Dominican Parmotrema Lichen

Parmelia dominicana

Parmelia dominicana Vainio, 1896, p. 32.

P. perlata var. flavogranulosa Vainio, 1915, p. 13. [Type collection: Mt. Stewart, St. Croix, Raunkiaer 433 (TUR,lectotype; C, isotype).]

P. capitulifera Zahlbruckner in Magnusson, 1942, p. 9. [Type collection: Punaluu, Oahu, Hawaii, Rock 176 (W, lectotype; BPI, isotype).]

TYPE COLLECTION.—Crater Souffrière, Dominica, Elliott 114 (TUR, holotype).

DESCRIPTION.—Thallus loosely adnate, up to 15 cm in diameter, mineral gray with a yellowish tinge; lobes broad and rotund, 8–12 mm wide; sorediate along the margins, soralia orbicular to linear, the soredia powdery, distinctly yellowish, cilia lacking; lower surface black and sparsely rhizinate, naked and brown in a zone along the margin. Apothecia rare, 3–5 mm in diameter; spores 5–7×16–18μ.

CHEMISTRY.—Cortex K+ yellow (atranorin); medulla K– or faint yellow, C–, KC–, P+ red orange (protocetraric acid). Usnic acid is present in the soredia.

WORLD DISTRIBUTION AND HABITATS.—Tropical America, Angola, Congo, Rhodesia, Hawaii; on trees at lower elevations (sea level to 1,200 m).

Parmelia dominicana is a distinct and easily recognized species on Dominica and over most of its range. In some regions, however, there is intergradation with P. dilatata Vainio, which in general has more irregular sparse soralia, mostly on short marginal lobules, and white soredia, although traces of usnic acid may be present in the upper cortex. Both species contain protocetraric acid.

It was evident that Vainio was confused on the identity of his new species. The holotype is corticolous and has the distinct yellowish soralia so characteristic of P. dominicana. In his later publication, however, he identified identical material from Prince Rupert as P. perlata var. flavogranulosa and called several rock-inhabiting specimens from St. Thomas P. dominicana. This latter material on rock is P. mordenii (see under the species).

Parmelia dominicana occurs mostly on palm trees along the west coast in Dominica and is the most common lichen in the Roseau Botanical Garden. It does not occur in the rain forest.

SPECIMENS EXAMINED.—Prince Rupert, Elliott 1310 (TUR). Hale collections: 1 (35674), 2 (35632A, 35640), 6 (35785), 7 (35792), and 8 (35756A). Roseau Botanical Garden, Evans 57 (NY) and 59 (US).