The genus Apomuria was described by Bremekamp (1963) in his studies of the Psychotrieae in Madagascar and the Comores. Although he noted that several species from East Africa also belong to this group, only species of the Comores and Madagascar were formally included. Apomuria comprised a set of species that Bremekamp separated from Psychotria s. str. based on seed characters. Bremekamp's genus-level taxonomy of the Psychotrieae in this region differed from that of other authors, in particular it separated the species of Psychotria s. str. (sensu Petit, 1964, and Andersson, 2002) into several genera based on some particular seed characters, and used the Neotropical name Mapouria Aubl. for one of these segregate Madagascar genera. Bremekamp considered Apomuria to be related to his Mapouria, and its name is an anagram intended to indicate this relationship. Apomuria was separated based on its thin-walled pyrenes that are flat (i.e., not furrowed and not crested) adaxially and its seeds with the endosperm not ruminate but also not entire, but with a deep T-shaped adaxial invagination; in contrast to seeds with no adaxial furrow or with a pair of longitudinal adaxial furrows, and/or with ruminate endosperm in Psychotria and Bremekamp's other Psychotrieae genera. Pyrene and seed characters are of significance in drupaceous Rubiaceae, however as documented by Petit (1964) and Piesschaert (2001: 327-328) the seed characters that diagnose Apomuria are in fact variable within groups of related Psychotria species. Thus the group of species diagnosed as Apomuria by these characters is heterogeneous, though several of the species do appear to be related to each other. The species described in Apomuria are often similar to species included in Mapouria by Bremekamp (1963), and both of Bremekamp's genera have the characters of Psychotria s. str. and apparently should be included within that genus based on morphology. This question was addressed with molecular data by Razafimandimbison et al. (2014), who found the Madagascar species of Mapouria included in Psychotria as generally accepted. They also found the species of Apomuria distributed on several different clades within Psychotria and thus not only part of Psychotria, but in some cases more closely related to species that Bremekamp classified in Psychotria than to other species he included in Apomuria. The Paleotropical species that Bremekamp described in Mapouria were transferred nomenclaturally to Psychotria by Davis et al. (2007), and the species described in Apomuria by Razafimandimbison et al. (2014).
The species Bremekamp included in Apomuria were characterized by him as having, in addition to the diagnostic seed and pyrene characters, leaves without domatia and with the tertiary venation hard to see; bilobed caducous stipules; terminal, pedunculate, cymose inflorescences with reduced bracts; pedicellate, 4- or 5-merous, distylous flowers; white or greenish white corollas with a ring of pubescence at the stamen insertion; red fruits; and thin-walled pyrenes that are smooth or occasionally costate. Additionally these species have stem nodes with the interpetiolar fringe of persistent ferrugineous pubescence that characterizes Psychotria s. str. (CMT pers. obs.), and most (though not all) of the Apomuria species dry with a green or gray-green color. Bremekamp's statement that Apomuria species lack domatia apparently refers to well developed crypt-type acarodomatia, because several species do have well developed pubescent domatia in the abaxial vein axils of the leaves, and sometimes these species also have flanges developed along the veins that probably function as acarodomatia. Bremekamp stated that only Apomuria punctata has bacterial nodules in the leaves, but actually Apomuria bullata also has these, though they are few, large, and easily overlooked (but visible on the images of the type material). Bremekamp's description of the tertiary venation as poorly developed applies to most of the species, but some do have abaxially well developed though plane tertiary venation. His description of the corollas as white and the fruits as red may be accurate, but the flowers or fruits of several Apomuria species are not yet documented.
Bremekamp included in Apomuria what seem to be several distinct species or species groups, and he distinguished the species mainly by leaf and pubescence characters and described in this genus several species for which the pyrene and seed characters are unknown. Bremekamp noted that several species of Psychotria subg. Tetramerae from East Africa with bacterial nodules in the leaves and thin-walled pyrenes belong in Apomuria, and provided a validly published name for one of these, Apomuria punctata. He excluded the members of Subg. Tetramerae with thick-walled pyrenes, however Piesschaert (2001) concluded that there is continuous variation in this feature within this subgenus so no distinct species groups can be separated by pyrene wall thickness. The species with the combination of bacterial nodules, a green drying color, and an African distribution (with one dispersal to the Comores) appear to be distinct from the other Apomuria species. Apomuria bullata also appears to differ from the other Apomuria species. This has narrow bullate leaves with scattered lobed bacterial nodules, a dark brown drying color, a pendulous terminal inflorescence that is quickly displaced to pseudoaxillary, hemispherical pyrenes in a subglobose fruit, and a habit in humid vegetation. This species is similar in aspect, habitat, and several unusual characters to the other Madagascar species of Psychotria with bacterial nodules, which Bremekamp (1960) included in their own informal group and Piesschaert (2001) considered different from the species of Subg. Tetramerae; thus Apomuria bullata is probably more closely related to these species than to other Apomurias. And, Apomuria moramangensis differs from the other Apomuria species in its quite short inflorescence, rather small leaves that are shiny on both surfaces, hemispherical pyrenes in an ellipsoid fruit, and habitat in humid vegetation; this species is quite similar in aspect to several Psychotria species found in its type region, and seems more closely related to those than to the other Apomuria species.
The remaining species of "core" Apomuria share thin-textured, matte (i.e., not shiny) leaves; thin-textured stipules with the lobes usually aciculate to filamentous at the tips; few- to several-flowered corymbiform inflorescences with one pair of secondary axes that are longer than the primary axis, and subglobose pyrenes that form didymous fruits (when both pyrenes develop; in the species for which the fruits are known). Except for Apomuria parvifolia these species are found in dry vegetation and appear to be deciduous. Two species groups can be approximately separated within this "core" group, with two species intermediate between them. One group includes Apomuria biloba, Apomuria melanostichta, and Apomuria mollis and is characterized by relatively large, obovate to broadly elliptic or suborbicular leaves that are usually emarginate to retuse at the apex. Apomuria biloba is in fact notable for its deeply retuse leaves, and the species name refers to these bilobed leaves. The other species group includes Apomuria angustifolia, Apomuria crispulifolia, Apomuria parvifolia, Apomuria pendulifolia, and Apomuria perrieri, and is characterized by small to medium-sized elliptic, narrowly elliptic, or oblanceolate leaves that are acute to acuminate at the apex. Bremekamp recognized several varieties of some of these species based entirely on variation in pubescence density and distribution. Most or all of these species appear to be related and these may not all be distinct, except for Apomuria angustifolia. The type of Apomuria angustifolia (i.e., var. angustifolia) differs from the other "core" Apomurias in its pyramidal, well-developed, many-flowered inflorescences with the primary axis longer than the secondary axes, and several pairs of secondary axes. However the type of Apomuria angusifolia var. pubescens is similar to the other Apomuria species of this group, and whether these two plants are conspecific is in need of reevaluation. Intermediate between these species groups are Apomuria falcata and Apomuria hymenodes, with medium-sized elliptic to obovate leaves that are rounded to obtuse or acute at the apex.
The species Bremekamp included in Apomuria are similar in aspect to, and frequently confused with: Triainolepis, which differs in its ovaries with 2 ovules in each locule and subglobose multilocular fruits; the species Bremekamp included in Pyragra, which differs in its ovate, flattened, schizocarpous fruits with carpophores that persist after the mericarps have fallen; and some species that Bremekamp included in Cremocarpon, which have ellipsoid schizocarpous fruits that also have persistent carpophores. Also similar to some Apomuria species are several Psychotria species, which differ in their yellow corollas and fruits that become white then blue or black; particularly similar here are Psychotria boenyana and Psychotria rubropedicellata.
For more information on individual species and synonymy, see the Madagascar Project. (To access that data, in the upper right of this web screen, click on "Choose Project", and then the corresponding database from that list.)
Author: C.M. Taylor. The content of this web page was last revised on 31 July 2014.
Taylor web page: http://www.mobot.org/MOBOT/Research/curators/taylor.shtml