A new species of Porophyllum (Asteraceae: Tageteae) from the northwest of Argentina, and the first record of female plants of Porophyllum cabrerae

Porophyllum riparium, a new species of the genus Porophyllum, is described. Morphological details, illustration, geographical distribution, and photographs in its natural habitat are provided. This new species occurs in the northwest region of Argentina, in Salta, Jujuy and Tucumán Provinces, in the Yungas biogeographical province. It is usually found on rocky and sandy soils, as well as along riverbanks. Porophyllum riparium is characterized by being an annual or short-lived perennial, glaucous, odoriferous, monoecious herb, 15–80(–130) cm tall, with sessile or attenuate into a pseudopetiole, linear-elliptic leaves with submarginal and subapical semi-pellucid oil cavities, lemon-colored infundibuliform corollas and exserted brownish anthers. Additionally, female plants of Porophyllum cabrerae were documented for the first time, photographs and descriptions of their female florets are included. Also, a key to identify northwestern species of Porophyllum is provided.