Masdevallia rubileoixchelorum D. Gutiérrez

Pozo, Diego Gutiérrez Del, Jiménez, Marco M., Vélez-Abarca, Leisberth & Baquero, Luis E., 2022, A new Masdevallia (Orchidaceae: Pleurothallidinae) from the Ecuadorian Amazon foothills of the Llanganates mountains, Phytotaxa 552 (3), pp. 191-200 : 192-198

Masdevallia rubileoixchelorum D. Gutiérrez del Pozo, M.M. Jiménez & Vélez-Abarca, sp. nov. ( Figures. 1–4 )

Type: — ECUADOR. Napo: canton Arosemena Tola, Alto Piatúa Reserve of the CEIPA-UEA, 44 km north of Puyo along the road to Tena, 845 m above sea level, 24 Nov 2021, D. Gutiérrez del Pozo 145 (holotype: ECUAMZ!) .

Similar to M. aphanes from which it differs in the obconical ovary, with undulating ribs (vs. semiterete and verrucose), the yellow, striped with red-brown sepals (vs. dull yellowish-green, vaguely striped and diffusely spotted with brown, verrucose abaxially), the convex and subpandurate lip with decurved margins, the two ribbed, broad calli which extend close to the apex of the lip (vs. the three longitudinal calli, two undulating from the base disappearing towards the apex and one straight and extending from the apex towards the middle of the blade) and the column, with a hooded clinandrium and ventrally concave with winged margins (vs. semiterete).

Description:— Epiphytic up to 3 cm tall including the inflorescence, caespitose herb. Roots filiform, 0.7–0.9 mm in diameter. Ramicauls slender, shorter than the blade, 3–9 mm long, concealed by 2–3 tubular, loose, papyraceous, 0.7–2.1 mm long sheaths. Leaves erect, coriaceous, the blade elliptic to lanceolate, 10–21 × 3–4 mm, acute to subacute, minutely mucronate, attenuate to the petiole; petiole channeled, 2–8 mm long. Inflorescence a successive raceme, up to two flowers, borne by a more or less horizontal, filiform peduncle 3.6–4.4 cm long, borne close to the base of the ramicaul, enclosed by a tubular 2.5–3.0 mm bract, close the base; floral bract infundibuliform, 2.4–2.9 mm long. Pedicel terete, 3.6–4.3 mm long. Ovary obconical, glandulose, 2.0–2.2 × 1.6–1.8 mm, with undulating-dentate, membranaceous ribs. Sepals yellow, papillose adaxially, abaxially with three, red-brown carinae, and three reddishbrown to ruby-red stripes adaxially, microscopically serrulate at the margin; dorsal sepal ovate, 8.8–8.9 × 3.8 mm, 3-veined, the free portion triangular, acute, thickened; connate to the lateral sepals for 3 mm to form a broad, gaping sepaline cup; lateral sepals ovate, triangular, oblique, 8.5–8.7 × 9.4–9.5 mm, 3-veined, connate to the base for 2.5 mm, the apices acute. Petals white, unguiculate, spathulate, subacute, 2.9–3.5 × 1.9–2.0 cm, 2-veined, with three, minute, apical teeth, the central tooth larger than the lateral teeth, with a low callus along the lower margin, veins pale yellow. Lip yellow tinged with red-brown between the two ribbed, fleshy, longitudinal calli, turning ruby-red towards the apical half, convex, forming a deep slipper-like shape when observed abaxially, subpandurate in natural position, with revolute margins adaxially forming a skirt with slightly crenate margins, 4.3–4.4 × 1.7–1.8 mm, 3-veined, papillose, narrowing to the base, base emarginate, articulated to the column foot, the apex rounded; the disc with two broad, longitudinal fleshy, ribbed calli extending for three-fourths of the lip length, centrally with a deep channel at the first half of the lip becoming shallower towards the inflated apex. Column yellowish green, whitish below the middle, with two reddish-brown stripes ventrally, 3.4–4.3 × 1.5 mm, smooth, ventrally concave with winged margins; column foot 2.4 mm long, 2–keeled centrally, rostellum bilobulate, clinandrium cucullate. Anther white tinged with yellow, ventral, 0.9 mm long; stigma elliptic. Pollinia 2, yellow, obovoid, 0.7 mm long.

Etymology:— The name of this species is dedicated to the children of the first author and discoverer of the new taxa: Alexandra Rubí, Leonardo Felipe and María Ixchel. The name also reflects the colors of the perianth: Rubi to ruby-red in the lip, Leo (which is related to the solar symbol) could evoke the dominant yellow of the sepals, and Ixchel, venerated as the goddess of the Moon by the Mayan culture, would remind us the white colored petals.

Distribution and habitat:— The holotype of Masdevallia rubileoixchelorum was found at the Alto Piatúa Reserve of the CEIPA-UEA (research center of the Universidad Estatal Amazónica), which is located on the eastern flank of the Llanganates mountains, at the confluence of the Anzu and Piatúa Rivers in Napo province of northeastern Ecuador. Three specimens were found on fallen tree branches on a river terrace in wet premontane forest remnants along the Piatúa River at 845 m elevation. The forest soil is sandy and is derived from granite bedrock upriver, mixed with clay soils. The tree species Otoba parvifolia Markgraf (1926: 964) Gentry (1979: 417) (Myristicaceae) , Vochysia braceliniae Standley : (1940: 149) and Iriartea deltoidea Ruíz & Pavón (1798: 298) (Arecaceae) are common in this area. The specimens found in the area were found growing together with other small orchids such as Dryadella cuspidata Luer & Hirtz (1999: 160) , Pleurothallis scabrilinguis Lindley (1836: 354) , Stelis sp. , Octomeria mocoana Schlechter (1924: 59) and Octomeria subcallosa Forster (2012: 487) .

Taxonomic Discussion:— The ovary with undulate-dentate ribs which are almost keeled, the abaxially deep sandal-shaped lip with the inflated apex of the calli and the bilobulate rostellum of Masdevallia rubileoixchelorum ( Figure 2 ), are unique features within Masdevallia ; the first character is reminiscent of the ovaries of Dracula subsect. Costatae ( Luer 1991: 10), the bilobulate rostellum is observed as remnant in different clades of the subtribe Oncidiinae ( Kolanowska & Szlachetko 2014, Szlachetko & Kolanowska 2015, Szlachetko & Kolanowska 2016, Szlachetko et al. 2017, Szlachetko et al. 2019).

Masdevallia rubileoixchelorum belongs to a group of species within Masdevallia subg. Masdevallia sect. Aphanes characterized by having triangular, acute to subacute lateral sepals, not contracted into tails (Luer 2000). It is distinguished from the most similar species M. aphanes ( Figure 3B ) by the descending-horizontal (vs. erect) inflorescences, the smaller flowers (6.9 × 10.6 vs. 8.7 × 14.3 mm) with the white petals (vs. yellow-green, spotted with dark purple) and the lip convex, subpandurate, apically acute, narrowed to the base (vs. flattened down, spathulate, obtuse to rounded, unguiculate at the base). Also, it is similar to Masdevallia trifurcata Luer (1994: 252) ( Figure 3C ) by the horizontal inflorescences, the ovary with undulating ribs and the yellow color of the sepals but is distinguished by the smaller size of the plants (2.5 cm vs. 6.3 cm), the striped (vs. finely dotted) flowers with triangular free parts of the sepals (vs. narrowly triangular), the white, elliptical (vs. yellow, oblong) petals and the not clawed, subpandurate, acute (vs. unguiculate, oblong, obtuse) lip and the concave, laterally winged (vs. semiterete) column.

In addition, it is similar to Masdevallia mentosa Luer (1978c: 212) ( Figure 3D ) by the flower morphology, but is distinguished by the smaller plants (2.5 cm vs. 9.1 cm), the descending-horizontal, filiform peduncles (vs. suberect, slightly triquetrous to the apex), the ovary with undulate ribs (vs. slightly costate), the intense yellow, striped, glabrous sepals (vs. translucent, with few markings on the margins, sparsely short pubescent below the middle), the elliptic, white (vs. narrowly oblong with a rounded process, yellow-green) petals, the panduriform, acute (vs. oblong-ligulate, rounded) proportionally shorter to the sepals lip and the winged along the margins column (vs. winged above the middle).

All four taxa are located in the eastern slopes of the Andes, Masdevallia rubileoixchelorum and M. mentosa are two lowland species endemic to the rainforests of the Napo and Pastaza provinces in central eastern Ecuador around 600–800 m; while, M. aphanes is reported from localities in northeastern Peru and northeastern Ecuador (Carchi province), at elevations over 1700 m. Also, M. trifurcata has been found in the Cordillera del Cóndor mountains in the province of Zamora-Chinchipe, southeastern Ecuador, at elevations around 1500 m (Luer 2000) ( Figure 4 ).

Conservation status: — This new species is known only from the type collection made in the Alto Piatúa Reserve; however, we have seen a photograph of it posted on the Facebook page of a European orchid enthusiast, evidently from a plant that was exported illegally. Numerous miniature orchids are frequently collected for their diversity in flower and leaf ornamentation, including several native ones from Ecuador, such as the recently described Trisetella pachycaudata (2021: 272) ( Baquero & Mogrovejo 2021). The export of the parental material of these species could be facilitated and unfortunately more difficult, and all but impossible to monitor by failing to provide accurate reporting to CITES databases ( Yeager et al. 2020).

Data from PROAmazonía (2021) show that primary forests of Carlos Julio Arosemena Tola canton in the Ecuadorian province of Napo are under severe pressure for overuse; 75% of the territory is native forest, while 23.53% is used for agricultural activities and timber extraction. These threats are the main cause of deforestation, leading to the transformation and loss of native vegetation.

Masdevallia rubileoixchelorum is known from a single population within the forests of the Alto Piatúa Reserve in the canton Carlos Julio Arosemena Tola: The collection site is within the Research Center of the Universidad Estatal Amazónica and although were used in the past as a source of timber, actually is not under extreme threat. Under the IUCN criteria ( IUCN 2022), this species is considered Data Deficient, due to the recent discovery and the need for more research effort.

Figures

FIGURE 1. Line drawing of Masdevallia rubileoixchelorum. A. Habit. B. Flower. C. Dissected perianth showing the extended lip. D. Ovary, column and lip in lateral view. E. Lip, in adaxial, lateral and abaxial view. F. Column, ventral view. G. Anther cap and pollinarium. By L. Vélez-Abarca based on the plant that served as type.

FIGURE 2. Masdevallia rubileoixchelorum. A. Habit. B. Flower. C. Dissected perianth. D. Ovary, column and lip in lateral view. E. Lip, in adaxial, lateral and abaxial view. F. Column, ventral view. G. Anther cap and pollinarium. Plate by L. Vélez-Abarca based on the plant that served as type.

FIGURE 3. Details of the flowers. A. Masdevallia rubileoixchelorum. B. Masdevallia aphanes C. Masdevallia trifurcata D. Masdevallia mentosa. A. Photograph by M.M. Jiménez. B–D. Photographs by L. Grobler.

FIGURE 4. Distribution map of Masdevallia rubileoixchelorum and related species. ● Masdevallia rubileoixchelorum. ▲ Masdevallia aphanes. éMasdevallia trifurcata. ■ Masdevallia mentosa. Prepared by Henry X. Garzón.