Rediscovery and confirmation of the presence of Pycnophyllum macropetalum (Caryophyllaceae) for the Argentinian flora

Pycnophyllum macropetalum Matff. is a species originally described for the Andes of Chile which has also been collected in Bolivia and in Argentina. Presence of P. macropetalum in Argentina is based on a single sterile specimen collected in 1945. For this reason, and because P. macropetalum is morphologically very similar to P. molle, the species was excluded from the Argentinian Flora; however, recently, a population of P. macropetalum has been found in the province of Jujuy (Argentina). Therefore, the objective of this work is to describe and to illustrate this species, to provide environmental notes about the habitat where it was found, and to provide a map of the geographic distribution of the species for Argentina, Bolivia and Chile. Furthermore, based on molecular analyzes of the collected specimen, the morphological identification is corroborated, and the monophyly of the genus is confirmed. Finally, a dichotomous key is provided to differentiate the four Pycnophyllum species recorded in Argentina.