Altensteinia tenebrosa, Mart´, Claudia M., Zanotti, Christian A. & Scrocchi, Gustavo J., 2020

Mart´, Claudia M., Zanotti, Christian A. & Scrocchi, Gustavo J., 2020, Aa (Orchidaceae) of Southern Central Andes: Taxonomy, Nomenclature, and a New Species with Dark Flowers, Systematic Botany (Basel, Switzerland) 45 (4), pp. 760-766 : 762-765

Aa tenebrosa C. M.Mart´ın & G. J.Scrocchi sp. nov. TYPE: ARGENTINA. Salta: Dep. Santa Victoria, Ruta Provincial 7, de Santa Victoria a Lizoite, 22°16 0 180S, 65°05 0 250W, 3730 m, 15 February 2009, Zuloaga et al. 10773 (holotype: SI092427 !; isotypes: CORD!, CTES0043314 !) .

Plants small, terrestrial. Roots fleshy, fasciculate, pubescent. Leaves basal, linear-lanceolate, acute to acuminate, coriaceous, 8–13 3 0.3–0.5 cm. Inflorescence erect, 10–17 cm long, pubescent, enclosed by hyaline and diaphanous sheaths, terminated in a short spike, formed by few flowers, 1–3 cm long, rachis pubescent. Floral bracts ovate to subulate, acute, margins slightly erose at the apex, 4–5 3 2.5–2.9 mm, reflexed, surpassing the flowers, brown with whitish edges. Black and brown-greenish flowers. Dorsal sepal ovate, acute, erose at the apex, glabrous, 1.5 3 1.1 mm. Lateral sepal oblong, obtuse, entire, glabrous, 2 3 0.8 mm. Petals ovate-lanceolate, acute, margin slightly erose, 1.8 3 1 mm. Lip cucullate, with a narrow opening, margins involute, deeply laciniate, 2.7 3 1.5 mm (natural position). Column short, emarginated, glabrous. Ovary sessile, globose, pubescent, 1.5–2 mm long. Figures 1 , 2 .

Distribution and Habitat — Aa tenebrosa is only known from the type locality, Serran´ ıa de Santa Victoria (Salta, Argentina). This species grows on hillsides, between 3500–3730 m a. s. l., in Yungas Montane Grasslands associated with rocky outcrops. This region has high diversity, and is biogeographically important due to its high number of endemic species (Mart´ın et al. 2017; Mart´ın 2019).

Aa tenebrosa shares its habitat with species such as Mandevilla pentlandiana (A.DC.) Woodson ; Philibertia lysimachioides (Wedd.) T.Mey. ( Apocynaceae ); Chuquiraga longiflora (Griseb.) Hieron. , Hieracium argentinense Zahn , H. neofurcatum Sleumer , Lucilia recurva Wedd. , Onoseris hastata Wedd. , Senecio crepidifolius DC. ( Asteraceae ); Gaultheria erecta Vent. , Gaylussacia cardenasii A.C.Sm. ( Ericaceae ); Brachyotum microdon (Naudin) Triana ( Melastomataceae ); Cyclopogon oliganthus (Hoehne) Hoehne & Schltr. and Odontorrynchus castillonii Hauman ( Orchidaceae ); Agalinis fiebrigii (Diels) Darcy (Orobranchaceae); Briza uniolae (Nees) Nees ex Steud. , Cortaderia hieronymi (Kuntze) N.P.Baker et H.P.Linder , Danthonia secundiflora J.Presl. , Elymus scabriglumis (Hack.) A’.Löve, and Jarava ichu Ruiz et Pav. var ichu ( Poaceae ); Thalictrum venturii Boivin ( Ranunculaceae ); Nierembergia rivularis Miers ( Solanaceae ); Barbaceniopsis boliviensis (Baker) L.B.Sm. ( Velloziaceae ); Viola micranthella Wedd. and V. rodriguezii W.Becker ( Violaceae ); among others (pers. obs.). Flowering plants have been recorded in February.

Etymology —From the Latin tenebra (darkness, shadow, obscurity) in reference to the colour of the flowers.

Observations — Aa tenebrosa is recognized as a new species based on a combination of morphological features that distinguish it from another species with dark flowers, A. leucantha (Rchb.f.) Schltr , endemic of the northern Andes ( Colombia, Venezuela, and Ecuador) (see Szlachetko and Nowak 2014; Nowak 2019). The new species is distinguished by the floral segments up to 2 mm (vs. above 3 mm in A. leucantha ), pubescent rachis (vs. glabrous in A. leucantha ), and pilose ovary (vs. obscurely pilose at the base of lateral sepals in A. leucantha ). Finally, Aa tenebrosa grows in Yungas Montane Grasslands (Southern Central Andes), and A. leucantha grows in paramo (Northern Andes).

Figures

FIG. 1. Aa tenebrosa. A. Type. B. Plant. C. Inflorescence.

FIG. 2. Aa tenebrosa. A. Plant. B. Inflorescence. C. Flower, frontal view. D. Flower, dorsal view. E. Flower, lateral view. F. Lip and ovary, lateral view. G–G’. Lateral sepals. H–H’. Dorsal sepal. I–I’. Petals. J. Gynostemium. Drawn from Zuloaga et al. 10773 (SI).