Pabstiella assisii N. Gut., E.C.Smidt & Toscano, 2023

Morales, Nicolás Gutiérrez, Brito, A. L. V. Toscano De & Smidt, Eric De Camargo, 2023, Novelties and nomenclatural notes in Pabstiella (Orchidaceae) from the Brazilian Atlantic Rainforest of Bahia and Espírito Santo, Phytotaxa 625 (2), pp. 161-179 : 167-171

Pabstiella assisii N. Gut., E.C.Smidt & Toscano , sp. nov.

( Figures 5–7A )

Type: — BRAZIL. Espírito Santo: Santa Teresa , 500–600 m, collected in April 2020, flowered in cultivation at Curitiba, Paraná, by Marcos Klingelfus, 20 May 2023, N. Gutierrez 258 (holotype: UPCB! in spirit) .

Similar to P. decurva Luer & Toscano (2011: 371) , but the new species is distinguished by the non-resupinate, yellow flowers (vs. resupinate, pale green to pale yellow flowers), with irregular, vinaceous spots in sepals and petals (vs. unspotted perianth), sepals glabrous (vs. sepals minutely pubescent within), the dorsal sepal is lanceolate, acute (vs. oblong, obtuse), the petals have apiculate apex (vs. petals with rounded to truncate apex), and the lip has three keels along the veins in the ventral surface (vs. lip without keels on the ventral surface). Furthermore, the color of column and anther is a contrasting dark red in the new species, while P. decurva displaces a whitish color.

Description:— Plant small, epiphytic, caespitose, occasionally prolific, up to 7.3 cm including the inflorescence, roots slender, flexuous, to 0.5 mm in diameter. Ramicauls terete, 0.5–1.5 cm long, enclosed by 2–3, ribbed, oblique, acute sheaths. Leaves broadly elliptical, coriaceous, with both surfaces verruculose, the underside densely purple spotted, obtuse, the apex minutely emarginate with a central mucron, 1.2–1.9 × 0.7–0.9 cm, the base cuneate into a petiole ca. 2.0 mm. Inflorescences (1–4) per ramicaul, in a raceme with dark red rachis, with nearly ten successive, not resupinate flowers, emerging 1.0–2.0 mm below the abscission layer, up to 6 cm, with a small bract at the base and two tubular, oblique, acute bracts along the peduncle, each 3.0 mm long, floral bracts oblique, acute, ca. 1.5 mm long. Pedicel 2.0–5.0 mm long. Ovary shallowly sulcate, slightly arcuate, ca. 1 mm long. Flowers no resupinate, sepals yellow, vinaceous along the veins and few, small vinaceous stains. Dorsal sepal oblong-lanceolate, the basal half convex, the apical half reflexed, 3-veined, acute, 5.5–6.0 × 1.3 mm. Lateral sepals slightly carinate, each 3-veined, connate ca. 3.7 mm, forming an oblong, concave synsepal, with recurved, acute apices, 5.0 × 2.4 mm unexpanded. Petals yellow, vinaceous along the vein, with several irregular stains, lanceolate-oblique, asymmetrical, 1-veined, verrucose towards the apex in both surfaces, mainly in the external surface, apiculate, 3.2–3.3 × 1.1–1.2 mm. Lip yellow, with vinaceous stains concentrated along the margins, hinged to the column foot, oblong, bilobate, the lobes erect, unguiculate when expanded, arcuate, verruculose, the dorsal surface with a pair of longitudinal, submarginal calli, the ventral surface with 3-keels along the veins, the keels minutely papillate, the apex truncate, with a pair of small lobules at the corners, the margins erose, 1.3 × 0.8 mm unexpanded. Column dark red, semiterete, slightly arcuate, minutely and densely pubescent in the ventral surface, narrowly winged, the apex denticulate, 2.0–2.3 × 0.6–0.8 mm, the anther and stigma ventral, the rostellum rectangular, rose, the foot ca. 0.5 mm long. Anther dark red, whitish along the margins, triangular, hooded, pollinarium composed of two, yellow, obovate pollinia united by a caudicle. Fruit capsule, not observed.

Distribution and ecology:— the species has only been found in humid, mist forests in the municipality of Santa Teresa, in Espírito Santo ( Figure 4 ). The epiphyte plants were growing partially exposed to sunlight in the same area as other orchid species such as P. armeniaca (Barb. Rodr.) L. Kollmann (2010: 96) , P. lueriana Fraga & L. Kollmann (2010: 172) , Epidendrum vesicatum Lindl. (1838: Misc. 50), and Cattleya praestans (Rchb. f. 1857: 336) Van den Berg (2008: 10) . The main blooming period occurs during the transition from summer to fall, specifically from March and June.

Etymology:— dedicated to Daniel de Assis Rodrigues, who first discovered and cultivated this species.

Additional material examined (paratype):— BRAZIL. Espírito Santo: Santa Teresa , 500–600 m, collected by Daniel Assis in April 2020, flowered in cultivation at Curitiba, Paraná, by Marcos Klingelfus, 20 May 2023, N. Gutierrez 291 ( UPCB! in spirit) .

Taxonomic discussion:— Pabstiella assisii shares several morphological features with P. decurva ( Figure 7B ), to such an extent that when comparing sterile plants, they may appear indistinguishable from each other. They possess an overall similar size, broadly elliptical and obtuse, coriaceous leaves that are suffused with purple in the underside, exhibiting a verruculose texture. The inflorescences of both species surpass the leaves, and the sepals are stripped along the veins. The dorsal sepal is recurved, the petals have the apex verrucose-verruculose, the lip is small and bilobate, arcuate and truncate, with a pair of submarginal calli. The column is densely short-pubescent in the ventral surface and denticulate at the apex.

Pabstiella assisii can be distinguished from P. decurva by its non-resupinate, yellow flowers (vs. resupinate, pale green to yellow flowers), with irregular, vinaceous spots in sepals and petals (vs. unspotted perianth). The sepals of P. assisii are glabrous (vs. sepals minutely pubescent within), the dorsal sepal is lanceolate, acute (vs. oblong, obtuse), the synsepal is oblong (vs. obovate). The petals of P. assisii are asymmetrical and have an apiculate apex (vs. slightly asymmetrical, rounded to truncate apex). Additionally, the ventral surface of the lip in P. assisii bears three papillose keels along the veins (vs. lip without keels on the ventral surface). Another distinguishing characteristic is the color of the column and anther, with the new species having a dark red color while P. decurva has a whitish color.

Both Pabstiella assisii and P. decurva are easily distinguishable from other species in the genus due to the small size, verruculose leaves suffused with purple in the underside, and the small, bilobate lips with truncate apices. Pabstiella muricatifolia Fraga & L. Kollmann (2010: 174) , another endemic species from Espírito Santo, also has leaves with verruculose surfaces. However, the leaves of P. muricatifolia are concolor and acute, and the ramicauls are very short, to 0.75 cm long (vs. leaves suffused with purple in the ventral surface, with obtuse apex, and ramicauls to 1.5 cm in P. assisii ). The differences between the latter two species become even more remarkable when comparing the flowers, particularly the lip, which is considerably bigger, to 3.1 mm long, and 3-lobed in P. muricatifolia (vs. lip to 1.3 mm, bilobulate, in P. assisii ). It is worth noting that the small, bilobate lip characterizing P. assisii and P. decurva is unique to these taxa, representing an exception within the genus, which typically has a 3-lobed lip with rounded apex.

Due to the remarkable similarity with Pabstiella decurva , a species included in the phylogenetic analysis of the genus, we suggest that the new species belongs to the Ornithoides section. This particular lineage comprises a heterogeneous group of species that is challenging to define morphologically. To gain a better understanding of its delimitation, further molecular studies should incorporate unsampled species (Gutierrez Morales et al. 2021).

Figures

FIGURE 4. Distribution map of the three new species of Pabstiella.

FIGURE 5. Illustration of Pabstiella assisii. A. Habit. B. Flower in its natural position. C. Perianth, with both views of one petal. D. Ovary, column and lip, lateral view. E. Expanded lip, dorsal view. F. Expanded lip, ventral view. G. Column, ventral view. Illustration by Nicolás Gutiérrez Morales from the holotype.

FIGURE 6. Lankester Composite Dissection Plate of Pabstiella assisii. A. Habit, detail in the underside of the leaf. B. Flower, vertically inverted. C. Dissected perianth. D. Ovary, column and lip, lateral view. E. Lip. F. Column, ventral view. G. Anther cap and pollinarium. Photographs by Nicolás Gutiérrez Morales from the holotype.

FIGURE 7. Vegetative and floral comparison. A. P. assisii B. P. decurva. Photographs by Nicolás Gutiérrez Morales.