Reinstatement of the Southern Andean Genus Stenodraba (Brassicaceae) Based on Molecular Data and Insights from its Environmental and Geographic Distribution

Abstract—

Stenodraba (Brassicaceae) included a group of eight species distributed along the Andes of South-Central Argentina and Chile. All of its species are currently treated in Pennellia (Tribe Halimolobeae) and Weberbauera (Tribe Thelypodieae). However, the phylogeny of Stenodraba and its tribal placement were never analyzed using molecular data. The lack of such studies, as well as the paucity of herbarium collections suggesting that some species are vulnerable and/or endangered, prompted us to address the molecular phylogeny of Stenodraba. For this purpose, we generated comprehensive molecular phylogenies using nuclear (ITS) and plastid (trnL-F and trnH-psbA) data and conducted different niche comparisons in the environmental and geographic spaces using climate data processed both by ordination and species distribution modelling (SDM) techniques. Results from phylogenetic analyses demonstrated that Stenodraba belongs to the South American tribe Eudemeae and is related to the genera Aschersoniodoxa, Brayopsis, Dactylocardamum, and Eudema. Stenodraba species formed two strongly supported clades, and although molecular data did not recover monophyly of the genus, this hypothesis could not be rejected with our data. The main clades were differentiated in their climatic niches (both in the environmental and geographical spaces), and niche overlap was greater within than between clades. Systematic implications, including a key distinguishing Stenodraba from the remaining genera of Eudemeae and a synopsis of its species, are also provided. The new combination S. lagunae is proposed.