Parmotrema perlatum (Huds.) M.Choisy
Lichen perlatus Huds., Fl. angl.: 448 (1762).
Thallus orbicular to spreading, loosely attached, 5-15 cm diam., corticolous or saxicolous. Lobes rounded, 8-15 mm wide, margins entire, often strongly sinuous, black, shining, ciliate, cilia rather sparse, 0.5-2 mm long. Upper surface pale greenish-grey or bluish-grey in damp habitats, to white or greyish-white in exposed habitats, smooth, matt, often wrinkled and usually cracked in older parts, submarginally sorediate. Soralia linear, soon eroding a large area and causing margins to become strongly revolute or capitate-hooded, soredia fine, powdery, white. Lower surface black and shining, with a conspicuous dark brown, naked marginal zone. Rhizines central, long, black, simple. Apothecia rare, pedicellate, to 6 mm diam., disc concave to ± plane, matt, pale brown to red-brown, imperforate, margins thick, inflexed, sorediate. Ascospores 25-28 × 16-18 µm. Pycnidia occasional, minute, black, punctiform, mainly marginal. Chemistry: Cortex K+ yellow; medulla K+ persistent yellow, C-, KC-, Pd+ pale orange. Atranorin and stictic acid.
N: North Auckland to Wellington. S: Nelson to Southland. St: A: C: Very widely distributed and probably the most common species of Parmotrema in New Zealand. Primarily corticolous it will also colonise rocks, especially in coastal habitats.
Cosmopolitan
P. perlatum appears to be one of the most effectively dispersed lichens in New Zealand being an early and common coloniser of sawn and decorticated wood and, together with species of Ramalina and Usnea, soon colonises fenceposts and telegraph poles. It rarely occurs as an epiphyte of standing forest trees but is commonly encountered on the bark of Leptospermum and other shrubs on disturbed ground, as well as on introduced trees and shrubs in parks and gardens. The ease of its dispersal and rapidity of growth on decorticated wood substrates and its comparative rarity in undisturbed habitats, particularly in native forests, argue strongly for P. perlatum being a highly successful adventive lichen whose range has been greatly increased by man and his activities.
Related chemically to P. crinitum, it is distinguished from it by the presence of soredia and the lack of isidia. It is most commonly confused with P. reticulatum but this species has a different chemistry (medulla K+ yellow → red-salazinic acid) and is consistently strongly maculate or reticulate-cracked.
