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Published In: Botanical Journal of the Linnean Society 187: 384–385. 2018. (Bot. J. Linn. Soc.) Name publication detail
 

Project Name Data (Last Modified On 3/30/2021)
Acceptance : Accepted
Note : Tribe Chiococceae
Project Data     (Last Modified On 9/15/2021)
Notes :

Adolphoduckea incldes one species of large trees found in wet Amazonian forest. It is characterized by its large size (to 25 m tall); medium-sized leaves with regularly developed pubescent domatia; persistent tubular stipules that tardily split into two segments; terminal cymose inflorescences; notably large and showy flowers with long-exserted anthers and stigmas; very slender white corollas 10-11 cm long with the 6 narrow lobes almost as long as the tube and narrowly imbricated in bud; ellipsoid, strongly flattened, septicidal, medium-sized (3.5 x 2.5 cm) capsules, and medium-sized winged seeds (15 x 7 mm). The stipules are fused around the stem with triangular portions on each interpetiolar side. The leaf domatia often have distinctive crisped, lanulose trichomes that cover a relatively large area of the lamina and along the midrib; similar trichomes are found in related genera.The inflorescence bracts are stipuliform, with usually a tubular form that has rudimentary structures in the place of the leaves on actual stipules; these resemble the calyculus of some other Rubiaceae (e.g., Coffea), but are less regularly developed than in those genera. The corolla lobes are recuved at anthesis, and often fully curled under on dried specimens.The anthers are quite long, ca. 3 cm, on slender flexuous filaments. The capsules are woody and lenticellate, and resemble those of Coutarea hexandra 

Little is known about the biology of Adolphoduckea. The flowers appear to be nocturnal, and the capsules are almost never collected. Paudyal et al. (2018) noted that the corollas turn pink when old. The vegetative stem apices usually have a notable amount of exudate, of unknown composition but shiny similarly to resins found in other Rubiaceae (and confirmed as such). A number of the specimens of Adolphoduckea dried with a blackened color and disarticulated leaves and flowers, which may be an artifact of collecting but this discoloration and disarticulation are more common in specimens of this genus than average for Rubiaceae in the region.  

The single species of Adolphoduckea was long incuded in Exostema, due to its reproductive characters that agreed with that genus as it was variously circumscribed until recently. McDowell & Bremer. (1998:229-230) studied this species in some detail, and noted that it was erroneously described and previously classified as having 5-merous flowers but these are actually 6-merous. They also noted that the characters on which its inclusion in Exostema were based were plesiomorphic in the genus and tribe. Their molecular analysis found Adolphoduckea maynense to be basal to their Exostema clade; their analysis only included species of Exostema plus one outgroup, and it retrieved groups found by later workers but did not find their broader relationships in Rubiaceae. In an analysis with fewer Exostema species but more outgroups, McDowell et al. (2003) found Adolphoduckea related to Coutarea rather than the "core" Antillean Exostema species. 

More recently Paudyal et al. (2018) presented a broad analysis of Chiococceae, and found McDowell & Bremer's (1998) three clades with their basal species placed on other, separated clades. Adophoduckea maynense was placed in their analysis on a clade with Coutarea hexandra, which has fruits and seeds of similar form and similarly large and 6-merous flowers with elongated slender anthers, and is sympatric with Adolphoduckea. The species Adolphoduckea maynense was separated as a monotypic genus by Paudyal et al. here based formally on its differences from Solenandra and Motleyothamnus (p. 384-385) and also its differences from Exostema (p. 380) were noted, although their analysis did not find these genera closely related. They did not diagnose or discuss the differences of Adolphoduckea from Coutarea, its well supported sister group in their analysis; at present, the only such distinctions appear to be plant size and corolla shape. Their explicit taxonomic principle for recognition of monotypic genera is (p. 375) that at least one automorphy must distinguish the species from all other species, so it is hoped that what constitutes an apomorphy in their view will be clarified at some point.   

Coutarea and Adolphoduckea appear in the molecular analyses available to be closely related and to form a monophyletic group. Whether they are combined or separated seems to be, to a large extent, a preference for classification empahsizing shared features or differences. These are provisionally separated here based on recent literature, but a possible future discovery of a species with intermediate corolla morphology might be problematic for their separation.

Author: C.M. Taylor
The content of this web page was last revised on 30 March 2021.
Taylor web page: http://www.mobot.org/MOBOT/Research/curators/taylor.shtml

Distribution : Wet forest at 120-1100 m in the western Amazon basin, occasionally collected in both flooded and non-flooded areas but perhaps more frequent in swamps and flooded areas; Bolivia (Beni, Santa Cruz), Brazil (Acre), Ecuador (Napo, Orellana, Sucumbíos, Zamora-Chinchipe), Peru (Amazonas, Cajamarca, Loreto, Madre de Dios, Pasco, San Martín).
References :

 

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Large trees, unarmed, terrestrial, without raphides in the tissues. Leaves opposite, petiolate, entire, with the higher-order venation not lineolate, with pubescent domatia; stipules fused around stem or tardily splitting and interpetiolar, triangular, erect and perhaps imbricated in bud, persistent. Inflorescences terminal and sometimes also in uppermost axils (or inflorescence with follaceous bracts), cymose, several-flowered, pedunculate, bracteate with bracts usually stipuliform. Flowers pedicellate, bisexual, homostylous, protandrous, large, perhaps fragrant and nocturnal; hypanthium ellipsoid and flattened; calyx limb developed, 6-lobed, without calycophylls; corolla slenderly tubular and elongated (10-11 cm), white perhaps becoming pink with age, densely pilosulous inside, lobes 6, linear-ligulate, thinly imbricated (quincuncial) in bud, strongly recurved at anthesis, without appendages; stamens 6, inserted near base of corolla tube, filaments thickened and coherent at base, anthers linear and well developed (3 cm), basifixed, dehiscent by linear slits, exserted, sagittate at base and with apiculate appendage at top; ovary 2-locular, with ovules numerous in each locule, on axile placentas, stigma shortly biblobed, exserted. Fruit capsular, ellipsoid and strongly laterally flattened at 90° to the septum, septicidally dehiscent from apex with valves separating, woody, smooth except lenticellate, with calyx limb deciduous; seeds numerous per locule, flattened, medium-sized (15 x 7 mm), ellipsoid, flattened, marginally with concentric wing, wing entire, papery.

 
 
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