Psilochilus dressleri Kolan., 2014

Kolanowska, Marta, 2014, Psilochilus dressleri (Orchidaceae), a new species from the Darién Gap, Panama, Phytotaxa 175 (1), pp. 55-58 : 55-56

Psilochilus dressleri Kolan. , sp. nov. ( Fig. 1 )

Species similar to P. macrophyllus (Lindl.) Ames , distinguished by distinctly clawed lip with prominent lateral lobes that extend up to two-thirds of the mid-lobe and relatively small mid-lobe suborbicular in outline.

Type:— PANAMA. Darién: Ridge north of Cerro Pirre , 1050–1200 m, 12 July 1977. R. L . Dressler 5663 (holotype FLAS!) .

Plant ca. 36 cm tall, leafy throughout. Leaves 6–7 × 2.9–3.4 cm wide, ovate, subacute; petiole less than 0.5 cm long. Inflorescence about 2.5 cm long, few-flowered. Floral bracts up to 10 mm long. Ovary 16 mm long. Flowers rather inconspicuous, petals and sepals pale green, lip cream with purple mark. Dorsal sepal 19 × 2 mm, concave, oblonglanceolate, obtuse, 3-veined. Lateral sepal 18 × 2 mm, falcate, linear, subacute, 3-veined. Petals 17 × 1.5 mm, slightly falcate, linear, subobtuse, 3-veined. Lip 14 mm long, 6 mm wide across the lateral lobes; claw about 6 mm long; lateral lobes 7.5 × 2.5 mm, large, obliquely ovate-falcate, obtuse, extending to two-thirds of the mid-lobe, internal parts overlapping the mid-lobe; isthmus deep; mid-lobe 4 mm long and about the same width, suborbicular, obtuse, margins entire; disc with 3 thickened veins. Gynostemium ca. 16 mm long.

Distribution and ecology: —Known so far exclusively from the Darién Gap, where it was found growing in wet forest at the altitude of about 1,050 –1,200 m. Type material with flowers in July.

Etymology: —Dedicated to Robert L. Dressler, eminent orchidologist and the collector of the type specimen.

Taxonomic notes: — This species resembles Psilochilus macrophyllus ( Lindley 1858: 335) Ames (1922: 45) with relation to their subsessile leaves but it differs by the prominent, large lateral lobes of the lip that extends to twothirds of the mid-lobe and relatively small mid-lobe which is almost twice shorter than lateral lobes and suborbicular in outline, with entire margins. Moreover, in P. macrophyllus the lip is subequal in length to the sepals (vs much shorter than sepals in P. dressleri ) and it is only shortly clawed (vs. claw prominent). The differences in the lip form between the two species are presented in Fig. 2 . From another Panamanian representative of the genus, P. physurifolius ( Reichenbach 1859: 324) Løjtnant (1977: 168) , the new species is easily distinguished by the subsessile leaves (vs. leaves distinctly petiolate) and the prominent lateral lobes of the lip (vs. short lateral lobes).

Figures

FIGURE 1. Psilochilus dressleri. Dissected perianth.A. habit. Scale bar = 5 cm. B. Dorsal sepal. C. petal. D. Lateral sepal. E. Lip. Scale bars = 5 mm. Drawn from the holotype.

FIGURE 2. Comparison of the lip shape of Psilochilus dressleri (A. Drawn from the holotype) and P. macrophyllus (B, redrawn by A. Król from Ames & Correll 1952).