Aerides obyrneana Metusala, 2024
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publication ID |
https://doi.org/ 10.24823/EJB.2024.2001 |
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persistent identifier |
https://treatment.plazi.org/id/03E987BA-FFF3-5251-752E-FE475487A3C6 |
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treatment provided by |
Felipe |
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scientific name |
Aerides obyrneana Metusala |
| status |
sp. nov. |
Aerides obyrneana Metusala , sp. nov.
Aerides obyrneana is morphologically similar to A. upcmae Motes et al. but differs in having a broadly flabellate mid-lobe (vs elliptic ovate mid-lobe), mid-lobes deeply incised forming 4 unequally lobules (vs simple with bilobed apex), a low median callus that extends from the spur aperture to the centre of the mid-lobe (vs shallowly channelled at the posterior base), and a spur with an erect subquadrangular lower callus (vs an erect long oblong lower callus). – Type: Indonesia, Sulawesi Island, Gorontalo Province, 300–510 m, RIO 62 (holotype BO). Figures 1 View Figure 1 , 2 View Figure 2 .
Epiphytic monopodial herb, plant small to medium size for genus (leafy stem 10–16 cm long), suberect to pendulous. Roots few from stem base, occasionally from nodes along stem, 0.4 cm in diameter, can reach 60 cm long, frequently branching, white. Stem stout, cylindrical, internodes 0.8–1.5 cm long, covered by imbricating basal leaf sheaths, stem length up to 15 cm long, leafy along much of the length. Leaves strap-shaped, 4–13 × 1.2–2 cm, green, slightly stiff and leathery, keeled underneath, rather waxy on adaxial surface, glabrous; apex obliquely and unequally bilobed, lobules obtuse, keel protruding in sinus as a small point. Inflorescences descending, 10–17 cm long, with 5–7 flowers arranged radially on a 5–8 cm rachis, most flowers open at same time; peduncle 5–9
× 2–2.5 mm, cylindrical, glabrous, green, with broadly triangular bract, obtuse to acute, 3–4 mm wide at base × 2–2.5 mm long; floral bract 3–4 × 5–6 mm at base, triangular, obtuse to acute, brown reddish; pedicel-with-ovary cylindrical, 1.3 cm long. Flowers 2.5–2.6 × 2.4–2.5 cm, opening fully, sepals and petals waxy, stiff and shiny; pedicel (with ovary) pinkish white, graduating to darker pinkish purple towards the apex; sepals and petals white with pink-purple blotch near the apex and suffused pink-purple longitudinally in the median, pink-purple more pronounced on the sepals; lip side lobes greenish yellow to yellow, often with purple transverse streaks at base; mid-lobe yellow turning paler towards apex, with purple transverse streaks at base and pink-purple median markings, apex speckled pink-purple; callus white with pink-purple specks on the ridge; spur greenish yellow at base and reddish brown at the tip; column and foot white; anther cap white, turning to pale brown with age; pollinia yellow. Dorsal sepal suberect, 1–1.1 × 0.7–0.8 cm, unequally elliptic to ovate, obtuse, margins minutely erose, slightly concave. Petals horizontally widespread, 1.1–1.2 × 0.7–0.8 cm, unequally obovate, obtuse, margins minutely erose. Lateral sepals horizontally widespread, often slightly deflexed, 1–1.1 × 0.9–1 cm, broadly unequally elliptic, obtuse, apiculate, margins minutely erose. Lip base attached only to column-foot apex, porrect, 16–18 mm long (with spur), 3-lobed and spurred from the base; when flat 25–26 mm wide across the middle; side lobes porrect and slightly spreading, 11 mm long, from a thickened narrow base somewhat falcate, cuneate to oblong, apex truncate to broadly rounded, erose to denticulate; mid-lobe porrect, rising at the sides, broadly flabellate from a narrow thickened base (claw), 13–15 (including claw) × 14–18 mm, the front broadly rounded and deeply incised forming 4 unequal lobules, front margins dentate; 5–7.5 mm long, low median callus extending from spur aperture to centre of the mid-lobe, callus bilobed at the spur entrance; the lobules projecting backwards into the aperture; spur briefly descending then abruptly incurved through 90–100°, in total 9.5–10 mm long, 6 mm wide at base, cylindroconical, tapering to a narrow obtuse apex, thick-walled, the backwall opposite the mid-lobe internally with an erect quadrangular lower callus that projects halfway across the aperture. Column porrect, 4.5–5 mm long, slender, apex blunt with a large prominent triangular rostellum; foot descending an obtuse angle, bent in the middle, 10–11 × 3–4.5 mm, lateral margins raised and keel-like, foot apex bears a nectary in a depression. Anther cap cucullate, prominently beaked, 4.5–5 mm. Pollinia 2, subglobose to subovoid, about 1–1.3 mm high. Stipe and viscidium not seen.
Description based on living plant and spirit material.
Distribution. Indonesia, Sulawesi Island, Gorontalo Province. Exact locality withheld to protect population from illegal orchid collectors.
Habitat and ecology. Growing as an epiphytic under the shade of old trees in semi-open hilly area. Flowering so far recorded only between April and May (eX situ in Purwodadi Botanic Garden, East Java, 300 m). This species has a narrow leaf shape with a thick waxy cuticle layer on the leaf adaxial surface, which in tropical epiphytic orchids is usually related to adaptation to low humidity, hot temperature, relatively high light–intensity environments, and long drought period ( Al Farishy et al., 2017; Metusala et al., 2017; Metusala, 2019a; Ishmah et al., 2021; Suffan et al., 2021; Metusala & Al Farishy, 2022).
Etymology. The specific epithet honours the late Peter O’Byrne, a Southeast Asian orchid specialist who kindly taught the author during his early career as an Indonesian taxonomist.
Proposed IUCN conservation category. Aerides obyrneana is so far known only from a single locality in Gorontalo province. The bright attractive colour and very unusual lip shape compared with that of other Indonesian Aerides make this species vulnerable to over-collection by commercial collectors and orchid enthusiasts. Intensive collection to meet the high demand from collectors often has a great negative impact on the sustainability of orchid population in their habitat (Metusala, 2017). The quality of natural habitat is also declining, due to conversion of forest to plantations. The species is thus provisionally assessed as Critically Endangered B2ab (i,ii,iii,v) until more data on its current population become available.
Notes. From the large lip mid-lobe compared with its side lobe, and its mid-lobe being perpendicular to the side lobes, Aerides obyrneana is most similar to species in Aerides sect. Falcata , a section mostly found in mainland Southeast Asia ( Averyanov et al., 2019; Motes et al., 2020). A new species of this group, Aerides upcmae , published in 2020 from Mindanao Island in the Philippines ( Motes et al., 2020), extended the distribution of the section east. The discovery of Aerides obyrneana in the northern part of Sulawesi Island extends sect. Falcata south, and it is the only member of this section in Indonesia. It is clear that Aerides obyrneana and A. upcmae show intermediate characters between sect. Falcata and sect. Aerides , especially in their spur shape. These sections may ultimately be merged, or a new section may be created to accommodate both species; however, until a more detailed study of the sectional classification in the genus is carried out, Aerides obyrneana is placed in sect. Falcata.
Aerides obyrneana is morphologically similar to A. upcmae and A. houlletiana (Table).
The flowers of Aerides obyrneana are similar to those of A. houlletiana but differ in having a broadly flabellate lip mid-lobe, unequally oblong lip side lobes that are broader towards the truncate apex with erose apical margins, a low median keel that extends from spur aperture to centre of the lip mid-lobe, a curved spur, and a prominent bilobed callus that is raised on the front wall under the spur aperture. By contrast, Aerides houlletiana has a subrectangular to broadly ovate lip mid-lobe, unequally elliptic lip side lobes with obtuse to rounded apex and entire apical margins, two distant longitudinal keels that converge in the base area of the lip mid-lobe, and a straight spur, and is without a prominent callus on the front wall under the spur aperture ( Figure 3 View Figure 3 ).
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