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Published In: Linnaea 4: 4. 1829. (Jan 1829) (Linnaea) Name publication detailView in BotanicusView in Biodiversity Heritage Library

Project Name Data (Last Modified On 4/28/2015)
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Psychotria L., Palicourea Aubl., and several 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.

Psychotria has long been recognized as closely related to a number of smaller genera, and these were all synonymized by Razafimandimbison et al. (2014) so that the tribe Psychotrieae comprises the single genus Psychotria. This single evolutionary lineage probably comprises 1000 or more species has an unusually extensive morphological variation. Apparently all the species are perennil, have inferior ovaries and opposite leaves, and do share the characters noted for the tribe; also, specimens of Psychotria characteristcally dry with a gray, dark bray, or reddish brown color. Beyond this however there is extensive variation in most morphological features, including habit, symbioses with other oganisms, inflorescence arrangement, and flower and fruit size and form. Psychotria includes a number of epiphytic species in Asia, some of which house ants within their swollen stems; these myrmecophilous epiphytes have been separated at times in Hydnophytum Jack, Myrmecodia Jack, Myrmedoma Becc., Myrmephytum Becc., and Squamellaria Becc. Several species from the Neotropics and Asia (e.g., Amaracarpus Blume) have the branches and leaves arranged in a planar orientation, with these leave often rather small. Several other species in the Neotropics, Africa, and Madagascar have a "trash-bucket" habit, with relatively large subsessile leaves and large stipules tha trap falling detitritus along the stem and adventitious roots that absorb nutrients from this decaying detritus. Some species of Psychotria in Africa and Madagascar have nodules in their leaves that contain nitrogen-producing bacteria; these unusual species have been considered a single evolutionary group, Psychotria subg. Tetramerae Hiern, but this symbiosis has apparently arisen more than once in the genus (Razafimandimbison et al., 2014). Occasional species have markedly regularly anisophyllous leaves. Stipule form varies from interpetiolar and triangular to usually bilobed, to fused around the stem into a tube or sheath, to fully fused into a calyptrate sheath.

Psychotria also has wide variation in reproductive structures. The inflorescence arrangement varies similarly to other Rubiaceae lineage, with the inflorescences terminal and basically cymose, but range from sessile to pedunculate and variously are branched with reduced to developed bracts, to capitate and enclosed by well developed involucral bracts. Plants with capitate bracteate heads have been classified in Cephaelis Sw., which is a synonym of Palicourea, and Megalopus K. Schum., which is a synonym of Psychotria; modern studies have shown that the distinctive capitate inflorescence enclosed by large involucral bracts has arisen several times within both Psychotrieae and Palicoureeae. Some species of Psychotria from Asia have consistently pseudoaxillary inflorescences (e.g., the formerly recognized genus Amaracarpus). Some species of Psychotria from Madagascar appear to have axillary inflorescences, with the flowers borne in short subsessile groups produced in both axils of the node, but these inflorescences were interpreted by Bremekamp (1963) as terminal inflorescences borne on short axillary shoots (i.e., brachyblasts) similarly to inflorescences of Ixora. The flowers appear to last for one day, and be protandrous. The flowers of the majority of species are distylous, with some isostylous populations found in distylous species or perhaps a few isostylous species; however some species of the Pacific Islands are dioecious or perhaps polygamodioecious. The corollas are generally white to cream, but are bright yellow to orange in group of species in Madagascar ("Mapouria" of Bremekamp 1963).

The fruits are generally fleshy and red at maturity, or white or black in some species from Madagascar. The pyrenes are generally entire, that is without pre-formed germination slits (Piesschaert 2001), but slits are present in various species (e.g., the formerly recognized genus Amaracarpus; Davis & Bridson 2004). Most species have two ovary locules, stigmas, and pyrenes, but several species from the Indian Ocean region have three to five stigmas, locules, and pyrenes and were separated into Psathura Comm. ex Juss. The endosperm various from entire to deeply ruminate, and this feature was used to diagnose separate groups within Psychotria by Petit (1964) and Bremekamp (1963); however this character appears to vary within lineages. The fruits of Psychotria are generally fleshy and indehiscent, but dry schizocarpous fruits with well developed carpophores have arisen several times in this lineage (Razafimandimbison). The carphophores apparently are formed by fibrous structures that are visible in the fleshy fruits of various species (Piesschaert, 2001), and range from rather small to quite large. Several Psychotria species from Madagascar and New Caledonia with dry ellipsoid mericarps were separated in Cremocarpon Bremek., however molecular data find that this species group is polyphyletic. Several other species from Madagascar grow in dry habitats and have flattened, sometimes thinly winged mericarps, and these were included variously in Pyragra Bremek. and Cremocarpon.

Psychotria (and thus Psychotrieae) has not been studied across its range, but several regional taxonomic treatments cover many of the species. In particular see Petit (Bull. Jard. Bot. Belgique 1964, 1964) and Verdcourt (Flora of East Tropical Africa, Flora Zambesiaca) for the African species; Bremekamp (1963) for those of Madagascar; Sohmer & Davis (2007) for species of the Philippines; Deb & Gangopadhyay (J. Econ. Taxon. Bot. 1989) for species of India; Hamilton (1989, in three parts), Steyermark (Flora of Venezuela), and Taylor (various works) for Neotropical species. The type of the genus was based on mixed elements, from Jamaica in the Neotropics and Asia; the identity of the type species Psychotria asiatica L. was clarified by Davis et al. (2001). For more detail see the page for Psychotria.

Author: C.M. Taylor
The content of this web page was last revised on 28 April 2015.
Taylor web page: http://www.mobot.org/MOBOT/Research/curators/taylor.shtml

Taxa Included Here: The genus name Mapouria is a synonym of Psychotria. The identity of this name has long been confused based in part on differing circumscriptions of Psychotria, and in part on unorthodox usage of the name Mapouria by Bremekamp (1963).

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