Sobralia rinconiana Serracín, Samudio & Bogarín, 2022

Serracín, Zuleika, Samudio, Zabdy & Bogarín, Diego, 2022, A new Sobralia (Orchidaceae: Sobralieae) from Panama, Phytotaxa 559 (1), pp. 81-87 : 83-86

Sobralia rinconiana Serracín, Samudio & Bogarín , sp. nov. ( Figures 2 –3 )

Type:— PANAMA. Chiriquí-Bocas del Toro : Bosque Protector Palo Seco, 8°47’30.4”N 82°12’29.8”W, 1141 m, bosque pluvial premontano, terrestres en bosque secundario a orillas del camino, 3 agosto 2014, Z. Serracín, R. Rincón & D. Bogarín 831 (holotype: UCH!, isotype: PMA!) .

Among the Sobralia species, S. rinconiana is characterized by the combination of a large plant size that reaches up to 120 cm high with the chartaceous, larger, and wider leaves (27–35 × 14–16 cm), elliptical-lanceolate, acute to acuminate. Among the species of the genus, S. rinconiana is most similar to S. carazoi but differs (apart from its larger size of plants and leaves), in its grayish, papyraceous sheaths (rather than warty and dark) erect conical, acicular, papyraceous flower bracts without spots (instead of erect, narrow, acute, strongly lepidote), the spreading flowers with reflexed petals and the infundibuliform, cream-yellow lip (vs. campanulate, white flowers with an opened lip of S. carazoi ) in its grayish, papyraceous sheaths, erect conical, acicular, papyraceous flower bracts without spots, the longer and wider sepals 4.0–4.4 × 0.8–1.0 cm (vs. 2.0 × 0.8 cm) and petals 4.2 × 0.9 cm (vs. 1.70 × 0.45 cm), the cream-yellow lip 3.8 × 2.8 cm (vs. white, 1.3 × 1.6 cm), and the longer, suberect column 2.5 cm long (vs. 1.2 cm).

Description:—Erect, terrestrial, large herb 120 cm tall. Roots coarse, fleshy, finely pubescent, 3–5 mm in diameter, and 5-10 cm long. Stem cylindric, round in section, simple, fleshy, erect; up to 85 cm long, 4–5 mm in diameter; bracts, tubular papyraceous, not lepidote, foliate in the upper third, covered by adpressed, green, sparsely subscarious sheaths, becoming papyraceous with age. Leaves plicate, sessile, on a clasping vaginate base, chartaceous, ellipticlanceolate, acute, 3–5 per stem, 27–35 × 14–16 cm, with 9 –11 veins; the uppermost leaf smaller, petiolate, subtending the inflorescence, 7.5–9.0 × 4–5 cm. Inflorescence terminal, developed from a conical cluster of imbricating bracts, successively several-flowered, with a single flower, opened at once, floral bracts acuminate, papyraceous, 1.5–2.0 cm. Floral bracts conical, 2 cm long, acicular, papyraceous. Flowers ephemeral, white, with a cream-yellow lip throat, the lip base reddish tinged, the apex white, membranaceous, to 8.2 cm in diameter. Dorsal sepal elliptic-lanceolate, suberect, conduplicate, dorsally unicarinate, mucronate, entire, 4.0–4.4 × 0.8–1.0 cm. Lateral sepals elliptic to oblong, spreading, conduplicate, dorsally unicarinate, mucronate, entire, 4.0–4.2 × 0.8–0.9 cm. Petals white, ellipticlanceolate, reflexed, spreading, acute, 4.2 × 0.9 cm. Lip infundibuliform, obscurely 3-lobed, oblong, retuse, erect, the base encircling the column, the distal margins spreading, crispate, 3.8 × 2.8 cm, the base of the lamina with two divergent calli. Column hemiterete-subclavate, slightly arched, 2.5 × 0.4 cm, the apex with two acute arms, with two prominent keels at the middle. Anther and stigma ventral. Anther cap cucullate, translucent, rounded, 2-celled, 2 mm in diameter. Pollinia 4, soft, mealy, in two symmetrical pairs of different size, not sharply distinct from the caudicles, each hemipollinarium 1 × 2 mm.

Distribution and Ecology:—Only known from Bosque Protector de Palo Seco, Fortuna along the Cordillera de Talamanca in western Panama. It grows as terrestrial on the roadside secondary forest at 1141 m of elevation ( Figure 4 ). Plants were recorded in flower in August.

Etymology:—Dedicated to Prof. Rafael Rincón, Director of the Herbarium UCH of Universidad Autónoma de Chiriquí (UNACHI), Panama, in recognition of his contributions to the flora of Panama and who encouraged us to study this Sobralia .

Conservation status:— It has not been formally assessed, however, it should be considered data deficient (DD) because more data on population and distribution is needed for a proper assessment.

Taxonomic Discussion:—the most conspicuous characteristic of S. rinconiana is the plant size that reaches up to 120 cm high and its large elliptical-lanceolate, chartaceous, acute to acuminate leaves 30–35 × 14–16 cm. Sobralia rinconiana is similar to S. carazoi C.H.Lankester & Ames (1924: 34) but vegetatively differs (apart from its larger size of plants and leaves) in its grayish, papyraceous sheaths (rather than warty and dark) erect conical, acicular, papyraceous flower bracts without spots (instead of erect, narrow, acute, strongly lepidote), the longer and wider sepals 4.0–4.4 × 0.8–1.0 cm (vs. 2.0 × 0.8 cm) and petals 4.2 × 0.9 cm (vs. 1.70 × 0.45 cm), the cream-yellow lip 3.8 × 2.8 cm (vs. white, 1.3 × 1.6 cm), and the longer, suberect column 2.5 cm long (vs. 1.2 cm). The habit of S. rinconiana is similar to other species such as S. chrysostoma Dressler , S. leucoxantha Reichenbach.f. (1866: 86) , S. undatocarinata C.Schweinfurth (1938: 197) , S. violacea Linden ex Lindley (1846: 133) , and S. warszewiczii Reichenbach (1852: 714) characterized by stems over 100 cm tall, with conspicuous floral bracts forming an imbricating cone; however, the leaf of the new species is larger than the rest of the Sobralia currently registered in Panama. The leaf size of the species similar in plant habit to S. rinconiana is up to 23 cm long and 8 cm wide, contrasting with the leaf of S. rinconiana , which is greater than 30 long and 14 cm wide.

Two peculiar characteristics of S. rinconiana are the small flower size in proportion to the plant height and leaf width. These two morphological features are present at least in S. carazoi , S. doremiliae Dressler (1995: 142) , and S. valida Rolfe (1909: 65) . However, the new species shows spreading flowers with reflexed petals from the middle to the apex. In addition, the infundibuliform, cream-yellow lip contrasts to the campanulate, white flowers with an opened lip of S. carazoi and S. doremiliae . Another similar species, Sobralia valida , shows smaller and narrower leaves (12–20 × 6.0– 8.5 cm) and the lip with crested veins and a yellow band becoming deep orange in front (Rolfe 1909). These characters contrast to the two basal keels not extending along the cream-yellow lip of S. rinconiana .

Figures

FIGURE 2. Sobralia rinconiana Serracín, Samudio & Bogarín: A. habit, B. flower, C. dissected perianth, D. column and section of the lip, lateral view, E. column, ventral and ¾ lateral views, F. anther cap and pollinarium (LCDP from the plant that served as the holotype) by the authors.

FIGURE 3. A-B. Morphology of two flowers of the plant that served as the holotype. Pictures by D. Bogarín.

FIGURE 4. Right and left, study site and natural habitat of S. rinconiana along Bosque Protector Palo Seco, Panama. Pictures by D. Bogarín.