and one reaching Central America. The monograph by Matthei (1975) (Soreng et al, 2015b;Persson & Rydin, 2016).…”