Sabicea includes ca. 150 species of mostly spreading and twining climbers that are found widely in disturbed vegetation in the Neotropics, Africa, and Madagascar. Most of the species and morphological variation are found in Africa (ca. 100 species), but the Neotropics has about a third of the species and these are distributed in various habitats (Khan, 2007; Taylor et al., 2004; Zemagho et al., 2016). In general, Sabicea is distinctive in its usually interpetiolar, flat, ligulate to obovate stipules, axillary or pseudoaxillary cymose inflorescences, salverform white (in the Neotropics) corollas, red to purple berry-like fruits with five (in the Neotropics) locules, and habitat usually in open disturbed sites in wet lowland vegetation. Some African species are erect shrubs, and some have pectinate stipules, flagelliform inflorescences, bilocular ovaries, and/or subcapitate, involucrate inflorescences. The stipules throughout the genus are characteristically (though not always) obtuse to rounded at the top and reflexed; this stipule form together with a climbing habit are only found otherwise in Uncaria, which differs in its spines. A few Neotropical species of Sabicea are found in seasonal habitats in Brazil, where they grow as weakly to fully erect geofrutices in fire-dominated ecosystems (e.g., Sabicea humilis; Zemagho et al., 2016, appear to have overlooked these in their morphological characterization of Subg. Sabicea), and these species are sometimes not recognized as Sabicea because they lack an extensively vining habit. A number of Sabicea species are distinctive in having arachnoid or canescent, whitened pubescence, and the presence of such pubescence is often a species-level character. The fruits are black at maturity and then are quickly removed by frugivores, but the purple immature fruits are soft and often mistaken for the mature color.
Molecular study of Sabicea (Khan et al., 2008; Zemago et al., 2016) found the Neotropical species analyzed grouped in a single lineage that was derived within the genus. Zemagho et al. recognized four subgenera; the Neotropical species were all grouped in their study with most of the African and all of the Malagasy species in Subg. Sabicea. Zemagho et al. significantly broadened the circumscription of Sabicea in Africa to include several previously-separated genera (notably Stipularia, Ecpoma, Pseudosabicea), while in the Neotropics its circumscription has been narrowed a bit through the separation of Amphidasya.
Sabicea is today included in the Tribe Sabiceeae, which has been separated (or narrowed) rather recently based mainly on molecular analysis (Khan 2008; Bremer & Eriksson, 2009; Zemagho et al., 2016), and removed from a complex group of genera in the broadly circumscribed, morphologically variable, traditional Mussaendeae or later the Isertieae. Subsequently the Sabiceeae tribe was broadened a bit to include the three genera of the briefly recognized Virectarieae (Khan, 2008). See Zemagho et al. (2016: 569) for a key to the genera of Sabiceeae, which differ from each other markedly in habit, inflorescence position, fruit type, habitat, and range.
Sabicea has been studied recently in detail for Africa by Zemagho and collaborators, but in the Neotropics it has as only been reviewed recently by Khan (2007), who outlined a partially new, well documented taxonomy with several new species but unfortunately has not yet published that treatment. The Neotropical species were also studied taxonomically in detail earlier by Wernham (1914), and several of his species have now been synonymized but his treatment is useful for identification.Sabicea was reported to be consistently distylous by Zemagho et al. (2016), but Neotropical Sabicea has been characterized as having variously homostylous and distylous species (Khan, 2007). A few species have been confirmed to be distylous (Sabicea panamensis, Andersson 1994; Sabicea cinerea, Teixeira & Machado, 2004, however Khan, 2007, treated the all the pubesccent plants from their study region as Sabicea grisea; several additional species, Khan, 2007), but the floral biology of most of the Neotropical species has not been studied.
In the Neotropics, Sabicea has centers of diversity in northern and northeastern South America; see Steyermark (1974) and Taylor et al. (2004) for floristic treatments, and also in the Andes. Steyermark separated species based in part on pubescence details, including both the distinctive white-pannose pubescence found on some species and also the orientation, size, and form of the trichomes on the outside of the corolla, as well as the degree of lobing of the calyx limb. The calyx limbs appear to be more variable than he noted in some species, and the systematic consistency of the corolla pubescence may be more variable than he saw. Sabicea panamensis and Sabicea villosa are the most widespread and commonly encountered Neotropical species.
The description here applies to the generic characters of Neotropical Sabicea, and the literature citations and synonymy focus on this region but are not at all comprehensive for either the genus here or all the Neotropical species. The web page here basically summarizes the available published information for the Neotropical species that does not conflict with the unpublished conclusion of Khan (2007). The Sabicea species of Madagascar are treated on that project's web page, but a few species from there and Africa are also linked on this page due to overlapping studies.
Author: C.M. Taylor, with courteous help from S.A. Khan.
The content of this web page is under construction, and was last revised on 3 October 2020.
Taylor web page: http://www.mobot.org/MOBOT/Research/curators/taylor.shtml