Wandering throughout South America: Taxonomic revision of Tradescantia subg. Austrotradescantia (D.R.Hunt) M.Pell. (Commelinaceae).

I present the first taxonomic revision for T. subg. Austrotradescantia, based on extensive field, cultivation and herbaria studies. I accept 13 species, three of them (i.e. T. atlantica, T. hertweckii and T. tucumanensis) being described as new in the present study. I provide an identification key to the species, distribution maps, descriptions, comments, conservation assessments and illustrations for all species. The troublesome weed T. fluminensis has its specific limits clarified and its native range is presented so it can serve as a basis to better understanding its ecological requirements and to help control it throughout its invasive range. Furthermore, I highlight that T. mundula, a commonly neglected species closely related to T. fluminensis, might also represent a troublesome weed. Tradescantia mundula has been widely introduced in cultivation under the name T. albiflora and seems to have also escaped from cultivation. However, due to the hitherto poorly understood specific limits of T. fluminensis, T. mundula has been treated as a mere cultivar of T. fluminensiss.s.