Augusta includes four species of rather short, tough-stemmed shrubs with rather narrow leaves, and these plants have a distinctive habit: they grow along the edges of streams and rivers where they are rooted in and often covered by moving water and are presumably dispersed by water (rheophytes). Augusta has triangular interpetiolar stipules, one to a half dozen or so homostylous flowers in a short terminal cyme, large showy corollas with slender tubes and convolute lobes, and rather woody short septicidal capsules with numerous angled seeds. Augusta also has an unusual disjunct distribution, and today includes what were formerly two genera: Augusta (including plants sometimes called Ucriana) from southeastern Brazil, with tubular-funnelform red flowers that are presumably pollinated by hummingbirds, and Lindenia, with one Central American and two Pacific island species and salverform white corollas that are presumably pollinated by hawkmoths. Kirkbride (1997) analyzed these four species and concluded that they belong in the same genus, which has a marked diversity in pollination mode and for which Augusta is the oldest name. Kirkbride transferred the three species of Lindenia to Augusta, and separated them based on flower form and geographic range into two subgenera and two sections, based in large part on the work of Darwin (1976). Darwin (1976) studied the three species that have comprised Lindenia, and Delprete (1997) studied the taxonomy and ecology of the Brazilian plants of Augusta.

Augusta was found to belong to Ixoroideae by Bremer & Eriksson (2009), who did not include it in a tribe, however. In a subsequent molecular analysis of the subfamily Ixoroideae, Kainulainen et al. (2013) found the three species of Augusta they studied to be grouped together and a sister group to Wendlandia of Asia; they separated these two genera in the tribe Augusteae.

The taxonomy and taxonomic history of these four species is rather complex for Rubiaceae, probably because the plants are common, showy, and variable morphologically. Several invalid, mis-spelled, or misapplied names have been somewhat commonly used for some of these plants: Siphonia Benth., Ucriana Spreng., Schreibersia Pohl, Bonifacia Manso ex Steud., and Augustea DC. Kuntze added to the confusion by accepting the name Augusta Leandro, which belongs to Asteraceae; Augusta Leandro does have priority over Augusta Pohl, but Pohl's name has been conserved over Leandro's. The two Pacific species of Augusta are quite similar and separated by range but otherwise by rather minor morphological characters; in contrast, several infraspecific taxa were separated by similar or more distinct characters for each of the two continental species by Darwin (1976) and Delprete (1997). Many species with nocturally pollinated flowers are thought to have notable variation in corolla size within the same species, and all the species of Augusta seem to show this.

Augusta is generally similar to and sometimes confused with Rosenbergiodendron, which has similar corollas to the white-flowered Augusta species and somewhat small leaves and lives in seasonal vegetation, but Rosenbrgiodendron differs in its fleshy baccate fruits and leaves often borne on short-shoots.

Author: C.M. Taylor
The content of this web page was last revised on 18 May 2020.
Taylor web page: http://www.mobot.org/MOBOT/Research/curators/taylor.shtml

• Kirkbride, Jr., J. H. 1997. Manipulus Rubiacearum — VI. Brittonia 49(3): 354–379.
• Kainulainen, K., S. G. Razafimandimbison & B. Bremer. 2013. Phylogenetic relationships and new tribal delimitations in subfamily Ixoroideae (Rubiaceae). Bot. J. Linn. Soc. 173: 387–406.
• Delprete, P. G. 1997. Revision and typification of Brazilian Augusta (Rubiaceae, Rondeletieae), with ecological observations on the riverine vegetation of the cerrado and Atlantic forests. Brittonia 49(4): 487–497.
• Darwin, S. P. 1976. The genus Lindenia (Rubiaceae). J. Arnold Arbor. 57(4): 426–449.