Most of the plants that were treated in the Flora Mesoamericana (Davidse et al., 2012) as Hoffmannia discolor were included in the newly described species Hoffmannia rzedowskiana by Castillo-Campos et al. (2014). In the Flora Mesoamericana treatment, the name Hoffmannia discolor was accepted with a rather general description, which could apply to most of the understory, short-stemmed, velvety-leaved Hoffmannias in Central America, and the name Hoffmannia refulgens was cited as a synonym of Hoffmannia discolor. Borhidi in his Rubiaceae flora of Mexico (2012) considered these two different species, although their descriptions were quite similar and the description there of Hoffmannia refulgens was basically copied from the protologue and incomplete for comparison with the modern species of Hoffmannia. Borhidi also noted there that these two species may not be distinct. Castillo-Campos et al. described Hoffmannia rzedowskiana based on extensive study of the plants in the field and cultivation in a common garden to document the variation, and concluded that their plants represent s a distinct species by contrasting these plants with Hoffmannia discolor and a species similar to that, Hoffmannia bullata. They did not compare their new species to Hoffmannia refulgens, even though Hoffmannia refulgens is considered by recent authors to be from Mexico and closely related to Hoffmannia discolor, and even though their new species keys out directly to Hoffmannia refulgens in Borhidi's Mexican Rubiaceae treatment. No differences are evident between the Mexican plants of Hoffmannia rzedowskiana and Hoffmannia refulgens, and these are here considered synonyms; the discussion and table presented by Castillo-Campos et al. here clarify for the first time the separate species status of Hoffmannia discolor and Hoffmannia refulgens, and their identities and differences. The plants from Nicaragua that they included in Hoffmannia rzedowskiana however match the characters they note for of Hoffmannia bullata rather than the Mexican plants they cited.
The study by Castillo-Campos et al. (2014) is significant in its careful examination and documentation of the variation within a species of Hoffmannia (cf. in particular Fig. 2 and the discussion on p. 40). Many species of Hoffmannia are unusually variable in vegetative and flower features, most strikingly in the uniform green vs. dark green veins of the leaves, found on different plants, and the range of size and color in the corollas. This is the first study that documents the range of this variation, and the common garden experiment begins documentation of its basis. Similar variation is found in understory species of other Rubiaceae genera (e.g., Psychotria), and has not been studied but likely shows a similar pattern to the one documented here in some cases though in some species, the dark leaves with white veins appears to characterize juvenile plants vs. uniform green leaves on reproductive stems.