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

“…belong to this subtribe but needed further study to place them more precisely. Peterson et al (2022c) placed these two species, and T. juergensii Hack., in Condilorachia P.M. Peterson, Soreng & Romasch. Da Silva et al (2022) revised the other genera: Boldrinia L.N.Silva (1 sp., Uruguay), Calotheca Desv.…”

“…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).…”

“…DaSilva et al (2022) found that Trisetum brasiliense Louis-Marie and T. bulbosum Hitch. belong to this subtribe but needed further study to place them more precisely Peterson et al (2022c). placed these two species, and T. juergensii Hack., in Condilorachia P.M.Peterson, Soreng & Romasch.…”

The biogeography of grasses (Poaceae)

“…Four of the manuscripts in this issue include new dated biogeographical analyses (Gallaher et al, 2022;Peterson et al, 2022b;Soreng et al, 2022a;Zhou et al, 2022); three comprise new phylogenetic analyses with subsequent taxonomic novelties (Da Silva et al, 2022;Peterson et al, 2022aPeterson et al, , 2022c, one is an ecological study investigating functional traits in a clade of savanna/wetland grasses (Arthan et al, 2022), one looked at the current distribution of the grasses over the Australian continent to determine migration directionality (Bryceson & Morgan, 2022), and one is an updated classification of the family primarily based on molecular phylogenetic studies (Soreng et al, 2022).…”

New combinations in Pentapogon for Aotearoa / New Zealand taxa earlier placed in Deyeuxia (Poaceae)

“…(Tzvelev, 1976;Clayton, Renvoize, 1986;Soreng, Greene, 2003), or separating the two genera (Watson, Dallwitz, 1992;Edgar, 1995;Kellogg, 2015). Molecular DNA data have helped to resolve this taxonomic tangle such that Soreng et al (2015Soreng et al ( , 2017, Saarela et al (2017), Peterson et al (2022), treated Deyeuxia s. str. in synonymy within Calamagrostis (subtribe Agrostidinae).…”