Introduction

Epidendrum L. (^{Linnaeus 1763}) is a neotropical genus that exhibits an extensive distribution range from South Carolina in the United States to Argentina (^{Hágsater & Soto 2005}). With an estimated 2400 species, Epidendrum showcases remarkable variability in both vegetative and floral characteristics (Hágsater et al. 2016, ^{Karremans 2021}, ^{Rincón-González et al. 2022}). Hágsater (¹⁹⁸⁵) introduced a classification system that organizes Epidendrum species into informal groups and subgroups to unravel the complexities of studying this genus. This system primarily relies on morphological features, with a strong emphasis on vegetative structures, particularly the architecture of the plant, simple or branching stems, the presence or lack of spathes at the base of the inflorescences, and these, racemose or paniculate, and flowering only once or repeatedly over several years. This approach has been widely adopted for taxonomic studies of the genus (^{Hágsater & Salazar 1993}, ^{Hágsater et al. 1999}, ^{Hágsater & Sánchez-Saldaña 2001}, ²⁰⁰⁴, ²⁰⁰⁶, ²⁰⁰⁷, ²⁰⁰⁸, ²⁰⁰⁹, ²⁰¹⁰, ²⁰¹³, ²⁰¹⁵, ²⁰¹⁶, ^{Hágsater & Santiago 2018a}, ^b, ²⁰¹⁹, ^2020a, ^b, ²⁰²¹, ^2022a, ^b, ²⁰²³, ^{Hágsater et al. 2016}, ^{Rincón-González et al. 2022}).

Initially, Hágsater (¹⁹⁸⁵) proposed to recognize the Arbuscula group, consisting of species that produce the new growth from one of the middle internodes of the previous growth, typically without branching and sometimes producing aerial roots. This group is further treated as the Arbuscula subgroup (^{Hágsater & Sánchez-Saldaña 2006: pl. 808}), characterized by a racemose, nutant inflorescence, membranaceous, colorful flowers, with long ovary, and a bicallose lip. Conversely, the Incomptum subgroup (^{Hágsater & Sánchez-Saldaña 2004: pl. 710}) is characterized by a racemose, nutant inflorescence, fleshy flowers with the perianth green, green-violet, purple, with entire to 3-lobed lip, extended to convex, orbicular, reniform to obreniform, bicallose, and a short ovary (Fig. 1). Subsequently, ^{Hágsater & Santiago (2018a)} published five species of Epidendrum classified within the “Incomptum group”, indicating a clear distinction between the Arbuscula and Incomptum groups, considering them as distinct lineages. Comparative morphological details of each group are shown in Table 1. Additionally, there is a geographical association with these groups, as the Arbuscula group is exclusive to Mexico and northern Mesoamerica, while the Incomptum group has a broader distribution, encompassing Mexico, Central America, the Caribbean, and South America (Hágsater et al. unpubl. data).

Photographs by Adam Karremans (A-B) and Rolando Jiménez (C-D).

Figure 1 Comparison between Epidendrum incomptum Rchb.f. (Incomptum group) (A, B) and Epidendrum arbusculum Lindl. (Arbuscula group) (C, D). 

Here, we propose a new species of Epidendrum from Colombia belonging to the Incomptum group. We provide a detailed description, illustrations, discuss its morphological similarities with other species, and offer information regarding its distribution, ecology and conservation status.

Materials and methods

During recent expeditions in 2018-2022, several field trips were made to the forests in Alto de Ventanas in Yarumal, Antioquia, within natural reserves owned and managed by Corporación Salvamontes, Colombia. We collected plant material that was deposited in the JAUM herbarium. The Colombian herbaria CAUP, COL, FMB, HUA, JAUM, JBB, MEDEL, PSO, and TOLI were also reviewed in search of more specimens of this species, and the virtual collections (digital photographs) of A, BHBC, F, HBG, K, MBM, NY, RB, and U. We followed the morphological species concept (^{De Queiroz 2007}). Photographs with scale were taken for study and description; we measured the organs with a digital caliper and observed the specimens under a stereomicroscope Motic SMZ 168. The information derived from the review of the specimens was verified at the AMO-DATA base (²⁰²¹), and was searched for possible duplicates or other unidentified specimens of the Incomptum group from the same general geographic area. A Lankester Digital Composite Plate (LCDP) was prepared from the photographic material available, and a botanical description, and the new species was compared with the most similar species in the Incomptum group.

Taxonomic treatment

Epidendrum pembertonii Rinc-González, E.Santiago & S.Vieira-Uribe, sp. nov. (Fig. 2-3A).

LCDP prepared by S. Vieira-Uribe, based on Vieira et al. #382.

A. Habit. B. Inflorescence. C. Flower. D. Dissected perianth. E. Column and lip, side view. F. Column, ventral and dorsal views. G. Pollinarium and anther cap, dorsal and ventral views.

Figure 2 LCDP of Epidendrum pembertonii Rinc-González, E.Santiago & S.Vieira-Uribe. 

Photographs by S. Vieira-Uribe (A), Adam Karremans (B-C) and Melissa Díaz (D).

A. Epidendrum pembertonii. B. Epidendrum brenesii Schltr. C. Epidendrum bisulcatum Ames. D. Epidendrum sotoanum Karremans & Hágsater.

Figure 3 Comparison of Epidendrum pembertonii Rinc-González, E.Santiago & S.Vieira-Uribe and most similar species. 

TYPE: Colombia. Antioquia: Municipio de Yarumal, Vereda Tobón, Finca Guasimal, 2080 m. 25 Julio 2022. Sebastian Vieira et al. #382 (holotype: JAUM).

Diagnosis: Epidendrum pembertonii is similar to E. brenesii Schltr. (^{Schlechter 1923}) but easily distinguished by having two, elliptic (vs. 3-5, oblong) larger leaves (5.2-6.0 × 2.5-2.7 vs. 2-8 × 1.3-2.5 cm), longest inflorescence (7.2 vs. 2-4 cm), tepals greenish yellow with a brown tinge (vs. light green with purple tinge to deep purple), red lip with yellow to red calli (vs. purple tinge to deep purple lip with yellow-greenish calli), greenish yellow column (vs. green), the dorsal sepal narrowly obovate, 5-veined (vs. obovate-elliptic, 3-veined), the lateral sepals obliquely elliptic, 5-veined (vs. obovate-elliptic, 3-veined), the lip smooth, apex apiculate, (vs. velutinous, short setose, apex sometimes slightly 4-lobed) and the longer column (9-10 vs. 7-8 mm), straight, apex arching upwards (vs. arching downwards).

Epiphytic, sympodial, erect to pendulous herb 78 cm tall, new stems produced from a sub-apical internode of previous stem. Roots fleshy, from base of primary stem. Stems 8-13 × 0.3-0.5 cm, cane-like, terete, erect to pendulous when weight in old plants makes them hang from the roots, simple. Leaves 2, aggregate towards the apex of the stem, spreading, alternate; sheaths 0.32-0.65 × 0.3-0.5 cm, tubular, striated, reddish-brown; blades 5.2-6.0 × 2.5-2.7 cm, elliptic, obtuse, coriaceous, green, concolor. Spathe lacking. Inflorescence 7.2 cm long, apical, from the mature stem, racemose, arcuate; peduncle 2.2 × 0.43 cm, laterally compressed, green; rachis 5 cm long, arching-nutant. Floral bracts 5-6 mm long, much shorter than ovary, decreasing in size towards apex of the rachis, triangular, acute, embracing. Flowers ca. 18, opening in succession, until most open at the same time, resupinate, greenish yellow tinged with brown, lip red with calli yellow to red, column greenish yellow, slightly tinged reddish brown, anther yellow; fragrance none detected. Ovary 12-15 × 2.2-2.8 mm, slightly inflated behind the perianth, terete, furrowed, somewhat arcuate. Sepals free, fleshy, 5-veined, margins entire; dorsal sepal 13.5 × 6.0 mm, spreading, narrowly obovate, sub-rounded, minutely apiculate; lateral sepals 13.1 × 7.5 mm, partly spreading, obliquely elliptic, obtuse, apiculate. Petals 13.5 × 4.2 mm, free, spreading, oblanceolate, apex obtuse, 3-veined, margin entire. Lip 9-12 × 15.2-17.0 mm, united to column, fleshy, convex, smooth, wider than long, reniform, base cordate, apex emarginate, margin entire, spreading; bicallose, calli globose, slightly separate, disc with a thick, low rib running at the apex, reaching apical sinus of lip. Column 9-10 mm long, somewhat thick towards the apex, truncate, straight, apex arching upwards. Clinandrium-hood reduced, margin entire. Anther 1.9 × 2.3 mm, sub-globose, apex minutely apiculate, apical surface minutely papillose, 4-celled. Pollinia 0.87 × 0.66 mm, ovoid; caudicles granulose, shorter than pollinia; viscarium semi-liquid. Rostellum apical, slit. Lateral lobes of stigma about half length of stigmatic cavity. Cuniculus shallow, slightly penetrating ovary, narrow, smooth. Capsule not seen.

Eponymy: We dedicate this species to Robert W. Pemberton, an entomologist and botanist, as well as a generous donor who contributed to the expansion of the Los Magnolios Natural Reserve, which protects the habitat of the new species.

Habitat and ecology: Known only from Colombia, specifically from the north slope of the Cordillera Central in Antioquia. It grows as an epiphyte at 2080 m of elevation in premontane wet forest. A single plant has been found, thriving near an open pasture on the main trunk of a medium sized tree located along a small creek at approximately 2 m above the ground and in partial shade. It grows together with several other orchid species, including Maxillariella lawrenceana (Rolfe) M.A. Blanco & Carnevali (^{Blanco et al. 2007}) and Restrepia pelyx Luer & R.Escobar (^{Luer & Escobar 1982}). The plant has been observed flowering during every month of the year, with a single inflorescence lasting 2-3 months.

Conservation status: DD. Deficient Data. This species is pparently endemic to the Alto de Ventanas region of Yarumal-Antioquia, located in the north of the central Andes. Thus far, it has been exclusively found in the Los Magnolios Natural Reserve, owned and managed by Corporación Salvamontes. The reserve protects 770 hectares of habitat in the Alto de Ventanas area. However, this region has experienced significant deforestation, with approximately 70% of its forests lost due to the expansion of pastures for dairy farming (^{CORANTIOQUIA 2020})

Morphological affinities: Epidendrum pembertonii belongs to the Incomptum Group which is characterized by the successive lateral growths produced from the middle of the previous growth, the few leaves aggregate towards the apex of the stems, a short apical, racemose, nutant inflorescence, with fleshy, green, yellow, yellow-greenish, violet-green, to black flowers, short ovaries, and the lip entire to 3-lobed. The species is recognized by having 2 elliptic leaves, inflorescence of 7.2 cm long, the combination of color in the flowers, sepals 5-veined, petals oblanceolate, lip reniform, 9-12 × 15.2-17.0 mm and column somewhat thick towards the apex, straight, apex arching upwards, 9-10 mm long. Epidendrum brenesii is the most similar species, differing in having 3-5 oblong leaves (vs. 2, elliptic), shorter inflorescence (2-4 vs. 7.2 cm), 3-veined sepals (vs. 5-veined), Column arched downwards, 7-8 mm long (vs. straight, apex arched upwards, 9-10 mm). Epidendrum bisulcatum Ames (^{Ames 1923}) differs in having oblong leaves (vs. elliptic), inflorescence 3.8 cm long (vs. 7.2 cm), dorsal sepal oblong, 3-nerved (vs. narrowly obovate, 5-nerved), lip suborbicular, retuse to rounded apex (vs. reniform, emarginate, apiculate). Epidendrum foldatsii Hágsater & Carnevali (^{Hágsater & Salazar 1993}) is characterized by an inflorescence 2 cm long (vs. 7.2 cm), ovary 5-7 mm long (vs. 12-15 mm), sepals 3-veined (vs. 5-veined), petals 1-veined (vs. 3-veined), lip obreniform (vs. reniform) and column slightly sigmoid, 3 mm long (vs. straight, apex arched upwards, 9-10 mm). Epidendrum sotoanum Karremans & Hágsater (^{Karremans & Hágsater 2009}) is characterized by an inflorescence 2 cm long (vs. 7.2 cm), cuniculus short, without penetrating the ovary (vs. shallow, slightly penetrating ovary), sepals 3-4 veined (vs. 5-veined), petals narrowly-obovate (vs. oblanceolate), lip superficially glabrous but with low rounded papilla, 10-17 × 20-30 mm (vs. smooth, 9-12 × 15.2-17 mm). The mentioned differences with the most similar species are expanded and illustrated in Table 2 and Figure 3.