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Nogueira da Silva, Leonardo [1], Saarela, Jeffery [2], Essi, Liliana [3], Chies, Tatiana [1].

Phylogenetic novelties of Calothecinae (Poaceae, Pooideae, Poeae): evidence for a new subtribe and multiple genera within the Chascolytrum clade.

The circumscription of the grass subtribe Calothecinae has undergone several changes since its description in 2015. Currently, it comprises Chascolytrum and the recently described genera Laegaardia and Paramochloa, both segregated from Calamagrostis. Recently, a molecular and morphological study focused on Chascolytrum recognized eight section within it. In this study we evaluate the circumscription of Calothecinae and the recently proposed infrageneric classification of Chascolytrum based on a phylogeny with more comprehensive taxon and molecular marker sampling than in previous studies. We sampled all Calothecinae genera, all but one Chascolytrum species, two South American Trisetum s.l. species related to Chascolytrum, and representatives of closely related subtribes Agrostidinae, Brizinae, and Echinopogoninae besides the more distantly related subtribes Koeleriinae, Phalaridinae, and Torreyochloinae within Poaceae tribe Poeae. We performed Bayesian and Maximum Likelihood analyses based on four plastid DNA regions (atpF-atpH, matK, rps16 intron, and trnL-trnF) and two nuclear ribosomal regions (ITS and ETS). Since no statistically supported topological conflicts were detected between the two datasets, we combined datasets for final analyses. Our results revealed that neither Calothecinae nor Chascolytrum are monophyletic as currently recognized once Trisetum brasiliense and T. bulbosum are nested within Chascolytrum. The two Trisetum species are included in Calothecinae as incertae sedis. Laegaardia and Paramochloa form a clade (Clade A) that is sister to the Chascolytrum + Trisetum clade, and based on morphological characters Laegaardia and Paramochloa are transferred to the new subtribe Paramochloinae. Our Chascolytrum phylogeny is better resolved and supported than in previous studies, and two major clades are identified: (1) Clade B, encompassing species previously accepted in Chascolytrum sects. Lombardochloa, Hildaea, and Poidium, with T. brasiliense nested within this clade and placed as sister to C. sects. Hildaea + Poidium clade; (2) Clade C, encompassing species previously accepted in Chascolytrum sects. Calotheca, Microbriza, Tricholemma, Obovatae, and Chascolytrum. Trisetum bulbosum was recovered in a polytomy with Clades B and C. Based on these results we divide Chascolytrum into nine genera, including two new ones: Boldrinia (gen. nov., one species), Calotheca (one species), Chascolytrum (six species), Erianthecium (one species), Lombardochloa (one species, two varieties), Microbriza (one species), Poidium (nine species, two varieties), Rhombolytrum (three species), and Rosengurttia (gen. nov., one species). We also propose six new combinations: Boldrinia parodiana, Poidium juergensii var. angustilemma, Poidium latifolium, Poidium serranum, Rhombolytrum koelerioides, and Rosengurttia monandra.

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1 - Universidade Federal Do Rio Grande Do Sul, Botany, Av. Bento Goncalves, 9500 Prédio 43433, Porto Alegre RS, RS, 90470-260, Brazil
2 - Canadian Museum of Nature, Beaty Centre for Species Discovery & Botany Section, 1740 Pink Road, Gatineau, Quebec, J9J 3N7, Canada
3 - Universidade Federal de Santa Maria, 3Departamento de Biologia, Av. Roraima, 1000, Santa Maria, RS, 97105-900, Brazil

cool-season grasses
generic circumscription
Molecular Systematics
new subtribe
subtropical grasslands

Presentation Type: Oral Paper
Session: SYSTVI, Systematics VI: Monocots to Eurosids I
Location: Virtual/Virtual
Date: Friday, July 23rd, 2021
Time: 10:00 AM(EDT)
Number: SYSTVI001
Abstract ID:409
Candidate for Awards:None

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