Trichanthera corymbosa Leonard, J. Wash. Acad. Sci.

Daniel, Thomas F., 2015, Synopsis of Trichanthera (Acanthaceae: Ruellieae: Trichantherinae), Proceedings of the California Academy of Sciences 62 (1), pp. 1-23 : 6-8

1. Trichanthera corymbosa Leonard, J. Wash. Acad. Sci. 20:487. 1930.

TYPE.— COLOMBIA. Norte de Santander: Culagá Valley, near Tapatá (N of Toledo ), 1500–2100 m, 3–8 March 1927, E. Killip & A. Smith 20140 (holotype: US!; isotypes: BM!, GH-image!, NY!). Figure 2 .

Trees to 20 m tall; young stems covered with sessile and lenticular glands to 0.05 mm in diameter (often inconspicuous; punctate-glandular) and puberulent with antrorse eglandular trichomes to 0.1 mm long, nodes sometimes with longer flexuose eglandular trichomes as well. Leaves petiolate, petioles to 45 mm long, blades ovate to elliptic to broadly elliptic, 33–265 mm long, 16–140 mm wide, 1.3–2.4 × longer than wide, rounded to cuneate at base, acute to acuminate at apex, surfaces punctate-glandular and sometimes with eglandular trichomes along major veins on abaxial surface, margin sinuate to sinuate-crenate. Inflorescence a terminal corymbose thyrse (or if basally branched, then a panicle of thyrses) 48–149 mm long, rachis punctate-glandular and pubescent with antrorse eglandular trichomes 0.05–0.2 mm long, dichasia expanded to a greater or lesser degree, pedunculate, peduncles to 55 mm long, pubescent like rachis, secondary peduncles similar to peduncles. Bracts often caducous, subfoliose and reduced in size distally, ovate to elliptic to oblanceolate to linear, 7–72 (–170) mm long, 2–34 (–80) mm wide, pubescent like leaves (proximal bracts) or rachis (distal bracts). Bracteoles and secondary bracteoles (subfoliose to) oblanceolate to linear, 4–12 (–25) mm long, 1–3.2 (–5) mm wide. Flowers pedicellate, pedicels 4–11 mm long. Calyx green with purplish tinge, 14–24 mm long during anthesis, tube 2–4 mm long, lobes heteromorphic (4 + 1), four similar lobes linear to linear-lanceolate to linear-elliptic, 8–19 mm long, 2–4 mm wide, acute at apex, fifth (posterior) lobe lanceolate to elliptic to oblong to obovate-elliptic, 12–27 mm long 4.5–8.5 mm wide, longer than and ca. 1.5 or more × wider than other lobes, rounded to acute to attenuate at apex, lobes with abaxial surface punctate-glandular and with eglandular trichomes like those of rachis, margin ciliate with similar eglandular trichomes. Corolla whitish to maroon or purplish (see discussion), (18–) 23–43 mm long, externally punctate-glandular and densely pubescent with retrorsely appressed eglandular trichomes to 0.5 mm long (except for proximal portion of tube which lacks eglandular trichomes), narrow proximal portion of tube 7–15 mm long, throat 8–18 mm long, 9–13 mm in diameter near midpoint, limb 18–34 mm in diameter, lobes oblong to broadly ovate to triangular, 6–12 mm long. Stamens ca. 20–27 mm long, filaments pubescent proximally with flexuose eglandular trichomes to 3 mm long and sometimes with glandular trichomes as well, sometimes glabrous or nearly so distally, thecae 4–6.5 mm long, (glabrous or) pubescent with flexuose eglandular trichomes to 1.5 mm long and on dorsal surface and connective also pubescent with sessile glands (≤ 0.05 mm diam.), pollen (Romero-Castañeda 10753) 72–74 µm (polar axis) × 55–60 µm (equatorial axis, apertural face) × 56–62 µm (equatorial axis interapertural face). Style 28–38 mm long, pubescent proximally, glabrous distally, stigma with 1 lobe straight, 1.5–4 mm long, other lobe vestigial, 0.05–0.2 mm long. Capsule 16–21 mm long, densely pubescent with straight to flexuose eglandular trichomes to 1 mm long. Seeds 3.6–4 mm long, 2.9–3.6 mm wide.

PHENOLOGY.— Flowering: October–March. Fruiting: October–March.

DISTRIBUTION AND HABITATS.— Northern South America (northeastern Colombia and northwestern Venezuela; Fig. 3 ). Plants occur along streams in moist to wet lowland to montane primary and secondary forests (including cloud forests) at elevations from 900 to 1800 m (possibly up to 2300 m fide Bono 1996). The distribution of this species occurs exclusively within that of the more widespread T. gigantea . Indeed, the two species of Trichanthera would appear to be sympatric or at least to grow in the near vicinity of one another; the type of T. corymbosa and a collection of T. gigantea were both collected at the same locality by Killip and Smith in the department of Norte de Santander, Colombia.

LOCAL NAME.— Yátago ( Venezuela; Bono 1996).

USES.— Planted as living fences along roads and streams in Venezuela ( Bono 1996).

CONSERVATION.— Trichanthera corymbosa is known from fewer than 20 collections in a limited geographic region (extent of occurrence = ca. 114,900 km 2; area of occupancy with grid cell area of 4 sq. km = 44 km 2; north-south linear distance = ca. 390 km; east-west linear distance = ca. 560 km). Based on the AOO, the species could be considered as endangered (EN) if two subcriteria under criterion B are met. Three geographically isolated subpopulations could be recognized, all of which are potentially threatened by deforestation; thus, a single location for this species is currently proposed. Based on satellite imagery (e.g., Google Inc. 2013), local deforestation is evident for at least five of the 11 mapped collection sites for this species. Thus two of the three subcriteria needed to make an assessment in a threatened category for this species are fulfilled, and a status of EN (B2, a, b) is provisionally proposed for this species.

MORPHOLOGICAL VARIATION.— Corollas of T. corymbosa are sometimes described as white, whitish, yellow, or flesh-colored. Some of these descriptions possibly refer to the dense covering of whitish trichomes on the external surface. The internal surface is described as white (e.g., Bunting et al. 12260), maroon (e.g., Ruiz T. & López F. 1385), or purple (e.g., Pittier 12828). Thus, as in T. gigantea (see below), there appears to be variation in the color of corollas of this species.

As is evident from the description above there is also variation in the pubescence of the androecium in this species. The thecae of Romero C. 7504 are glabrous whereas they are pubescent (where seen) among other collections. In Romero C. 10753 the portion of the filaments that is exserted from the corolla tube is glabrous; in Trujillo & Fernández 16379, that portion is pubescent with both eglandular and glandular trichomes proximally and glabrous distally. Additional observations on entire androecia in flowers of this species are desirable; based on these observations, however, variation in androecial pubescence of T. corymbosa appears similar to that in T. gigantea .

Inflorescences of T. corymbosa are almost always corymbose; however, in Trujillo & Fernández 16379 from Venezuela they are elongate (up to 230 mm), like those of T. gigantea . Calyx lobes and bracteoles of this collection are like those typical of T. corymbosa , in which species this collection is treated here. Overall length of the inflorescence (measured from the first lateral branch bearing dichasia or, if such is absent, then from first dichasium to the apex of the inflorescence, excluding corollas), although often shorter in T. corymbosa than in T. gigantea , overlaps to an extent that it does not appear to be distinctive for either species. Bunting et al. 12260 is somewhat unusual by its exceptionally large foliose bracts (to 170 × 80 mm) at the base of the inflorescence and its large bracteoles (to 25 × 5 mm) on the proximal dichasia.

A Colombian collection (Cañas 810) shows intermediacy between T. gigantea and T. corymbosa in calyx length (to 15 mm) and form (lobes slightly heteromorphic with the smaller lobes rounded to acute apically). Bracteoles of this collection are like those of T. gigantea , however, in which species this collection is treated. Another collection from Colombia (Norte de Santander: Ocaña, 6000 ft., Kalbreyer 1264 at K) shows intermediacy between the two species in most of the characters noted in the key. Given the apparent sympatry of these species as noted above, similarity of their flowers, and relative ease of artificial interspecific hybridization demonstrated in several genera of Acanthaceae (e.g., Long 1975 and Daniel 2007 for Ruellia L.; Daniel 1983 for Carlowrightia A. Gray ; Daniel 1984 for Anisacanthus Nees ; Daniel 1986 for Tetramerium Nees ), hybridization between the two species of Trichanthera might account for the rare instances of intermediacy observed.

ADDITIONAL SPECIMENS EXAMINED.— COLOMBIA: Cesar: Sierra de Perijá, eastern Manaure, hoya del Río Manaure , San Antonio , J. Cuatrecasas & R. Romero-Castañeda 25341 ( F, US); Cordillera Oriental, Corregimiento Manaure, Finca Los Venados , R . Romero-Castañeda 7504 ( MO, US) . Magdalena: de San Pedro a Cebolleta , R . Romero-Castañeda 10753 ( F, MO, NY) . Norte de Santander: environs de Ocaña, L . Schlim 135 ( BM, K, P) .— VENEZUELA: Mérida: vicinity of Tovar, along Río Mocoties , H. Pittier 12828 ( G, NY, US) . Táchira: Distr. Junín, Las Lajas, entre Delicias y Villa Páez , L. Ruiz T. & M. López F. 1385 (US) . Yaracuy: Distr. Bruzual, Mpio. Campoelías, vertiente sur, próxima a carretera Campoelías – La Laguna – Tupe , B. Trujillo 16021 ( MO); Distr. Bruzual, Mpio. Campoelías, La Puente, riachuelo permanente en carretera Campoelías–Tierrita Blanca , km 10, B. Trujillo & A. Fernández 16379 ( MO, US) . Zulia: Distr. Mara, alrededores de Puesto “ El Bosque” de la Guardia Nacional, 10°47′N, 072°40′W, G. Bunting et al. 12260 ( NY, US); Ayapa [Ayapaina], Sierra Perijá, W of Machiques, Bro. Ginés 147 ( US); Sierra de Perijá , a lo largo de la quebrada del Río Omira –Kuná (Tumuriasa), cerca de la frontera Colombo-Venezolana, SW de Pishikakao e Iría, J. Steyermark et al. 105547 ( G, MO, US) .

Figures

FIGURE 2. Trichanthera corymbosa (A–C) and T. gigantea (D, E).A. Corymbose inflorescence (Romero C. 10753, MO). B. Flower showing calyx with heteromorphic lobes (Pittier 12828, NY). C. Seed (Trujillo & Fernández 16379, US). D. Inflorescence and flower (Daniel et al. 5474). E. Base of tree with suckering (Daniel et al. 5474).

FIGURE 3. Distribution of Trichanthera corymbosa.