Stelis kolomeitsevae Koval & Karremans, 2025

Koval, Vladimir A. & Karremans, Adam P., 2025, Stelis kolomeitsevae (Orchidaceae: Pleurothallidinae): a new species from Pichincha province, Ecuador, Phytotaxa 697 (3), pp. 274-281 : 275-279

Stelis kolomeitsevae Koval & Karremans , sp. nov. ( Figures 1–2 )

Type: — ECUADOR. Pichincha: Mindo Forest, ca. 1600 m elev., 28 August 2020, unknown collector. Flowered in cultivation at the fund collection greenhouse of the Main Botanical Garden, named after N. V. Tsitsin of the Russian Academy of Sciences, prepared on 4 November 2024 ( holotype: MHA [#VK0022] spirit collection) .

The new species is similar to Stelis lancea Lindley (1859: 3) , but can be distinguished from it by its shorter leaves (4.0– 6.5 cm long vs. 6.0–10.0 cm long), shorter petiole (0.5–1.0 cm vs. 1.5–2.0 cm), the loosely flowered inflorescence up to almost three times longer than the leaf ( vs. inflorescence dense, barely surpassing the leaf), longer floral bracts ( 2.8–3.2 mm vs. 1.5 mm) and pedicel ( 2.8 mm vs. 1.0 mm), smaller (1.5–1.7 × 1.2–1.4 vs. 2.0–2.5 × 2.0), glandularpapillose ( vs. microscopically pubescent) sepals, and shorter (0.6 vs. 1.0 mm) column with a 5-lobed clinandrium ( vs. 3-lobed).

Description:—Epiphytic, scandent, ascending-repent herb, up to 26 cm high including the inflorescence. Rhizome 3 mm in diameter, with a spacing of 0.8–1.2 cm between adjacent stems. Roots slender, flexuous, yellowish, ca. 1 mm in diameter. Stems straight, terete, composed of two internodes; the upper internode 1.5–2.0 cm long, the lower internode 0.8–1.2 cm long, each 2–3 mm in diameter; both internodes completely covered by narrow, scarious, tubular, obtuse, carinate, and mucronate sheaths; lower sheath eventually falling off, the upper sheath persisting. Leaves fleshy, coriaceous, with a single midvein that is abaxially carinate, elliptic, rounded, emarginate and mucronate at the apex, 4.0–6.5 × 1.0– 1.5 cm including a conduplicate petiole 0.5–1.0 cm long. Inflorescence arising from the annulus of the stem, up to 18 cm long, a single erect, strict, many-flowered (16-24 flowers) raceme; flowers open simultaneously, while apical ones remain in bud as fruits develop at the basal part; pseudopeduncle 6–9 cm long, 1 mm in diameter, enclosed at the base by a scarious, conduplicate, acute, carinate, shortly apiculate spathaceous bract 5–6 mm long, with 3–4 additional bracts similar to the floral bracts, measuring 3.4–4.5 mm long. Floral bracts obliquely funnel-shaped, apiculate, carinate, 2.8–3.2 mm long. Ovary induplicate, slightly arching, 1.0– 1.2 mm long, pedicel 2.3 mm long. Flowers greenish-yellow, 2.6–2.9 × 2.7–3.2 mm. Sepals fleshy, broadly ovate, obtuse, 1.5–1.7 × 1.2–1.4 mm, connate at their bases by 0.5–0.8 mm before extending freely, 3-veined, minutely glandular-pilose on the adaxial surface. Petals porrect, quadrangular-reniform, broadly rounded, shallowly concave, 1.0–1.2 × 1.1–1.2 mm, 3- veined, fleshy-thickened toward the apex. Lip fleshy-thickened, transversely hemispherical-subquadrate, subrounded, minutely emarginate at the apex, truncate at the base, 0.5 × 1.1 × 0.6 mm, concave near the apex, hinged to the base of the column; margin slightly erect and granulose on the abaxial surface, especially toward the apex; on the adaxial surface with a medial and triangular callus that abruptly narrows and extends toward the apex, the callus 0.5 mm at its narrowest point, 1.3 mm in the middle, expanding to 1 cm at its base, and its depth is 2.5 mm from the center to the base. Column erect, broadened toward the apex, 0.6 × 0.8 mm, clinandrium 5-lobed, oriented forward. Stigma apical, formed by two semicircular-reniform lobes, each 0.45 mm wide; rostellum suberect, obtuse, provided with an axial and abaxial crest. Anther cap apical, hemispherical. Pollinia 2, pyriform, yellow, 0.4 mm long, joined in a fluid viscidium at the tip of the rostellum. Capsule ellipsoid, trigonous, 13.0 × 4.0 mm, with the dry segments of the perianth persistent.

Distribution and ecology:—Only known from the type locality in Ecuador, where it was found in the cloud forests of Mindo Forest, Pichincha province ( Figure 3 ). It grows as an epiphyte at an elevation of 1600 m, observed on the bark of a broken branch. The flowering period (in greenhouse conditions) occurs from late September to late November.

Etymology: —The epithet honors Galina L. Kolomeitseva, a distinguished orchidologist and the first author’s teacher and mentor, whose guidance and expertise have profoundly shaped his academic career.

Taxonomic discussion: — Stelis kolomeitsevae is morphologically similar to S. lancea and S. loejtnantii Luer & Endara in Luer (2004: 160), which also have a repent habit. In its floral morphology, the new species is similar to S. protracta Luer & Hirtz in Luer (2002: 56) and S. scitula Luer & Hirtz in Luer (2007: 48). In contrast, S. kolomeitsevae differs from S. lancea and S. loejtnantii by its narrower, ovate leaves (4.0–6.5 × 1.0– 1.5 cm vs. 6.0–10.0 × 1.5–2.5 cm) and shorter ramicauls ( 2.3–3.2 cm vs. 5.0–9.0 cm). In floral morphology, it is distinguished from S. protracta and S. scitula by its loosely arranged flowers in an erect, acropetal raceme ( 15–18 cm long), while S. scitula has congested, secund racemes. The clinandrium of S. kolomeitsevae is 5-lobed, in contrast to the 3-lobed structure in the other species. The lip is transversely hemispherical-subquadrate with an emarginate apex, whereas in the other species, it is subquadrate and concave anteriorly, with a broadly rounded or minutely apiculate apex. Additionally, S. kolomeitsevae features a distinct triangular callus extending from the center to the base of the lip, whereas the shape of the callus varies among the other species. A comparative summary of these distinctions is provided in Table 1 .

Figures

FIGURE 1. Composite Digital Plate of Stelis kolomeitsevae. A. Habit, note the tridentate leaf apex (close up view within white circle). B. Flower, note the papillae (close up view within white circle). C. Dissected perianth, without lip. D. Column with ovary; from left to right: dorsal, ventral, and lateral views. E. Lip and lip with column, frontal views F. Anther cap and pollinarium. G. Inflorescence, note the bract (close up view within white circle). Images by V.K.

FIGURE 2. SEM details of flowers of Stelis kolomeitsevae. A. Flower. B. Anther cap. *: viscidium, close up from (A). C. Lip with column (Digital camera). D. Stigmatic surface of the column without anther cap and pollinarium, note the rudimentary lateral lobes of the rostellum (white arrows). E. Pollinium-support cells, close up from (D). F. Ultrastructure of cells at the boundary between the adaxial and abaxial surfaces of the lip, close up from (G). G. Lip, frontal view. H. Lip in ¾ view (Digital camera). I. Central callus on the lip with a complex structure, composed of numerous papillose outgrowths, close up from (G). Images by V.K.

FIGURE 3. Map of Ecuador with highlighted provinces, showing the type locality of Stelis kolomeitsevae Koval & Karremans (yellow circle).