Prosthechea sessiliflora (Edwall) Higgins (1998: 380)

Vieira, Tiago L., Morais, Isa Lucia De & Berg, Cássio Van Den, 2023, Rediscovery of Prosthechea sessiliflora (Orchidaceae, Laeliinae) in the Brazilian Cerrado domain provides valuable taxonomic data and allows nomenclatural adjustments, Phytotaxa 620 (1), pp. 94-100 : 96-99

Prosthechea sessiliflora (Edwall) Higgins (1998: 380) .

≡ Epidendrum sessiliflorum Edwall (1903: 194 , t. 4). ≡ Encyclia sessiliflora (Edwall) Pabst (1967: 277) . ≡ Hormidium sessiliflorum (Edwall) Pabst et al. (1981: 182) . ≡ Anacheilium sessiliflorum (Edwall) Withner & Harding (2004: 115) . ( Figure 2 ).

Type:— BRAZIL. S„o Paulo: [habitat in silvis virgineis ad] Serra Negra, January, G. Edwall s.n. (lost). Lectotype (designated here):— original line drawing reproduced in Edwall (1903: t.4). Epitype (designated here): — BRAZIL. Goiás: Refúgio de Vida Silvestre Serra da Fortaleza , Quirinópolis , fl. in cult., 30 April 2023, I.L. de Morais 8245 (JAR!).

Description:— Epiphytic herb, caespitose, 13.0–20.0 cm tall. Rhizome inconspicuous. Pseudobulbs ovoid to fusiform, 3.5–7.0 × 2.0– 2.5 cm, slightly compressed laterally, (1–)2-leaved. Leaves oblong-elliptic, 11.5–17.0 × 2.0– 2.8 cm, acute. Inflorescence racemose, 3.3–4.0 cm long including flowers, ca. 1.5 cm long peduncle and rachis, 2–5-flowered; spathe ovate, 1.2–1.8 × 0.6–1.2 cm long. Flowers non-resupinate, somewhat fleshy, overall cream to yellowish; pedicel + ovary claviform, triquetrous, ca. 10.0 × 4.0 mm long; dorsal sepal oblong-ovate, 10.0–11.0 × 5.0–7.0 mm, acute, margins entire, laterals sepals ovate, slightly asymmetrical, 10.0–11.0 × 5.0–7.0 mm, acuminate, margins entire; petals elliptic, slightly asymmetrical, ca. 8.0 × 4.0 mm, acute, margins undulate; lip adnate to the column for about half length of the column, inconspicuously 3-lobate in natural position, entire when flattened; free portion elliptic and markedly concave in natural position, with margins elevate from middle to distal portion, ovate when completely flattened, 5.0– 6.8 × 3.5–4.0 mm, obtuse in natural position, rounded when flattened; callus comprising 2 elevated parallel lamellae, extending until the midportion, ca. 2.8 mm long, glabrous. Column 4.0–5.0 × 3.0– 3.5 mm; clinandrium 3-dentate, teeth subequal, the midtooth ligulate, projecting over the anther, bearing a dorsal fleshy rounded appendage; anther not seen; pollinia 4. Capsule ellipsoid, 2.4–3.0 × 1.5–2.0 cm, triquetrous, pendant to subpatent.

Distribution and ecology: —Endemic to Brazil. Although P. sessiliflora was described from the Atlantic Forest domain, in the region of Serra Negra, state of S„o Paulo, it was never recollected again on the domain. Pabst and Dungs (1975) cited the species to the states of S„o Paulo and Minas Gerais, the latter partially within the Cerrado domain. The recent rediscoveries of the species are in the Cerrado domain as well, in the municipalities of Quirinópolis, Goiás, and Chapadad„o do Sul, Mato Grosso do Sul ( Barros et al. 2018, Paiva-Neto & Barros 2021), both sites within the Parnaíba River Basin ( Figure 3 ). The specimens were found in gallery forest vegetation as epiphytes. There is no information about which pollinators are related to the species. Flowering from December to May, fruits in December.

Etymology:—The specific epithet refers to the very short inflorescences.

Nomenclatural notes: — Most of Edwall’s collections from Brazil are related to his work as member of the “Comiss„o Geográfica e Geológica do Estado de S„o Paulo”, whose majority of type materials are currently deposited at SP, with duplicates spread in some European herbaria ( Stafleu & Mennega 2000). Regarding Edwall’s orchid types specifically, they are divided between SP and BR herbaria, since materials were sent to Alfred Cogniaux for the development of his taxonomic treatment of Orchidaceae for the Flora Brasiliensis ( Cogniaux 1893 –1896, 1898–1902, 1904–1906). However, Epidendrum sessiliflorum (= P. sessiliflora ) was described after ( Edwall 1903) the publication of the volume including Epidendrum ( Cogniaux 1898) . Notwithstanding, there are Edwall’s orchid collections from Brazil deposited in BR dating until 1905, what indicates a continuous influx of materials being sent at that period. Later, Cogniaux (1906) included the species in the addenda volume of Orchidaceae , where the type was cited without herbarium indication, what suggests he did not see the material. Unfortunately, there is no sign of P. sessiliflora type material in SP, BR, or any of the herbaria revised by the authors, and its whereabouts remains unknown suggesting that it was likely lost.

Herein, the necessary nomenclatural adjustments are provided, including the lectotypification of the original illustration presented in the protologue, and the indication of the material I.L. de Morais 8245 (JAR) as epitype.

Specimens examined: — BRAZIL. Goiás: Quirinópolis, Refúgio de Vida Silvestre Serra da Fortaleza , fr., 15 December 2021, I.L. de Morais 6870 (JAR); ibid, fl. in cult., 30 April 2023, I.L. de Morais 8245 (JAR) .

Taxonomic discussion: —Although P.sessiliflora has a vegetative morphology typical for the genus, with fusiform pseudobulbs somewhat laterally compressed bearing two oblong-elliptic leaves apically, its floral morphology is quite particular, especially in relation to the Brazilian species of the genus. The lip is concave, but not in a showy way as in other concave lip species such as P. cochleata Linnaeus (1763: 1351) Higgins (1998: 377) or P. fragrans Swartz (1788: 123) Higgins (1998: 377) . It gives the impression of being 3-lobed in natural position, since the margins become elevate only at the distal portion of the lip, turning it into a concave shape, whereas the basal portion of the lip blade is not elevated (see Figure 2G ). However, the outline shape of the lip becomes clearly entire when flattened. Another peculiar aspect of the lip is the callus morphology, consisting of two parallel and elevated lamellae, a morphological character not common in Prosthechea , where the callus is generally an entire and oblong pad-like elevation.

It is interesting to point out that the specimen maintained in cultivation (I.L. de Morais 8245) coming from the material collected in the Refúgio de Vida Silvestre Serra da Fortaleza, presented an abnormal development of its leaves, with only one leaf fully developed. In contrast, the other leaf could not fully develop on the newest and flowering sympodium (see Figure 2A ).

Phylogenetic positioning: —In a recent molecular phylogenetic reconstruction of the genus, Vieira et al. (in press) recovered P. sessiliflora as an early divergent lineage of a clade that also includes two essentially Mesoamerican species, P. cochleata and P. trulla Reichenbach f. (1856: 214) Higgins (1998: 381) , as sisters, which in turn is sister to a clade including P. pygmaea Hooker (1833 : t. 3233) Higgins (1998: 380), P. pseudopygmaea Finet (1889: 121, t.3) Higgins (1998: 380), and P. rhynchophora Richard & Galeotti (1845: 20) Higgins (1998: 380) , whose are also essentially Mesoamerican, except by P. pygmaea that is widespread distributed in the Neotropical region. That would be explained by two potential hypotheses, one considering a long-distance dispersal event of a potential Mesoamerican common ancestor, or another considering a Neotropical widespread common ancestor, with P. sessiliflora representing a species that evolved from relictual populations of this putative widespread common ancestor.

Preliminary conservation assessment: —Based on the known records, P. sessiliflora has estimated EOO and AOO values of 264,264 km 2 and 20 km 2, respectively. However, it is important to mention that three of the five known records represent historical collections that do not have associated vouchers anymore (lost materials), with the most recent of those dating from 1970, without further recollections on those locations. Additionally, the region where the recent rediscoveries were found, the northeast portion of Mato Grosso do Sul and southwest portion of Goiás, are in an expanding agricultural and cattle ranching frontier within the Cerrado domain, where landscape has been dramatically modified, while the original vegetation severely reduced and fragmented ( Strassburg et al. 2017, Renon et al. 2020, Morais et al. 2021, Colli-Silva & Morais 2022, Renon et al. 2023, Soares et al. 2023, Sousa Silva et al. 2023). Just to illustrate the situation of the region, the location where the specimen Paiva-Neto 18 (SP) was recently found in Mato Grosso do Sul (gallery forests within Fazenda Salto do Indaiá, in the municipality of Chapad„o do Sul) was flooded after the installation of a dam (V.B Paiva-Neto pers. comm. 2021) to subsidize agricultural activities. Therefore, we are evaluating and assessing P. sessiliflora as an endangered species (EN) based on criteria B1 (<500 km 2 of AOO), and its conditions ‘a’ (≤ 5 known locations) and ‘b’ [observed and projected continuing decline of EOO (i), AOO (ii), extent of habitat (iii), and number of locations (iv)] of IUCN.

Both recent rediscoveries of the species, Paiva-Neto 18 (SP) and Morais 6870 (JAR), also provided material for cultivation. The former has been maintained in cultivation at Orquidário Frederico Carlos Hoehne of Instituto de Pesquisas Ambientais, in S„o Paulo, whereas the latter specimen at the second author (ILM) private collection in Quirinópolis, Goiás. Efforts for in situ and ex situ conservation of the species should be encouraged, including in vitro germination, cultivation, and propagation.

Figures

FIGURE 2. Composite Digital Plate of Prosthechea sessiliflora (Orchidaceae). A. Habit. B. Detail of the new sympodium and its short inflorescence. C. Sympodium with fruits. D. Flower, frontal view. E. Side view of flower. F. Flora dissection: f1. Dorsal sepal; f2, f3. Lateral sepals; f4, f5. Lateral petals; f6. Lip. G. Lip in detail. H. Ovary and ventral view of column. I. Lateral view of ovary and column with lip. with lip. (Photos taken by ILM and digital plate designed by TLV).

FIGURE 3. Distribution map of Prosthechea sessiliflora (Orchidaceae). The red circles indicate the known records of the species, including historical records without current physical vouchers (lost materials) and the recent rediscoveries in the Cerrado domain.