A new record of Dryadella mocoana (Orchidaceae: Pleurothallidinae) from southeastern Ecuador

ABSTRACT Dryadella mocoana which was hitherto thought to be endemic to Mocoa, Putumayo department in Colombia has now been reported for the first time in the lower montane forests of Zamora-Chinchipe province, southern Ecuador. A Lankester composite digital plate (LCDP), photos, taxonomic comments, and an updated description of the species based on the examined material is provided.


Introduction
In 1871 Reichenbach described in Pleurothallis the two first species of the future genus Dryadella: Pleurothallis ariculigera Rchb. f. and Pleurothallis aviceps Rchb. f.; those were subsequently transferred to Masdevallia. Reichenbach later in 1875 described another species of Dryadella as Masdevallia simula Rchb. f. In Woolward ´s monograph of Masdevallia in 1896 Masdevallia obrieniana Rolfe and M. simula were placed in Reichenbach section Saltratices. In 1906 Alfred Cogniaux added five species to the future Dryadella. Kränzlin in 1925 included all species known at that time in section Rhombopetalae, except for Masdevallia lilliputiana which he wrongly placed in his section Floribundae [1]. In 1978, Luer created the genus Dryadella, including species previously placed in Masdevallia and Pleurothallis [2].
Dryadella comprises [3,4] 59 species distributed in the Neotropics from Mexico to southern Brazil [1]. The genus is characterized by the transversely carinate sepals, multi-angled petals and the long-unguiculate lip [1]. In South America, Dryadella species have a disjunction distribution in the Andean and Atlantic regions, except for Dryadella ana-paulae V.P. Castro, B. P. Faria & A. D. Santana, and Dryadella osmariniana (Braga) Garay & Dunst., found at intermediate biomes [5]. In Ecuador, 18 species of Dryadella are currently reported, distributed from 400 to 2000 meters of altitude; of which, Dryadella maryliniana is the most recently described species [8].
In his treatment of Dryadella, Luer [2] described Dryadella mocoana in honour of Mocoa, a community in southern Colombia. The type specimen was collected in the department of Putumayo by J.M. Serna in 1977 [2]. Currently, there appear to be no official records of D. mocoana outside Colombia. In the present work, new specimens were collected during a botanical expedition aimed to register the orchid flora of Zamora Chinchipe province in southeast Ecuador.

Materials and methods
The specimens of the reported species were cultivated at the Vivero de Conservación La Paphinia and the holotype and the examined specimen was deposited at the herbarium of the Universidad Técnica Particular de Loja (HUTPL). The type collection image obtained from SEL was consulted. The taxonomic revision of Dryadella by Luer [1] and the original description from the holotype of the related species [6] were consulted and compared to confirm the identity of the species. Photographs were taken with a Panasonic camera model FZ300 and a Raynox DCR-250 mm 3 mm long; pedicels cylindrical, papillose, 6.5-8.2 × 0.5-1.2 mm; ovary brownish purple with green angles, 3-cristate, 1.9-2.2 × 3.0-3.9 mm, somewhat obconical, papilloseverruculose. Sepals pale greenish yellow variously marked with dark maroon spots, papillose, petals green or greenish yellow with dark purple marks, lip yellow splashed with mahogany or mahogany with yellow margin, column green with purple spots. Dorsal sepal ovate, subcarinate, 3-veined, concave, 4.0-4.5 × 8.5-9.0 mm including the tails, contracted into a thickened tail 1.7-2.1 × 0.7-0.8 mm, barely connate to the lateral sepals to form a gaping sepaline cup, subacute. Lateral sepals connate at the base for 0.7 mm; the blades ovate, ribbed in the middle, 3veined, oblique, unequal, 5.4-6.0 × 3.6-3.9 mm, contracted into thickened tails 2.2-3.1 × 0.7-0.9, the base decurved with a tranverse callus. Petals small, papillose, translucent, dolabriform 3.2 × 2.5-2.8 mm with thickenings in the lower margin near the base, the apex broadly obtuse, the lower margin with a decurved, obliquely triangular and truncate lobe. Lip long-unguiculate, papillose, the blade subquadrate, 2.8-3.0 × 2.3-2.5, the apex rounded, reflexed, the base above the claw with a pair of subacute, retrorse lobules, the disc with a pair of low calli below the middle, the claw broad 1.5-2.2 × 0.7-0.8 mm, bilobulate at the base, concave, hinged to the apex of the column-foot. Column subclavate, papillose 3.3-3.8 × 1.9-2.0 mm, hooded and denticulate at the apex, with two large, subacute, recurved, toothlike processes above the middle, 1.3 mm long, the foot 1.8-2.7 mm long. Anther papillose and stigma ventral, anther 0.9 mm long. Pollinia 2, yellow 0.7 mm long. Fruit a trialate, papillose capsule, 8.9 × 5.3 mm.

Distribution and habitat
Dryadella mocoana was known so far endemic for Colombia from the type specimen collected in the department of Putumayo [2]. Between 2019 and 2020, this species was collected at two locations in southern Ecuador, in the province of Zamora Chinchipe, widening its range of distribution and becoming the first record of the species for Ecuador. Currently, this species presents a discontinuous distribution and it is not excluded that could be also distributed along the Ecuadorian Amazon.
In the Zamora Chinchipe province, this species is found growing on tree trunks of lower montane forests between 1300 and 1700 m above sea level on the Amazonian slope of the Cordillera de los Andes. Two specimens were found at the steep hill-tops surrounding the town of Zamora with a ravine separating them. From the first specimen found herbarium material was prepared, the second specimen found at a lower elevation, was recorded with a photograph. The population of D. mocoana in Ecuador occurs in unprotected area not suitable for grazing and agriculture where selective timber extraction is common, hence it could be considered as threatened.

Phenology
This species has been observed with flowers from March to September.

Discussion
Dryadella mocoana is similar to Dryadella cuspidata Luer & Hirtz but differs from the latter by its wider sepals and shorter tails, the petals with a short and truncate process in the lower margin and the pair of taller and denticulate calli of the lip. The Ecuadorian specimens agrees well with the definition of D. mocoana in habit, foliar and flower size; meanwhile, the length of the peduncles and the color of the petals and lip is variable. In the original description of Luer [2], the calli of the lip are mentioned to be denticulate; nevertheless, this feature was not observed in Ecuadorian plants but is similar to what is found in D. cuspidata. This morphological similarity does not suggest there is hybridization process between both species because they do not grow sympatrically and mighte be related to the geographical isolation of the known populations of D. mocoana.