Dendrochilum hampelii Sulistyo, Gravend., R.Boos & Cootes, 2015

Sulistyo, Bobby P., Boos, Ronny, Cootes, James E. & Gravendeel, Barbara, 2015, Dendrochilum hampelii (Coelogyninae, Epidendroideae, Orchidaceae) traded as ' Big Pink' is a new species, not a hybrid: evidence from nrITS, mat K and ycf 1 sequence data, PhytoKeys 56, pp. 83-97 : 89-90

Dendrochilum hampelii Sulistyo, Gravend., R.Boos & Cootes sp. nov. Figs 3 , 4

Type.

Sine loco et anno, Perry 490 (holotype L!).

Diagnosis.

This new species is similar to Dendrochilum propinquum Ames, but is distinguished by its larger flowers with petals proportionally broader (1.4-1.5 ×) than the sepals, a broadly cordate labellum (6.8-8.0 × 7.2-7.6 m) and acute stelidia.

Medium-sized, tufted epiphytic herb. Roots appearing from the rhizome, ca. 2.7 mm in diameter. Pseudobulbs tightly clustered on a short rhizome, fusiform, 3.5-5.0 cm long, 0.5-1.4 cm in diameter, longitudinally striated when dry, 1-leaved, initially covered by ca. 3 imperfectly to nearly perfectly tubular, rounded to acute cataphylls that soon disintegrate into persistent fibers. Leaves convolute, dorsiventrally flattened, petiolate; petiole channeled, 3.0-4.5 cm long; lamina (ob)lanceolate, obtuse, 13.0-20.0 × 3.7-5 cm, subcoriaceous, with 7-8 distinct (and many indistinct) nerves. Inflorescence synanthous, racemose; peduncle suberect, arched, slender, somewhat flattened, 18.0-21.2 cm long, sparsely and finely setose; rachis pendent with distichously alternating flowers (but the rachis axis twisted so as to produce a cylindrical inflorescence), many-flowered with internodes of 3-7 mm, somewhat furrowed, 20.0-27.5 cm long, sparsely and finely setose, basally with 1 appressed non-floriferous bract; flowering starting from the proximal part of the rachis. Floral bracts glumaceous, broadly lanceolate to (ovate-)oblong when flattened, obtuse to acute, 4.0-9.5 × 2.2-4.3 mm, entire, 9 - to 19-nerved from the base, finely setose on the dorsal side. Flowers non-resupinate, pinkish salmon-coloured (Fig. 4A-B ) or pale yellow (Fig. 4C ) with yellow anther. Sepals recurved with revolute margins, entire, obtuse to rounded, minutely mucronate, glabrous, 3- to 5-veined from the base; dorsal sepal lanceolate-oblong, 8.7-11.0 × 3.5-3.7 mm when flattened; lateral sepals ovate-oblong, slightly oblique, 8.1-10.0 × 3.7-4.0 mm when flattened. Petals recurved with flat margins, broadly (ovate-)elliptic, often with a subbasal fold in either side, rounded to acute, 8.4-11.1 × 5.4-5.7 mm, 1.4-1.5 times as wide as the sepals, entire, glabrous, 3- to 5-veined from the base. Labellum firmly attached, sessile, describing a right to obtuse angle to the column, flat, broadly cordate with entire margins, acute to short-acuminate, 6.8-8.0 × 7.2-7.6 mm, without ornaments, glabrous and smooth, 5- to 7-veined from the base. Column suberect, straight, semiterete, 1.7-2.1 mm long, smooth, distally prolonged into a truncate to obscurely 3-lobed wing that distinctly exceeds the anther; stelidia appearing from the distal part of column proper, erect, falcately triangular-oblong, acute, subequal to the apical wing; anther circular to transversely elliptic in upper view, rounded in front, lobed at the back, with a small wart on top; pollinia 4, ellipsoid, devoid of caudicles; rostellum slightly protruding, flat, semicircular; fertile stigma part crescent-shaped, concave. Ovary (including pedicel) subterete, slightly longitudinally furrowed, twisted through 180°, distally incurved, 3.8-4.5 mm long, glabrous. Fruit not seen.

Additional material examined.

PHILIPPINES? Sine loco et anno, sine coll./cult. Hort. bot. Leiden 20130654 (L! [spirit no. WAG0116920]).

Etymology.

The specific epiphet honours Georg Hampel, who was one of the first to provide us with study material of the newly described species.

Distribution and ecology.

The species occurs in the wild in the Philippines in the northern provinces of Bukidnon and Misamis Oriental on the island of Mindanao (Fig. 4C ). It grows as an epiphyte at elevations approximately 1,200 m above sea level among mosses on the trunks and branches of trees. Fresh flowers of plants observed in the wild were pale yellow whereas fresh flowers of the cultivated plants studied were pinkish salmon-coloured. We do not consider this reason to describe them as a different variety or forma as color dimorphism is known to occur in other Coelogyninae as well ( Gravendeel 2000).

Reproductive biology.

The live plant in Leiden flowered in mid-December. Attempts to pollinate flowers of Dendrochilum hampelii were made using pollinia from the same flower and pollinia from a different flower in the same inflorescence. None of these efforts led to fruit formation. This indicates that Dendrochilum hampelii is probably self-incompatible, as previously demonstrated for Dendrochilum longibracteatum Pfitzer ( Pedersen 1995), although it should be noted that experimental pollination was severely challenged by the small size of the stigmatic cavity.

Conservation status.

Although the species occurs in cultivation we as yet know very little about the distribution and abundance of Dendrochilum hampelii in the wild. As such, we recommend the species to be considered for the Data Deficient category of the IUCN Red List of Threatened Species ( IUCN 2012).

Figures

Figure 3. Dendrochilum hampelii: a habit b floral bract c flower d flower (sepals and petals removed) e dorsal sepal f petal g lateral sepal h labellum i column, front view j anther k pollinia. Drawing by Esmee Winkel based on Hort. bot. Leiden 20130654 (L! [spirit no. WAG 0116920]).

Figure 4. Dendrochilum hampelii: A portion of inflorescence of cultivated pinkish salmon-coloured form B habit. Photographs by Lubbert Westra of Hort. bot. Leiden 20130654 (L! [spirit no. WAG 0116920]) C portion of inflorescence of pale yellow-coloured form of a plant growing in the wild in the Philippines in the Misamis Oriental province of the island of Mindanao. Photograph by James Cootes.