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Published In: Florae Columbiae 1: 9, t. 5. 1858. (1859) (Fl. Columb.) Name publication detailView in BotanicusView in Biodiversity Heritage Library
 

Project Name Data (Last Modified On 4/30/2015)
Acceptance : Accepted
Note : Belongs to Tribe Cinchoneae
Project Data     (Last Modified On 9/15/2020)
Notes:

Joosia is a Neotropical genus of at least 18 species shrubs and small trees found in wet forest vegetation from southern Central America through the Andes and their foothills to Bolivia. It is classified in the Tribe Cinchoneae, and is characterized by a lack of raphide crystals in the tissues; a woody habit; opposite leaves with lineolate higher-order venation and without domatia; interpetiolar, ligulate, often obtuse to rounded, deciduous stipules that are held flat together and erect in bud; subsessile to usually pedunculate inflorescences terminal or frequently displaced to pseudaxillary with reduced bracts and usually monochasial, markedly helicoid axes; 4-merous or less often 5-merous, distylous, medium-sized, sessile to shortly pedicellate, fragrant flowers; generally well developed calyx limbs that are lobed or rarely (Joosia dichotoma) spathaceous and splitting into 1 or 2 segments; salverform, white to pale green or pink, externally strigose corollas with the lobes valvate in bud and usually appendaged along the margins; and cylindrical, stiff to woody, septicidal capsules with numerous small, flattened, winged seeds. Many species also have notably well developed pubescence, variously hirtellous, silky-strigose, and/or arachnoid. Steyermark (1975) separated some species of Joosia based on the position of the anthers, near the base of the corolla or higher up, but Andersson (1997) clarified that Joosia species are distylous and the anther position varies between short-styled and long-styled flowers within a single species. In several Joosia species the old capsules valves become characteristically twisted as they dry out after dehiscence. The calyx limb generally disintegrates as the fruits develop, so its form can be difficult to determine on mature fruits. The spathaceous calyx of Joosia dichotoma is fused in bud then splits as the enlarging corolla pushes through it; on some flowers with symmetrically lobed calyx limbs with well developed tubes, the tube may also split as the corolla enlarges but the limb is open in bud with regular lobes (e.g., Joosia pulcherrima). The center of species diversity is in the Andes of Ecuador and Peru. Joosia umbellifera is the most commonly collected species, and is found throughout the range of the genus; also commonly collected is Joosia dielsiana. At least some species have some antimalarial properties and are locally used for this (e.g., Schunke-Vigo 1100).

As noted by Andersson (1997), within species of Joosia as they are currently circumscribed there is often notable variation in density and distribution of pubescence, leaf size (both among plants and on stems of individual plants), calyx limb length and degree of lobing, and capsule size; there is more variation in some of these features within some Joosia species than average in Rubiaceae species. Within the genus there is notable variation among the species in particular in the form of the calyx limb (Andersson, 1997: fig. 1), from shallowly to deeply lobed, short to quite well developed, and regularly lobed to spathaceous (i.e., fused in bud and opening via a longitudinal slit). Steyermark 1975 recognized two subgenera, Joosia subg. Joosia with all the species with a regularly lobed calyx limb, and Joosia subg. Sectocalyx Steyerm., diagnosed by a spathaceous calyx and including only Joosia dichotoma. Andersson (1997) presented a cladistic analysis based on morphological characters that found Joosia dichotoma (called "spathacea" in his fig. 2) nested within Joosia, and therefore Andersson did not recognize Joosia subg. Sectocalyx. Andersson (1997) and Steyermark (1975) differed on the identity of the type of Joosia dichotoma; Andersson (1996) preserved Steyermark's usage through conservation of the material studied by Steyermark as the type of this name. Andersson recognized 11 species of Joosia, with Joosia umbellifera widespread and morphologically somewhat variable, and which included plants that Steyermark separated in two species.

In general aspect and the salverform corollas with elaborately appendaged lobes Joosia is similar to Arachnothryx, which is sympatric, but Arachnothryx differs in its acute and often twisted stipules, reticulated leaf venation, imbricated corolla lobes, and subglobose small capsules with angled seeds, also some Andean species of Arachnothryx do not have appendaged corolla lobes. Joosia is also similar to Guettarda, in particular to several species with inflorescences with 2-4 monochasial axes and appendaged corolla lobes; however Guettarda has acute stipules that are twisted in bud, leaves with the higher-order venation regularly areolate, corolla lobes imbricate in bud, and fleshy drupaceous fruits. Joosia is also similar in general aspect to Macrocnemum and some species of Cinchona, but those have irregularly areolate higher-order leaf venation.

Author: C.M. Taylor
The content of this web page was last revised on 15 September 2020.
Taylor web page: http://www.mobot.org/MOBOT/Research/curators/taylor.shtml

Distribution: Wet forest vegetation at sea level to ca. 3000 m, Costa Rica through Colombia and adjacent western Venezuela to Bolivia. All the Joosia plants known from Venezuela were collected on a sigle sandstone formation in the Cordillera Oriental of the Andes near the Colombian border, and do not seem to match Joosia umbellifera but have not yet been identified to species.
References:

 

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Shrubs and small trees, unarmed, terrestrial, without raphides in ther tissues, sometimes resinous, sometimes with arachnoid pubescence. Leaves opposite, subsessile to petiolate, entire, usually with sericeous or arachnoid pubescence, wiith tertiary and quaternary venation lineolate, sometimes with domatia; stipules interpetiolar, ligulate to ovate, generally held erect and flatly pressed together in bud, deciduous. Inflorescences terminal sometimes displaced to pseudoaxillary, fasciculate to cymose with axes often monochasial, 1--multiflowered, subsessile to pedunculate, bracteate or bracts reduced. Flowers subsessile, bisexual, distylous, protandrous, medium to large, at least sometimes fragrant, diurnal or perhaps noctural; hypanthium elipsoid to cylindrical; calyx limb developed, truncate to spathaceous or 4--5-lobed, without calycophylls; corolla salverform, white to pink or  red, externally often sericeous, internally glabrous, lobes 4--5, triangular, valvate in bud, on tip and sometimes margins with lobulate, petaloid appendages or infrequently wings; stamens 4--5, inserted in corolla tube, anthers narrowly oblong, dorsifixed near base, opening by longitudinal slits, included or partially exserted, without appendages; ovary 2-locular, ovules numerous in each locule, imbricated and ascending on axile placentas, stigmas 2, linear, included. Fruit capsular, cylindrical, septicidally dehiscent from apex, chartaceous to woody, smooth, with calyx limb persistent or tardily deciduous, with valves 2(4), often pesistent and twisted; seeds numerous, flattened, small, fusiform, marginally winged and entire, obtuse to acute at ends.

 
 
 
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