The Neotropical Tribe Cinchoneae includes eight or nine genera and about 127 species of shrubs and trees found in wet vegetation from southern Central America to Bolivia and Brazil. It is characterized by by a lack of raphide crystals in the tissues; a woody habit; opposite or whorled leaves; interpetiolar, ligulate, often obtuse to rounded, deciduous stipules that are held flat together and erect in bud; terminal or axillary, cymose to thyrsiform inflorescences with reduced to well developed bracts; 4- or 5-merous, fragrant, usually distylous flowers without calycophylls; corollas small to usually well developed, with the lobes valvate in bud; and cylindrical, stiff to woody, septicidal capsules with numerous small, flattened, winged seeds. The center of genus and species diversity is in the Andes, and Remijia also has a center of species diversity in the northeastern Amazon basin and the Guyana Highlands. In particular Cinchona and Ladenbergia have centers of species diversity in montane forests in the Andes where Remijia is not represented (or so far not known), while Remijia has a center of species diversity in montane areas of the Guayana Highlands where Cinchona is not found and Ladenbergia is represented by only a few species. Several genera of the Cinchoneae are not well known, in particular Maguireocharis has apparently not been recollected since the 1960's, and Stilpnophyllum is not commonly encountered.

The Tribe Cinchoneae was circumscribed quite broadly until Andersson's studies of the group in the 1990's. Prior to this most authors, in particular Standley (various Neotropical floras) and Robbrecht (1988), generally followed Schumann's (1891) classification and included in Cinchoneae most or all of the Rubiaceae with dry capsular fruits with numerous winged, vertically oriented seeds. In this circumscription Cinchoneae had a pantropical distribution and included three to four dozen genera with notable morphological variation. Andersson & Persson (1991) studied this assemblage with morphological characters and cladistic methods, and separated these genera into several tribes and restricted Cinchoneae to thirteen Neotropical genera plus perhaps the Pacific genus Dolicholobium A. Gray. Based on these conclusions Andersson (1995) studied the closely related tribes Cinchoneae, Hillieae, and Calycophylleae in more detail, with more morphological characters, and narrowed the circumscription of Cinchoneae to include eight Neotropical genera, one of them newly described, and provisionally excluded Dolicholobium from the tribe. Here Andersson also synonymized Cephalodendron with Remijia and clarified the separation of Cinchona and Ladenbergia, which had been problematic for a long time. Cinchona and Ladenbergia were traditionally separated based on acropetal vs. basipetal capsule dehiscence, respectively, but Andersson showed that acropetal dehiscence is not consistent in nor restricted to Cinchona, and he separated these genera instead by corolla characters.

Later Andersson & Antonelli (2005) studied Cinchoneae with molecular data and included seven genera, one newly described; they were not able to sample two then-poorly known genera, Pimentelia and Maguireocharis. Subsequently Manns & Bremer (2010) studied the subfamily Cinchonoideae and found further support for Andersson's circumscription of this tribe. Andersson (1994) and Taylor et al. (2004) provided morphological descriptions of several of the genera of the tribe.

The Rubiaceae Tribe Cinchoneae has world importance because it includes Cinchona and several related genera that produce quinine and quinoline alkaloids, which provided the first remedy against malaria and thus allowed colonization and development of much of the tropical world; the search for these medicines also stimulated the fields of taxonomic botany and synthetic chemistry. A podcast on Cinchona and its significance is available in the Encyclopedia of Life's One Species At A Time project. Active study of Tribe Cinchoneae is ongoing, including taxonomic study of various genera and the multidisciplinary international project The Quest for Cinchona - A Phylogenetic Tale that addresses the biogeography, alkaloid chemistry, and conservation of the plants. Several species of Cinchona produce useful quantities of the medicinal alkaloids in their bark, but not all species do this; there is extensive confusion in folk medicine and some ongoing conservation projects over the correct identification of these particular species. A number of Cinchona species are now rare in their native ranges due to exploitation for bark and lumber and habitat destruction, and several are considered threatened with regard to their survival.

Author: C.M. Taylor
The content of this web page was last revised on 29 November 2016.
Taylor web page: http://www.mobot.org/MOBOT/Research/curators/taylor.shtml

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