La circunscripsión de Palicourea subgen. Heteropsychotria (Rubiaceae Palicoureeae)
Authors: Borhidi A. L. 
Published: March 2017

The subgenus Heteropsychotria was detected and described by Julian Steyermark in the frame of the monographic series of the Botany of the Guyana Highland (Steyermark 1972) and repeatedly in a more illustrated version in the Flora of Venezuela (Steyermark 1974). Within the subgenus he distinguished 13 sections and 31 series. Three sections (Nrs 4, 7 and 11) of the 13 remained without names and descriptions. After the fundamental molecular taxonomic study of Nepokroeff et al. (1999) a publishing activity started producing a number of critical studies separating some sections as valid individual genera. The section Chytropsia has been included into the genus Margaritopsis Ch. Wright (Andersson 2001, Taylor 2005). The section Notopleura regained its generic status according to Bremekamp’s original concept (Taylor 2001). The Mapouria section has been eliminated by the re-establishment of the Carapichea genus (Andersson 2002b, Taylor and Gereau 2013). It has been recently recognised, that the greater part of the species classified by Steyermark into the section Durifolia belongs to the expanded genus Coccochondra (Taylor 2011). The re-consideration of the taxonomic position of the slenderized subgenus Heteropsychotria was begun by C. M. Taylor et al. with the transfer of some Mesoamerican species as late as 2010, although their close relation to the genus Palicourea was emphasised by Nepokroeff et al. (1999). The next step is, that for the second edition of the Rubiáceas de México the Mexican species of Heteropsychotria were transferred into Palicourea (Borhidi 2011), while C. M. Taylor maintained the Mesoamerican ones within the frame of Psychotria (Taylor 2012). Recently C. M. Taylor started to revise the taxonomic position of the South American Heteropsychotria species with a new circumscription and re-description of the section Didymocarpae (Taylor 2014) by the distinction and description of the new section Tricephalium (Taylor 2015) separating from the rest of the section Cephaëlis and by the detailed elaboration of the section Nonatelia in a new concept with enlarged frame (Taylor and Hollowell 2016). For the remained parts of the Steyermark’s system we suggest here the following reconsiderations. The section Heteropsychotria is enlarged by the inclusion of the anonymous section 4 of Steyermark. The greater part of the anonymous section 7, which remained after the exclusion of the Carapichea species, is described as a new section Bracteiflorae with Palicourea caerulea as type. The section Nonatelia is reconsidered and reshaped in a considerably enlarged form by Taylor and Hollowell (2016), while the section Potaroenses remains unchanged. The Pseudocephaëlis section remains without the series Appunianae, which has been included into the section Tricephalium C. M. Taylor. The section Cephaëlis of Steyermark is divided into two sections. The species with terminal, mostly pedunculate inflorescences is separated under a new name Neocephaëlis Borhidi with Palicourea tomentosa (Aubl.) Borhidi, selected as the type species of the section. The other section includes the species of axillary, mostly sessile inflorescences, elevating the series Axillares of Steyermark on section rank and expanding it by the inclusion of the anonymous section 11, with Palicourea axillaris (Aubl.) Borhidi, selected as the type. For the rest of the eliminated Durifolia section a new one is created under the name Cordifoliae Borhidi, while the Oppositiflorae section also must be cancelled, because its type species is Ronabea latifolia Aubl. At last a new section Microphyllae Borhidi is established for the small-leaved xero-tolerant species of the Antilles with Palicourea orientensis Borhidi et Oviedo as type. The review includes more than 220 species.
Recently Taylor has made an attempt to eliminate the subgenus Heteropsychotria Steyerm. and identified it as a synonym of subgenus Palicourea. It cannot be accepted because the two subgenera differ from each other in important morphological and physiological characters.
The subgenus Palicourea is characterised by having brightly coloured odourless, mostly pedicellate and separated flowers with large corollas often curved tube and swollen base containing an appreciable quantity of nectar, protected by a ring of stiff hairs, namely an arranged complex of characters, which are adapted for hummingbird-pollination. The type species is Palicourea guianensis Aubl. In contrast, the subgenus Heteropsychotria is characterised by having generally green to white inflorescences with white greenish or pale yellow fragrance, smaller mostly sessile flowers with corollas of straight short tube without swollen base and inner hairy ring, but with different pubescence in/or above the middle of the inner face of the tube. These arranged set of characters are clearly adapted to the insect-pollination. The type species is Palicourea deflexa (Sw.) Borhidi. Taylor refers to a great variation in some separate characters between the two character complexes presented in the Flora of the Venezuelan Guayana (2004) without mentioning any concrete example. The reality is, that between the two character complexes there is no intermediate taxon.
After having replaced the subgenus Heteropsychotria Steyermark synonymised by Taylor, a new section has been introduced and created, the section Tricephalium (Müll. Arg.) C. M. Taylor, comprising 35 species and classified in Palicourea subgenus Montanae Taylor 1997. It is diagnosed by having “thick-textured leaves with well-developed intersecondary veins that are extensively reticulated and inflorescences with the flowers sessile in small to large heads that are enclosed by well-developed bracts and the fruits pass through a yellow to red immature stage”. Additionally the section is also characterised by stipules that are shortly united around the stem to laminar, bilobed to emarginate, rounded, rounded and denticulate or erose in each side.
Really, the section Tricephalium is problematic in some respect. It is heterogeneous as a taxonomic unit, because it has not a standard set of characters, even not one character existing in all species classified here for the distinction of the whole group. The most common characteristic feature is the texture and venation of the leaves, a vegetative character that may be influenced rather easily by ecological conditions. Moreover, the major part of the species lives in montane valleys of the Andes of Colombia, Ecuador, Peru and Bolivia as isolated local endemics within similar montane habitats. It is unknown, how these characters would react if the individuals of these species got into lowland situation (see: Clausen et al. (1948) on Achillea lanuginosa). It is to be mentioned that similar leaf texture venations occur in some Carapichea and Coccochondra species as well. Another weakness of the section is the superfluous selection of the typical species, the Palicourea triadica (Müll. Arg.) C. M. Taylor being a very scarcely collected and poorly known species is unable to represent a species-rich, diverse section. After a thorough comparative analysis of the descriptions it turns out that the only character combination occurring in every species of the section Tricephalium is the character-set of the subgenus Heteropsychotria. The only exception would be the Palicourea neilii C. M. Taylor that has according the description bright yellow flowers and corolla tube swollen and bent at the base, but in his fig. 1F the corolla tube is straight and narrow at the base. Therefore we get to the conclusion that the section Tricephalium C. M. Taylor is treated here unchanged as a whole, not in the subgenus Montanae C. M. Taylor, but accentuated its taxonomic position in the frame of the subgenus Heteropsychotria Steyerm.