Xanthoparmelia Lichen

Parmelia subramigera

Parmelia subramigera Gyelnik, 1931, p. 281. [For full synonymy see Hale, 1964, p. 471.]

TYPE COLLECTION.—Rainbow Fall, Hawaii, Faurie 856 (BP, holotype; BM, isotype).

DESCRIPTION.—Thallus adnate on rocks, 4–10 cm broad, greenish yellow; lobes linear-elongate, 2–3 mm wide; upper surface moderately isidiate, the isidia cylindrical, simple; lower surface pale brown, moderately rhizinate, the rhizines brown, simple. Apothecia rare (not seen in Dominica.)

CHEMISTRY.—Cortex K– (usnic acid); medulla K–, C–, KC–, P+ red (fumarprotocetraric acid and “sublimbatic” acid). TLC analyses have shown that “sublimbatic” acid is a constant accessory substance except in Japan where it is lacking. This unknown also occurs with fumarprotocetraric acid in other Xanthoparmeliae (P. hypomelaena Hale, P. subconspersa Nylander, and P. subfuscescens Nylander) and in subgenus Parmelia section Relicinae (P. ramossissima Kurokawa and P. sublimbata Nylander). It is recognized on TLC plates as a spot just below fumarprotocetraric in n-butanol-acetone.

Parmelia subramigera is the commonest, sometimes the only member of subgenus Xanthoparmelia occurring in tropical regions. On the northern border of its range it intermingles with a series of chemical populations that share essentially the same morphology: P. plittii Gyelnik (containing stictic and norstictic acids), P. mexicana Gyelnik (salacinic acid), P. kurokawae Hale (psoromic acid), and P. dierythra Hale (norstictic acid). These are discussed in Hale, 1964, p. 470.

In Dominica, P. subramigera is rather common on lava rocks all along the west coast. There are not many herbarium specimens because the thallus is difficult to collect from the rocks.

SPECIMENS EXAMINED.—Hale collection: 4 (35–778). Rodneys Rock, Robinson s.n. (US).