Parmotrema peralbidum (Hale) Hale

Parmelia peralbida

Parmelia peralbida Hale, 1965, p. 257.

TYPE COLLECTION.—Jamaica, Hart 124 (FH-Tayl, holotype; BM, isotype).

DESCRIPTION.—Thallus loosely attached, 5–10 cm in diameter; lobes broad and rotund, 8–12 mm wide; upper surface plane, sparsely to moderately isidiate, the isidia thin, cylindrical; lower surface black, sparsely rhizinate toward the center, the outer margin naked and brown. Apothecia rare (not seen in Dominica), up to 4 mm in diameter; spores simple, 5–7×8–10μ.

CHEMISTRY.—Cortex K+ yellow (atranorin); medulla K–, C–, KC–, P+ orange red (protocetraric acid).

WORLD DISTRIBUTION AND HABITATS:—Mexico, Honduras, and the West Indies; on hardwoods (mossy forest) at higher elevations (600–1,500 m).

This rare lichen could be mistaken for P. tinctorum Nylander, a lowland species with coarser subgranular isidia and different chemistry (P–, lecanoric acid). The collections from Dominica definitely establish P. peralbida as a high elevation rain forest or mossy forest lichen, thus ecologically as well as chemically distinct from P. tinctorum.

SPECIMENS EXAMINED.—Hale collections: 20 (35454) and 21 (35353).