Microchilus dasilvae Engels & E.C.Smidt

Engels, Mathias E. & Smidt, Eric C., 2022, Microchilus dasilvae: a new species of Goodyerinae (Orchidaceae) from Southeastern Brazil, Phytotaxa 555 (3), pp. 252-258 : 253-256

Microchilus dasilvae Engels & E.C.Smidt sp nov. ( Figures 1–2 )

Type: — BRAZIL. São Paulo: Ibiúna. Vegetative material received from Marcos Aurélio da Silva and cultivated until flowering, fl., 24 September 2021, M.E.Engels 9306 (holotype MBM!; isotypes HCF!; RB!; SP!; UPCB!) .

Similar to Microchilus decorus and Microchilus metallescens , differs in lip with trilobed mesochile, yellow, with acute lateral lobes; and by the broad-ovate epichile, about the same width as the mesochile when flattened.

Description:— Humicolous herb, up to 30-35 cm tall. Roots 6–16 × 1–2 mm, cylindrical, hairy, white. Rootbearing portion of stem 5–8 × 2–4 mm, cylindrical, green; internodes 1.5–2.1 cm long, one root per internodes; foliate portion of stem 11.5–13.2 × 0.3–0.5 cm, cylindrical, 6–9 foliate, green; internodes (0.7)– 1–2.4 cm long. Leaves petiolate, lanceolate to narrow-lanceolate; petiole + sheath 1.1–1.7 × 0.8–1.2 cm amplective, pale-green; blade 2.0-4.2 × 0.7-1.9 cm, dark-green, discolourous, base decurrent, margin entire and smooth, acute. Inflorescence simple, erect, racemose, (3)–19–27–flora; peduncle 11.1–12.7 × 0.1–0.2 cm, pubescent, greenish-brown; peduncle bracts 0.9–1.3 × 0.2–0.6 cm, lanceolate, base acute or amplective, margin entire to ciliate, acute, brown, in the basal portion of peduncle amplective and the distal portion free; rachis 3.5–5.8 × 0.1–0.15 mm, pubescent, green; floral bracts 5–9 × 1–3 mm, lanceolate, acute, margin entire and ciliate, acute, light-brown. Flowers with ovary + pedicel ca. 7 × 1.5 mm, sub-oblanceoloid, hairy, green; dorsal sepal ca. 4 × 2 mm, oval, base cuneate to acute, margin entire, apex rounded, abaxial face hairy, white with central longitudinal bilinear brown macula; lateral sepals ca 4 × 2 mm, elliptical, slightly asymmetric, acute base, entire margin, obtuse-rounded apex, hairy abaxial face, white with bilinear central longitudinal macula; petals ca. 4 × 1 mm, narrow-elliptical, sub-falcate, slightly asymmetric, base acute, margin entire, apex obtuse, glabrous, white; lip 13–13.5 × 2 mm, subdivided; hypochile ca. 7 × 1 mm, narrow-ellipsoid, cylindrical, apex rounded, glabrous, calcariform, white; mesochile ca. 4 × 2 mm, obovate, margin entire, yellow, lateral lobes acute; epichile ca. 2–2.5 × 2 mm, broad-ovate, base acute, margin entire, apex obtuse and apiculate, white. Column ca. 4 × 1.25–1.5mm; stigma ca. 0.3 × 1 mm, obsemilunate, bilobed; rostellum ca. 2 mm long, deltoid and long narrow apiculate, acute; rostellar remnant with truncated scar; anther ca 1 × 0.5 mm, elliptical-ovate, brown, apiculate; pollinia 2, ca. 1 mm long, obclaviform, slightly flattened, longitudinally grooved, white. Fruits and seeds not seen.

Distribution and ecology:— Occurs as humicolous in the forest understory, in an ecotonal region between Ombrophilous Dense Forest and Semideciduous Seasonal Forest, in the Atlantic Forest Domain. It flowered in cultivation between September and October.

Etymology:— The specific epithet is in honour of the discoverer of a new species in the field, a Brazilian Orchidologist Marcos Aurélio da Silva.

Additional specimen examined (paratype):— BRAZIL. São Paulo: Ibiúna. Material cultivated until flowering and kindly provided by Marcos Aurélio da Silva , fl., 05 October 2020, M.E.Engels 8231 (MBM!; RB!, UPCB [spirit]!) .

Conservation status:— According to IUCN criteria (2017), M. dasilvae falls under Data Deficient (DD). More studies are necessary to locate more populations and estimate the number of mature individuals. The area where the species was discovered suffers from anthropological disturbance, including real estate pressure, making the species naturally threatened due to habitat loss.

Taxonomic discussion:— Microchilus dasilvae is similar to M. decorus ( Reichenbach 1873: 177) Smidt et al. (2021: 339) ( Table 1 ) due to the habit (small plants, up to 35 cm tall, and leaves up to about 6–7.5 cm in length) and floral display with stained sepals and mesochile with acute lateral lobes. It can be distinguished by the yellow (vs. white) mesochile and the broad-oval epichile about the same width as mesochile (vs. oblanceolate to narrow elliptical, proportionately narrower than mesochile). The complete illustration of M. decorus can be consulted in Sprunger et al. (1996: t. 136), as Physurus bicolor Barbosa Rodrigues (1882: 290) .

Additionally, M. dasilvae is similar to M. metallescens ( Barbosa Rodrigues 1882: 291) Smidt et al. (2021: 342) ( Table 1 ) due to the habit and floral display with stained sepals and white lip with yellow mesochile. It can be distinguished from this one by the narrow-elliptical and sub-falcated petals, slightly asymmetrical (vs. ovate and symmetrical); lip with mesochile with acute lateral lobes (vs. rounded); broad-ovate epichile with apiculate and obtuse apex (vs. oblong, non-apiculate obtuse apex); sepals with bilinear central longitudinal macula (vs. longitudinally trilinear macula). The complete illustration of M. metallescens can be consulted in Sprunger et al. (1996: 135) and Engels et al. (2016: 940).

Figures

FIGURE 1. Microchilus dasilvae.—A. Habit. B. Flower bract. C. Trichome of inflorescence. D-E. Flowers. D. Lateral view. E. Frontal view. F. Dorsal sepal. G. Petal. H. Lateral sepal. I-J. Lip. I. Flattened. J. Lateral view. K. Detail of the apex of the lateral lobe. L-N. Column. L. Dorsal view. M. Ventral view. N. Detail of the rostellum remain. O. Pollinarium. Drawing by Engels from M.E.Engels 9306.

FIGURE 2. Microchilus dasilvae—A. Habit. B–C. Leaf blade. B.Adaxial surface. C. Abaxial surface. D. Inflorescence. E–F. Flowers. E. Frontal view. F. Lateral view. Photos by Engels from M.E.Engels 9306.