Scyphostelma rotorum Meve & Y. M. Pineda, 2023

Pineda, Yam M., Keller, Héctor A., Balderrama-Torrico, José A., Meve, Ulrich, Nürk, Nicolai M. & Liede-Schumann, Sigrid, 2023, Phylogenetics in Scyphostelma (Apocynaceae: Orthosiinae) and description of new species, Willdenowia 53, pp. 83-112 : 94-96

5. Scyphostelma rotorum Meve & Y. M. Pineda , sp. nov. – Fig. 3 , 9 .

Holotype: Peru, Cusco, Paucartambo, Valle del Pilcopata, roadside near Pillahuata , at km 121–126 , 13°10'S, 71°30'W, 2500 m, 14 Dec 1983, R. B. Foster & T. S. Wachter 7498 ( USM!; isotype: MO- 423395 ) .

Diagnosis — Similar to Scyphostelma harlingii (Morillo) Liede & Meve but with gynostegial stipe (and corona) reaching just 1/3 of length of gynostegium (vs at least 1/2 of length in S. harlingii ), corona lobes green, extending horizontally into c. 0.8 mm long, spreading, subrectangular tubes open at bottom (vs corona lobes white to purplish, spreading to 0.3 mm in S. harlingii ).

Morphological description — Twining plants; stems bright brown, with scattered, retrorse appressed trichomes; internodes of long shoots 55–62 × 1.2–1.5 mm, internodes of short shoots 20–35 × 0.7–1 mm. Leaves discolorous; petiole 4–6 mm long, channelled, densely pilose on upper margin; lamina lanceolate, 15–40 × 4–7 mm, base rounded to subtruncate, apex acute to acuminate; abaxial surface scattered pilose, densely pilose on main veins, adaxial surface with scattered trichomes, with 2 or 3 conic colleters at base; venation brochidodromous with 4–7 pairs of secondary veins. Inflorescences extra-axillary, alternate, with 3–7 flowers per cyme, at most 2 in simultaneous anthesis; peduncle filiform, 25–45 × 0.4–0.5 mm, glabrous or nearly so; bracts ovate, c. 0.7 × 0.4 mm, abaxially pilose. Flowers: pedicel filiform, 15–25 × 0.2–0.3 mm, glabrous; calyx lobes ovate, c. 0.8 × 0.4 mm, abaxially pilose, margin ciliate, apex subacute; corolla dark purple, rotate, tube c. 2.5 mm in diam., lobes reflexed, oblong-lanceolate, 4–4.5 × 1.2– 1.7 mm, abaxially glabrous, adaxial base with scattered trichomes, adaxial distal half covered with short, verrucose trichomes (becoming densely pilose toward tip). Gynostegial corona green with purplish tinge, c. 2 mm in diam., lobes connected to gynostegial stipe, arching upright, c. 0.8 mm high and then horizontally extending to c. 0.5 mm, forming spreading, subrectangular tubes open at bottom; gynostegium stipitate, c. 1 × 1.4 mm, c. 2 × as long as corona lobes, basally narrowing, stipe c. 0.5 × 1 mm; anthers subrectangular, c. 1.1 × 0.8 mm, anther appendages deltate, c. 0.45 × 0.7 mm, translucent, appressed to style head, guide rails c. 0.8 mm long, narrowly triangular, inclined. Style head and pollinaria not seen. Follicles and seeds not seen.

Phenology — The single gathering documented was found flowering in December.

Etymology — The specific epithet refers to the unusual gynostegial corona with the single corona lobes reminiscent of rotor blades.

Remarks — Scyphostelma rotorum appears to belong to the S. harlingii group for morphological reasons. Particularly in the filiform inflorescence structures and the corolla, S. rotorum closely resembles S. harlingii , differing only in minor quantitative aspects. Unfortunately, we failed to separate pollinaria. In addition, leaf shape is virtually identical in the two species, even though the leaves of S. rotorum are much smaller (15–40 × 4–7 mm vs 30–70 × 7–27 mm in S. harlingii ). Scyphostelma harlingii occurs also in Peru ( Fig. 3 ; two gatherings, see above); therefore S. rotorum could be regarded as the most southern extension of S. harlingii (into Cusco). However, as we did not observe any floral variability in S. harlingii , and as the gynostegial dimensions and coronal structures, though based on the same general structure, are so different from each other in terms of corona lobe shape, size and colour, we propose this as new species endemic to Valle del Pilcopata.

Figures

Fig. 3. Distribution map of Scyphostelma bolivianum (diamonds), S. erikseniae (circles), S. gra- cile (stars), S. harlingii (upright triangles), S. rotorum (square) and S. solomonii (inverted trian- gle). – Map created in QGIS (QGIS Development Team 2009).

Fig. 9. Scyphostelma rotorum – A: flowering branch; B: inflorescence bract; C: flower; D: gynostegium and corona (reconstructed). – A–D from the holotype, R. B. Foster & T. S. Wachter 7498 (USM). – Drawn by U. Meve.