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Published In: Histoire des Plantes de la Guiane Françoise 1: 154, pl. 59. 1775. (Jun-Dec 1775) (Hist. Pl. Guiane) Name publication detailView in BotanicusView in Biodiversity Heritage Library
 

Project Name Data (Last Modified On 5/12/2020)
Acceptance : Accepted
Note : Tribe Lasiantheae
Project Data     (Last Modified On 5/15/2020)
Notes:

Ronabea Aubl. includes three neotropical species of low shrubs found in wet forests and gallery forests from Belize to Amazonian Brazil. Ronabea has opposite leaves; raphides in its tissues; narrowly triangular, persistent, interpetiolar stipules; shortly cymose to subcapitate, few-flowered, axillary inflorescences with bracts; sessile, small, distylous flowers; white salverform corollas with five valvate lobes; bilocular ovaries with the basal ovules solitary in each locule; rather small, purple-black, drupaceous fruits; 2 unilocular pyrenes that are smooth on the adaxial surface and open by a preformed ventral lid; and oily endosperm (Taylor, 2004).

In spite of its small number of species, Ronabea has a rather complicated nomenclatural history as summarized by Taylor (2004), due in large part to their broad ranges and morphological variation. The three species are distinctive, and Ronabea emetica is morphologically rather distinct from the other two species. Smedmark et al. (2014) studied Ronabea latifolia and Ronabea emetica, each represented by one sample, and found them placed on a grade rather than forming a monophyletic group. They suggested that Ronabea is not monophyletic on this basis. These species both include a notably large geographic range with significant morphological and ecological variation, and It seems likely that when they are studied in detail, both of these will be found comprise several distinct species with most of them as-yet undescribed (R. Foster, pers. comm.). In particular Ronabea latifolia varies in leaf size, shape, and pubescence, degree of expansion of the inflorescences, and corolla size. Here this species is circumscribed broadly, pending detailed future studies that will need to include field work. Ronabea emetica is similarly variable across its range, including in fruit color.

Before its association with Psychotria, the identity of Ronabea was unclear and it was applied to species of various genera in various tribes.As the systematics of the Rubiaceae became clearer, Ronabea was long considered closely related to or synonymous with Psychotria L., though a few authors have recognized it as a separate genus of Psychotrieae (e.g., Bremekamp 1934). Ronabea species were anomalous in Psychotria in their oily endosperm and also their combination of axillary inflorescences (i.e., borne in both axils at each node), persistent triangular stipules, and blue-black rather than red fruits. Ronabea is now included in the Lasiantheae, based on both morphological and molecular data (Piesschaert et al., 2000; Smedmark et al., 2014), and Smedmark et al. found it most closely related to the African Trichostachys and the Malagasy Saldinia

Author: C.M. Taylor. The content of this web page was last revised on 11 May 2020.
Taylor web page: http://www.mobot.org/MOBOT/Research/curators/taylor.shtml

Distribution:

Neotropics: wet lowland forests and gallery forests, Belize through Central America to the Amazon basin, from Colombia to northern Bolivia, and from the Guianas to eastern Brazil.

References:

 

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Trees, shrubs, or suffrutescent subshrubs, unarmed, terrestrial, with raphides in the tissues. Leaves opposite, petiolate, entire, with higher-order venation not lineolate, without domatia; stipules interpetiolar or shortly fused around the stem, triangular to subulate, generally erect and valvate or perhaps imbricated in bud, persistent. Inflorescences axillary, subcapitate to congested-cymose, few-flowered, sbsessile to pedunculate, bracts developed. Flowers sessile, bisexual, at least usually distylous, protandrous, generally small, whether fragrant unknown, perhaps diurnal; hypanthium ellipsoid to subglobose or turbinate; calyx limb reduced to developed and 5-lobed, without calycophylls; corolla salverform, white, internally glabrous in tube and barbate in throat to pubescent on lobes, lobes 5, triangular, valvate in bud, with appendages; stamens 5, inserted near or above middle of corolla tube, anthers ellipsoid to oblong, dorsifixed near base, opening by linear slits, without appendages, included or exserted; ovary 2-locular, with ovules 1 in each locule, basal; stigmas 2, included or exserted. Fruit drupaceous, subglobose to ellipsoid, juicy, at maturity blue or purple-black, with calyx limb persistent; pyrenes 2, 1-locular, hemispherical (i.e., planoconvex), bony, dehiscent by preformed ventral lid, generally with median furrow adaxially; seeds 1 per pyrene, hemispherical to ellipsoid. 

 

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Key to Species of Ronabea
 
1. Stems and leaves, at least adaxially, pilose to hirsute...R. isanae
1. Stems and leaves glabrous to hirtellous or strigillose.
     2. Leaves 7-15 x 2-6 cm, drying membranaceous to papyraceous; calyx limb lobed for more than 1/2...R. emetica
     2. Leaves 6-20 x 3-10 cm, drying stiffly papyraceous to chartaceous; calyx limb lobed for less than 1/4...R. latifolia
 
 
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