A new classification of Gentianaceae tribe Gentianeae subtribe Swertiinae

Abstract In its current circumscription, subtribe Swertiinae of Gentianaceae contains the genera Bartonia , Comastoma , Frasera , Gentianella , Gentianopsis , Halenia , Jaeschkea , Latouchea , Lomatogonium , Megacodon , Obolaria , Pterygocalyx , Swertia and Veratrilla . Generic limits have been unclear in many instances in the past, and indeed early molecular systematic studies, based on a very limited number of DNA sequences, could demonstrate that Gentianella , Gentianopsis , Jaeschkea , Lomatogonium and Swertia are non‐monophyletic, with a high degree of polyphyly particularly in Swertia . Recently, a molecular phylogenetic analysis of the subtribe using a large number of nuclear (>1000 orthologous loci) and plastid (27 to 64 regions) sequences resulted in a well‐resolved and well‐supported phylogenetic tree confirming these earlier findings. This phylogenetic tree has not yet been translated into a classification formally recognizing only monophyletic groups. We used this latest phylogenetic tree of Swertiinae, supplemented by species sampled in other molecular phylogenetic studies, to investigate whether the lineages identified are morphologically, karyologically or geographically distinguishable from each other and can be recognized at generic rank. We conclude that whereas Latouchea , Megacodon and Obolaria can be maintained as separate genera, Gentianopsis is monophyletic only by inclusion of Pterygocalyx . With respect to the remaining genera, we show that many of the various lineages particularly of Gentianella and Swertia are difficult or impossible to distinguish from each other. We conclude that this situation is taxonomically best accounted for by inclusion of Bartonia , Comastoma , Frasera , Gentianella , Halenia , Jaeschkea , Lomatogonium and Veratrilla in Swertia . Our classification in our opinion then contains only stable and diagnosable clades.