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Published In: Boletín de la Sociedad Venezolana de Ciencias Naturales 25: 24. 1963. (Bol. Soc. Venez. Ci. Nat.) Name publication detail
 

Project Name Data (Last Modified On 1/10/2013)
Acceptance : Accepted
Project Data     (Last Modified On 1/10/2013)
Notes:

The genus Dioicodendron includes two or perhaps several species of shrubs and trees found mainly in wet montane forests of Venezuela and to northern Bolivia. This genus has not been well known or documented until recently. It can be recognized by its generally robust woody habit; its unusual interpetiolar stipules, which are usually rounded and reflexed; its many-flowered cymose to paniculiform terminal inflorescences; its small, white to pale green, unisexual flowers borne on dioecious plants; its corollas with four lobes that are generally longer than the tube; and its numerous small, ellipsoid to obovate, papery to woody septicidal capsules with tiny angled to subglobose seeds. These plants were originally included in Chimarrhis provisinally, but were separated from that genus by Steyermark (1963) based on the dioecious breeding biology, 4-merous flowers, glabrous filaments, and distinct stipule form. Bremer & Eriksson (2009) included Dioicodendron together with Chimarrhis in the tribe Condamineae; dioecious reproductive biology is rare or perhaps restricted to Dioicodendron within this group. Delprete (1999: pp. 189-190, figs. 82, 83) provided a diagnostic illustration of the characters of the genus, and micrographs of the seeds (p. 41, fig 11A) and pollen (p. 51, fig. 18G-H).

In the protologue, Steyermark (1963) described the corollas of Dioicodendron as 5-lobed, but this is apparently a typographical error because he separated this genus here based on the flowers that are "tetramerous". Steyermark recognized two species, and the range of the genus as only extending to extreme northern Peru. Dioicodendron was revised by Delprete (1999), who recognized one widespread variable species and synonymized several names. Delprete described the corolla lobes in bud as "valvate with contact zone"; these are valvate similarly to other Rubiaceae, and the meaning of this is not entirely clear. Delprete described the stigmas as spreading in the middle parts but remaining coherent or in contact at maturity, but in at least some plants these are spreading maturity. Delprete considered Dioicodendron dioicum to be at significant risk of extinction due to habitat destruction of seasonal forest vegetation in the Andes, but this does not seem to be the case based on our current knowledge of these plants, which includes documentation of a larger range mainly in wet forests. The taxonomy of Dioicodendron here differs from Delprete's work in recognizing more than one species.

Dioicodendron is similar in general vegetative aspect to some plants of Cinchona, which have well dveloped, ascending, rounded stipules, and these genera have been confused in sterile condition. True Chimarrhis can be separated by its bisexual flowers, usually 5-merous flowers, pubescent filaments, and stipules that are characteristically triangular, acute, and tightly convolute in bud.

Author: C.M. Taylor.
The content of this web page was last revised on 3 January 2013.
Taylor web page: http://www.mobot.org/MOBOT/Research/curators/taylor.shtml

 

Distribution: Wet premontane, montane, and cloud forests generally at 1500--3000 m in the northern and central Andes, in Venezuela, Colombia, Ecuador, Peru, and northern Bolivia. The genus is found to as low at ca. 500 m in the extremely wet western slopes of Pacific Colombia. Delprete (1999) reported Dioicodendron as "rare in understory of seasonally dry forest and its remnants, rarely in seasonal cloud forest, also on cleared slopes", but the collections seen are predominantly if not all from forest that is described as very wet. The plants are not commonly collected in any given area, but several of the species are apparently rather uncommon over relatively large ranges.
References:

 

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Large shrubs and small to medium-sized trees, unarmed, terrestrial, without raphids in tissues. Leaves opposite, with tertiary and quaternary venation no lineolate, without domatia; stipules interpetiolar, deciduous, ligulate to ovate, generally obtuse to rounded and spreading to reflexed. Inflorescences terminal on main stem and usually uppermost axillary branches, thyrsiform to paniculiform-cymose, multiflowered, pedunculate, bracteate. Flowers unisexual on dioecious plants, subsessile to pedicellate in groups of 3-7, small, fragrant; hypanthium of pistillate flowers ellipsoid, of staminate flowers reduced to shortly obtriangular; calyx limb 4-lobed, without calycophylls; corolla shortly funnelform to rotate or shortly salverform, white to cream or pale green, internally glabrous, lobes 4, ligulate to ovate, valvate in bud; stamens in staminate flowers 4, inserted in corolla tube, glabrous, anthers ellipsoid, dorsifixed, exserted, the pistillate flowers without staminodes; ovary in pistillate flowers 2-locular, ovules numerous in each locule, horizontal on axile placentas, in staminate flowers reduced; stigmas 2-lobed, rather succulent, exserted, the staminate flowers without pistillodes. Fruit capsular, obovoid to ellipsoid-oblong, woody to chartaceous, septicidally dehiscent frmo apex, valves spreading but remaining fused at base; seeds tiny, angled to suborbicular, foveolate, with short wing around circumference or sometimes on angles.

 

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Key to Species of Dioicodendron; by C.M. Taylor

1. Flowers all pedicellate, pedicels 0.5-3 mm long, generally flexuous; calyx limb 0.2-1 mm long, lobes deltate to narrowly triangular. equal to a little unequal; corolla with tube 0.1-1 mm long, lobes 1-2 mm long, staminate corolla shortly salverform with tube about equal to lobes, pistillate corolla rotate with tube reduced; stigmas 1.5-2 mm long; capsules 2-3.5 x 2-3 mm...Dioicodendron cuatrecasasii

1'. Flowers subsessile to pedicellate, pedicels to 2 mm long, generally ascending; calyx limb 0.5-3 mm long, lobes deltate to linear or ligulate, equal to markedly unequal, sometimes variable in size between different flowers on the same inflorescence; corolla with tube 0.3-1 mm long, lobes 1.5-2.5 mm long, corollas of both flower types rotate or subrotate, with tube much shorter than lobes; stigmas 0.7-1 mm long; capsules 4.5-5 x 2.5-3 mm long...Dioicodendron dioicum

 
 
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