Palicourea and related genera were included until very recently in the tribe Psychotrieae, and are still included in that tribe by some authors (e.g., Bremer & Eriksson 2009). This group, as either the large tribe Psychotrieae s. lat. or as two separate tribes, includes about 24% of the species of Rubiaceae (Razafimandimbison et al. 2014). Psychotrieae belongs to the subfamily Rubioideae and has been diagnosed by raphides in the tissues, generally terminal inflorescences, valvate corolla aestivation, ovaries with a single erect basal ovule in each locule, generally fleshy fruits, seeds that are individually enclosed in pyrenes formed from the endocarp, and starchy endosperm (Robbrecht, 1988). Robbrecht & Manen (2006) in a meta-analysis of Rubiaceae genera based on molecular data recovered two clades within Psychotrieae s. lat., and recognized these as two separate tribes, Psychotrieae and Paliocureeae. They separated Palicoureeae based on this molecular data and diagnosed it by its usually persistent stipules, pyrenes generally with preformed germination slits, and seeds with a thin seed coat that lacks red pigments; vs. usually caducous stipules, pyenes mostly without preformed germination slits, and seeds with a thicker seed coat with alcohol-soluble red pigments in Psychotrieae. These two groups were also recovered and recognized as two tribes by Razafimandimbison et al. (2014), who noted another chemical difference between these, with Palicoureeae characterized by cyclotides that are apparently absent in Psychotrieae. Both clades or tribes are pantropical, but Psychotrieae is more diverse in the Paleotropics while Palicoureeae is more diverse in the Neotropics.

Berger & Schinnerl (2019) detailed some of the chemistry of secondary metabolites in this group, in Psychotria s. str., Palicourea s. lat., and other genera of Palicoureeae, and found chemical differences between Psychotria, which lacks alkaloids and contains tannins, and the genera of Palicoureeae, with some characteristic types of alkaloids and without tannins. They noted that the DMT of Psychotria viridis is so far the only alkaloid documented from this genus in its current circumscription, although they also noted that the genus has not been extensively sampled.

The genera currently included in the Palicoureeae are all tropical, and are mostly restricted to either the Old World or the New World tropics. Two genera are known to be pantropical: Geophila D. Don, with ca. 25 species of prostrate herbs, and Margaritopsis Griseb. or Eumachia DC., with ca. 100 species of shrubs and small trees [the name Eumachia has recently (Dec 2014) been formally accepted to have priority over Margaritopsis but most species do not have combinations in that genus yet]. Paleotropical genera of Palicoureeae are Chassalia Comm. ex Poir., with ca. 80 species found from Africa through Asia; Hymenocoleus Robbr., with ca. 10 species of creeping herbs found in Africa; and Puffia Razafim. & B. Bremer, with 1 species similar to Hymenocoleus but found in Madagascar. Neotropical genera of Palicoureeae are Palicourea Aubl., with ca. 600 species of shrubs, small trees, and a few creeping herbs; Carapichea Aubl., with ca. 25 species of shrubs and small trees; Notopleura (Benth.) Bremek., with ca. 100 species of succulent herbs, subshrubs, and epiphytes; and Rudgea Salisb., with ca. 120 species of shrubs and small trees. Some other small, poorly known, Neotropical genera with dry fruits from the Guayana Highlands in notheastern South America have also been included with these genera, but probably are not closely related although their actual relationships are unknown (Taylor, 1996), Aphanocarpus Steyerm. with 1 species and Coryphyothamnus Steyerm. also with 1 species. Several other genera have been included in Psychotrieae s. lat. but are now excluded, including Pagameopsis (Standl.) Steyerm. (Piesschaert et al., 2001) and Ronabea Aubl. (Taylor, 2004). The circumscription of Palicourea is currently problematic, because this clade includes a number of species that have been included in Psychotria until recently based on different diagnoses of these genera than used today (Taylor, 1996; Taylor, 2015). The circumscription of Carapichea (Taylor & Gereau, 2013) is provisional and needs further study. The species described in traditional Psychotria from the Pacific Islands have not been surveyed thoroughly and probably a number of those also belong to Eumachia.

Most Palicoureeae are shrubs but there are creeping herbs with roots at the nodes in several genera. Stipule form varies widely, from interpetiolar to fused around the stem, and triangular, multifid, or usually bilobed. The stipules are variously persistent with the leaves, to deciduous by fragmentation with the basal portion generally remaining. In several genera the stipules characteristically become hardened and usually yellowed with age (e.g., Margaritopsis, Carapichea). The stipules of most Rubiaceae have glandular colleters internallly, between the stipule and the stem, that function as the stems grow and then dry up; in many species of Palicoureeae, there are also well developed colleters or glands borne variously on the tips of the stipule lobes or segments, along the stipule margins, medially on the stipule sheath, and/or adaxially between the stipule and the stem. These glands have been noted for some genera (e.g., Chassalia, Rudgea but overlooked in others. However stipules borne on various marginal or abaxial (i.e., external) positions are apprently present in species of most if not all the genera. The inflorescences in Palicoureeae are generally terminal, with the genera with axillary inflorescences now excluded from this tribe (Ronabea, Taylor 2004; Coccochondra, Taylor 2004). Some species still included appear to have axillary inflorescences, but these are here interpreted as terminal on short axillary shoots as in species of Ixora [e.g., Palicourea sessilis (Vell.) C.M. Tayor]. The terminal inflorescences are often displaced to pseudoaxillary (sensu Robbrecht 1988: p. 68) by subsequent growth of stems from one of the axillary buds that subtends the inflorescences, and Notopleura subg. Notopleura the inflorescences are consistently pseudoaxillary and borne below the apical node. The flowers are mostly 5-merous but a number of species are 5-merous, and the vast majority of the species are distylous. The calyx limb is usually developed and regularly lobed, though it may occasionally be fused and calyptrate (e.g., Palicourea spathacea. The corollas vary widely in color and form, and are pollinated by insects, both diurnal and nocturnal, and in the Neotropics also by birds. The corollas often have a horn-like appendage or thickening on the abaxial surface of each corolla lobe. The stigmas are linear and equal in number to the ovary locules, which are usually 2 but occasionally 4-5. The fruits are fleshy to succulent and indehiscent, and variously white, red, orange, purple, blue, or black when mature. The pyrenes vary widely in form of the pyrene walls and the preformed germination slits (GPGS's); these were surveyed in detail by Piesschaert (2001).

Author: C.M. Taylor
The content of this web page was last revised on 7 May 2021.
Taylor web page: http://www.mobot.org/MOBOT/Research/curators/taylor.shtml

• Razafimandimbison, S. G., C. M. Taylor, N. Wikström, T. Pailler, A. Khodabandeh & B. Bremer. 2014. Phylogeny and generic limits in the sister tribes Psychotrieae and Palicoureeae (Rubiaceae): Evolution of schizocarps in Psychotria and origins of bacterial leaf nodules of the Malagasy species. Amer. J. Bot. 107(1): 1102–1126.
• Bremer, B. & T. Eriksson. 2009. Time tree of Rubiaceae: Phylogeny and dating the family, subfamilies, and tribes. Int. J. Pl. Sci. 170(6): 766–793.
• Robbrecht, E. & J. F. Manen. 2006. The major evolutionary lineages of the coffee family (Rubiaceae, angiosperms). Combined analysis (nDNA and cpDNA) to inferthe position of Coptosapelta and Luculia, and supertree construction based on rbcL, rps16, trnL-trnF and atpB-rbcL data. A new classification in two subfamilies, Cinchonoideae and Rubioideae. Syst. & Geogr. Pl. 76: 85–146.
• Taylor, C. M. 1996. Overview of the Psychotrieae (Rubiaceae) in the Neotropics. Opera Bot. Belg. 7: 261–270.
• Taylor, C. M. 2014 [2015]. Rubiacearum americanarum magna hama XXXIII: The new group Palicourea sect. Didymocarpae with four new species and two new subspecies (Palicoureeae). Novon 23(4): 452–478.
• Piesschaert, F., S. Jansen, I. Jaimes, E. Robbrecht & E. Smets. 2001 [2002]. Morphology, anatomy, and taxonomic position of Pagameopsis (Rubiaceae–Rubioideae). Brittonia 53(4): 490–504.
• Taylor, C. M. 2004. The neotropical genus Ronabea (Rubiaceae, Lasiantheae). Syst. & Geogr. Pl. 74(1): 35–42.
• Taylor, C. M. 2011. The genus Coccochondra (neotropical Rubiaceae) expanded. Pl. Ecol. Evol. 144(1): 115–118.
• Piesschaert, F. 2001. Carpology and Pollen Morphology of the Psychotrieae (Rubiaceae-Rubioideae). Ph.D. Dissertation, Catholic University of Leuven, Belgium.
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Notes
1. The name Cephaelis Sw. is a synonym of Palicourea in its current, broader circumscription. The genus Cephaelis as it was long recognized was diagnosed only by a capitate inflorescence with well developed bracts, a form that has arisen several times in the Psychotrieae and Palicoureeae as well as other tribes so in practice Cephaelis was extensively polyphyletic.

2. The name Uragoga Baill. was considered by Baillon to be an older name for Cephaelis, but it is not older and most of the other genus names in this tribe have priority over this name (Talor & Gereau, 2013). The name Uragoga was used, however, by both Baillon and Kuntze for a very broadly circumscribed genus that included essentially all of the tribe Palicoureeae plus several genera now classified in other tribes; this taxonomy was not accepted by subsequent authors.

3. The small genera Gamotopea Bremek., Naletonia Bremek., Nonatelia Bremek., and Petagomoa Bremek. were separated by Bremekamp from Palicourea, but considered synonyms of it by subsequent authors.

4. The genus Stempelia A. Rich. has been synonymized with Rudgea.

5. The genus Montamans Dwyer is now considered a synonym of Notopleura subg. Notopleura.

6. The names Chytropsia Bremek., Readea Gillespie, and Chazaliella E.M.A. Petit & Verdc. are now considered synonyms of Margaritopsis (Razafimandimbison et al. 2014). The name Eumachia DC. was recently shown to be an older name for this genus, and the name Margaritopsis was proposed for conservation over Eumachia but this proposal was rejected by the Nomenclature Committee (Applequist, Taxon 63: 1358-1371).

7. The genus Stachyococcus Standl. was synonymized with Carapichea by Taylor & Gereau (2013).

8. The genus Margaritopsis C. Wright is now synonymized with Eumachia DC.