Prosthechea × riopretensis T.L.Vieira & E.L.F.Menezes, 2024

Vieira, Tiago L., Viotti, Julia & Menezes, Euler L. F., 2024, A new nothospecies of Prosthechea (Orchidaceae: Laeliinae) from the Diamantina Plateau, Minas Gerais, Brazil, Phytotaxa 665 (3), pp. 282-290 : 284-287

Prosthechea × riopretensis T.L.Vieira & E.L.F.Menezes , nothosp. nov.

( Figures 3–4 )

Type: — BRAZIL. Minas Gerais: São Gonçalo do Rio Preto , capão na beira do parque, 1549 m a.s.l., 28 July 2023, fl., E.L.F. Menezes 935 (holotype: HDJF [barcode 00010667]; isotypes: BHCB, BHZB, HUEFS) .

A putative natural hybrid between Prosthechea calamaria and P. faresiana combining features of both parents, with shape and dimensions of both vegetative and floral traits reflecting the former, such as short plants (≤ 19 cm height) and inflorescences (≤ 7 cm long), and flowers with small ovate lips (blade ≤ 1 cm long), whereas the color of sepals and petals remarkably match with the latter, where the internal surface of sepals and petals are covered with vinaceous longitudinal stripes, representing a color pattern never seen within the floral variation of P. calamaria .

Description:—Epiphytic herb, rhizomatous, 11–19 cm height. Rhizome conspicuous, 2–2.5 × 0.3–0.4 cm. Roots white, glabrous, flexuous, ca. 2 mm diameter. Pseudobulbs green, heteroblastic, fusiform, smooth, stipitate, the base covered by scarious sheaths, 5.0–6.5 × 0.6–0.8 cm, 2-leaved. Leaves green, subcoriaceous, lanceolate or narrowly oblong, 6.5–12.0 × 1.0– 1.5 cm, acute. Spathe conduplicate, elliptic, 1.0–1.2 × 0.4–0.8 cm, obtuse. Inflorescence erect, 6.0–7.0 cm long, 4–6-flowered; bracts deltoid or triangular, embracing the rachis and pedicel. Flowers non-resupinate, delicate, greenish white to yellowish, covered by vinaceous longitudinal stripes; pedicel + ovary greenish, narrowly oblong, 1.0–1.2 × 0.3–0.4 cm. Sepals greenish white to yellowish, covered by blurry longitudinal vinaceous stripes on internal surface; dorsal sepal lanceolate, 1.2–1.7 × 0.3–0.5 cm, acute or acuminate; lateral sepals oblong-lanceolate, slightly falcate, 1.2–1.7 × 0.3–0.5 cm, acuminate. Petals greenish white to yellowish, covered by blurry longitudinal vinaceous stripes on adaxial internal surface, oblanceolate, 1.0–1.5 × 0.2–0.3 cm, acuminate. Lip entire, clawed, white with vinaceous maculae surrounding the callus, the blade ovate, 0.7–1.0 × 0.4–0.6 cm, shortly acuminate; callus white, elevated, pad-like, pubescent at the base, ca. 4.5 × 2.2 mm. Column greenish at the base becoming whitish towards the apex, with some faint vinaceous dots and stripes on the dorsal side, shortly claviform, gibbous, 0.6–0.7 × 0.3–0.4 cm; stigmatic cavity obcordiform; clinandrium 3-toothed, all teeth acute, the midtooth eventually laciniate, and bearing a fleshy, knob-like, dorsal appendix. Anther yellow, obloid, ca. 1.1 × 0.9 mm; pollinia 4, yellow, discoid, laterally flattened. Capsule not seen in mature state, but green and triquetrous, as typical for the genus, while still on development.

Distribution and ecology: — Prosthechea × riopretensis is known only from the type locality in the surroundings of Rio Preto State Park (Parque Estadual do Rio Preto), municipality of São Gonçalo do Rio Preto, Minas Gerais, Brazil. It was found in a forest patch (capão de mata) associated to campos rupestres formations, at an elevation of ~ 1500 m a.s.l., occurring as epiphyte. Regarding the putative parents, Prosthechea calamaria occurs in the Espinhaço Range inhabiting both forests and campos rupestres formations, with records concentrated in the Serra do Cipó region. Although there are no herbarium records of the species from Rio Preto State Park or surroundings, a field observation at Serra da Bicha, within the Diamantina Plateau at the municipality of Serro, is confirmed by one of the authors (ELFM). Prosthechea faresiana is usually found only on the exposed quarzitic outcrops of the campos rupestres, generally as a litophyte, and seems to be endemic to the Diamantina Plateau region ( Figure 2 ). We could just find one hybridization zone, which corresponds to the forest patch (capão de mata) of the type locality. Unfortunately, there is no available information about pollinators for either the new nothospecies or its putative parents.

Prosthechea × riopretensis was found flowering in situ in July, whereas in cultivation it flowered from April to July with some plants starting to develop fruits in May. Regarding the putative parents, herbarium records of P. calamaria in the Espinhaço Range indicate flowering period ranging from May to September, with fruits in September as well, whereas in P. faresiana the flowering goes from April to October, with no herbarium specimens presenting fruits among the examined material.

Etymology: —The epithet “ riopretensis ” refers to the municipality of the type locality, São Gonçalo do Rio Preto.

Taxonomic discussion: —We are proposing the taxon as a natural hybrid considering its morphological features, matching with two other species of the genus that occur in the region: Prosthechea calamaria and P. faresiana . The shape and dimensions of both vegetative and floral traits of the new nothospecies overlap with the former, whereas its floral color pattern remarkably match with the latter. Noteworthy, this floral color pattern has never been seen in P. calamaria across its distribution. Prosthechea ×riopretensis can be distinguished from P. calamaria by the color of the flowers (sepals and petals covered by vinaceous stripes on the internal surface vs. entirely white or creamish white, eventually vinaceous maculate at the base), and from P. faresiana mostly by plant size (≤ 18 vs. ≥ 20 cm height), pseudobulb diameter (0.6–0.8 vs. 1.8–2.3 cm), leaf width (≤ 1.5 vs. ≥ 2.0 cm), inflorescence length (≤ 7.0 vs. ≥ 12.5 cm), petal width (≤ 3 vs. ≥ 5 mm), and lip’s blade shape and width (ovate, 0.4–0.6 cm width vs. widely obovate or subcircular, 0.8–1.0 cm width). A full comparison of the main vegetative and floral traits in P. × riopretensis and its putative parents is presented on Table 1 .

Additional specimens examined: — Prosthechea calamaria — BRAZIL. Minas Gerais: sine loco acurato, 1934, fl., s. leg. (RB, barcode 00259528); Conceição do Mato Dentro, Parque Natural Municipal do Ribeirão do Campo, 23 April 2003, fl., R.C. Mota et al. 2560 (BHCB); Jaboticatubas, Serra do Cipó, 3 May 2005, fl., A.P.P. Barbero 32 (SP); ibid., 5 July 2006, fl., A.P.P. Barbero 45 (SP); ibid., 5 July 2006, fl., A.P.P. Barbero 44 (SP); ibid., 12 July 1940, fl., M. Foster & R. Foster 619 (AMES); ibid., fl. in cult., July 2018, fl., T.L. Vieira 467 (HUEFS); Santana de Pirapama, Serra do Cipó, acesso pela Faz. Inhame, trilha da senhorinha, 28 February 2009, fl., D.C. Zappi et al. 1672 (RB, SPF); Juiz de Fora, 1879, fl., R.F.H. Wawra 173a (W); Ouro Preto, Campo Grande, s.d., fl., s. leg. (OUPR 8736); Rio Preto, Serra Negra, trilha para o Burro de Ouro, 21 May 2006, fl., A.L. Santiago 3 (CESJ); Santana do Riacho, Serra do Cipó, 10 April 1980, fl., F. de Barros 224 (SP); Serra do Cipó, estrada MG-010 ca. 400 m antes da bifurcação entre o Morro do Pilar e Conceição do Mato Dentro, 22 September 1993, fr., M.T.V.A. Campos & E.D.P. de Souza CFSC13396 (SP, SPF); PARNA Serra do Cipó, próximo à estrada do Juquinha, 13 June 2009, fl., J.E.Q. Faria et al. 543 (UB); Sete Lagoas, Serra do Cipó, s.d., st., s. leg. (RB); Serra do Cipó, 20 June, fl., L. Damazio s.n. (RB).

Figures

FIGURE 2. Map indicating the type locality of Prosthechea ×riopretensis and known distribution of the putative parental species, P. calamaria and P. faresiana, highlighting the Diamantina Plateau region, in Minas Gerais, Brazil.

FIGURE 3. Composite Digital Plate of Prosthechea ×riopretensis. A. Habit. B. Detail of a sympodium bearing an inflorescence. C. Flower, frontal view. D. Flower in ¾ view. E. Detail of the column and lip in front view. F. Floral dissection: F1. Dorsal sepal; F2. Lateral sepals; F3. Petals; F4. Lip. G and H. Lateral view of the pedicel+ovary and column with and without lip attached, respectively. J. Detail of the anther cap. K. Detail of the pollinia. (Designed by JV).

FIGURE 4. Holotype sheet of Prosthechea ×riopretensis. Courtesy of the herbarium HDJF.