Myriophyllum rubricaule Valk. & Duist. revisited

Myriophyllum rubricaule has been described as “only known from cultivation” and the authors assumed the species to be native to South America. While visiting Chile for a conference, two of the authors seized the opportunity to check on the natural occurrences of M. aquaticum or possibly M. rubricaule. Several populations of M. rubricaule were observed in the Araucania region and the species was found to be monoecious. Subsequent analysis of herbarium collections and iNaturalist records resulted in a provisional native range for the species to be Chile, from the region of Valparaíso to the Los Rios region in the south, and a further expansion of the introduced range in Europe to include the United Kingdom, Denmark and Austria. Molecular results further strengthen the notion that M. rubricaule is indeed a separate species.