Gomphrena meyeniana is an extremely variable species from the Andean highlands, which has attracted the attention of many botanists because it is the world’s highest-elevation C4 eudicot and because of its wide morphological variability. It has the typical high-Andean plant morphology, with small leaves tightly clustered on a thick rootstock. The large range of morphological variation within this species, coupled with the varying opinions on the existence of several species or infra-specific taxa, and the lack of molecular information has made the clarification of the G. meyeniana complex a challenge. Our approach was to perform a broad spectrum molecular sampling to identify its phylogenetic position within Gomphrena genus and to perform a multivariate analysis to objectively differentiate taxa based on morphological characters. The ITS and trnL-F regions were analyzed individually and combined using Bayesian inference and maximum parsimony methods. To analyze the morphological characters we performed a clustering method (partitioning around medoids with the Gower’s dissimilarity algorithm). The molecular analyses supported the monophyly of the G. meyeniana complex but did not support segregation into varieties. The morphological analyses gathered the infra-specific taxa into only three varieties that can be easily distinguished through three simple characters: the presence of leaves on the flowering shoot, the habit of the flowering shoot, and the pilosity of the tepals. The varieties of G. meyeniana accepted here are var. meyeniana, var. caulescens, and var. flaccida. A dichotomous key to identify the infra-specific taxa is here presented and illustrated. The varieties tucumanensis, and conwayi were synonymized with var. caulescens, and var. meyeniana respectively.

The recently resurrected monotypic genus Monrosia (Polygalaceae) is endemic to the Argentinian provinces of Catamarca to San Juan in the southern Andes. We here describe and illustrate Monrosia sanjuanensis, a new species endemic to the Province of San Juan and the second species of the genus, and revise the genus. Monrosia and its two species are described and analysed in a phylogenetic context, using nuclear and chloroplast DNA sequences. A distribution map, illustration, photos of the morphological structures of the two species, and taxonomic key are provided. We designate a lectotype for the name M. pterolopha.