A comprehensive sampling of species sheds light on the molecular phylogenetics of Calothecinae (Poaceae, Pooideae): evidence for a new subtribe and multiple genera within the Chascolytrum clade

The circumscription of subtribe Calothecinae has undergone several changes
since its description. Currently, three genera are considered in the
subtribe: Chascolytrum, Laegaardia and Paramochloa, although no
phylogenetic evidence for the placement of the two last genera was
published so far. In this study we aim to evaluate the circumscription of
Calothecinae and the infrageneric classification recently proposed for
Chascolytrum using a more comprehensive sampling of taxa and molecular
markers. We included species of all genera of Calothecinae, plus two South
American species of Trisetum s.l. that have been suggested to be related
to Chascolytrum, and representatives from subtribes Agrostidinae,
Echinopogoninae, Brizinae, Torreyochloinae, Phalaridinae and Koeleriinae.
We performed Bayesian and Maximum Likelihood analyses using a total of six
molecular markers, including four plastid DNA regions (atpF-atpH, matK,
rps16 intron, and trnL-trnF) and two ribosomal nuclear regions (ITS and
ETS). Our results revealed that neither Calothecinae nor Chascolytrum are
monophyletic considering their last circumscription. Trisetum brasiliense
and T. bulbosum appeared nested to Chascolytrum, and are formally included
in Calothecinae as incertae sedis. More studies are needed to confirm
their taxonomic position. Based on morphological characters, Laegaardia
and Paramochloa are transferred to the new subtribe Paramochloinae, and
Chascolytrum is splitted in nine different genera, of which two are newly
described: Boldrinia (gen. nov.), Calotheca, Chascolytrum, Erianthecium,
Lombardochloa, Microbriza, Poidium, Rhombolytrum, and Rosengurttia (gen.
nov.).