Diagnosis. Thallus with slightly inflated branches holding low tubercles, trunk blackened below first ramification, cortex surface pruinose, soralia plane, circular with a thin cortical rim at maturity, medulla dense, with salazinic acid.
Type: Ecuador. Galápagos, Isla Santa Cruz, W of the dirt road along the quarry, 0°37.0'0.4''S, 90°22.0'1.3''W, 594 m alt., transition zone; open area along dirt road with herbaceous vegetation and scattered Bursera graveolens trees, on twigs of Bursera graveolens, 7-Aug-2008, Bungartz 8117 [holotype in CDS (40763)]. %C/M/A: 11.5/22/34.5. Chemistry: usnic and salazinic acid.
Etymology. Named for its superficial similarity to U. complecta.
Description.Thallus erect-shrubby to sub-pendulous, flaccid, with a soft touch; ramifications ±anisotomic-dichotomous; trunk usually black on the first mm, rarely pigmentation absent, brownish or slightly extending above first ramification, with few annular cracks often visible along trunk and basal branches; branches ±irregular, slightly to strongly inflated on basal branches, terminal branches often thin and sinuous; lateral branches not to distinctly constricted at ramification; maculae sometimes visible on basal branches, faint and whitish; foveoles absent; pseudocyphellae absent; papillae absent (see tubercles); tubercles usually abundantly distributed on basal and secondary branches, low and hemispherical, sometimes slightly elongated especially close to the base, often eroded at the tip (whitish); fibrils slender, scattered on branches; fibercles absent; soralia developing on the cortex of terminal branches, remaining plane, at young stage minute to slightly elongated with an irregular outline, at maturity becoming circular with a thin cortical rim; isidiomorphs short, scarce to abundant; cortex pruinose, opaque, soft to section, moderately thick, (7.5 –)9 –11.5(–13.5 %); medulla dense (hyphae visible individually), (13.5 –)22–28.5(–33 %); axis white, sometimes slightly pinkish, (19.5 –)23 –34.5(– 45.5 %), with an A/M-ratio of 0.75−1.5; apothecia and pycnidia not observed.
Chemistry. Medulla with salazinic acid [P+ yellow, K+ yellow turning deep red, C–, KC–].
Ecology and distribution. Presumably endemic to the Galapagos. A common species in the archipelago, abundant in the humid and upper transition zone, one specimen also from the high altitude dry zone; typically in open, often disturbed habitats (farmland areas, trees and fencepost along pastures), but inside the National Park also among native vegetation (remnants of Zanthoxylum woodland, Psidium galapageium woodland, Scalesia forests, and Miconia shrubland).
Notes.Usnea subcomplecta is distinguished by a flaccid thallus with barely to distinctly inflated branches, covered by low tubercles. The species has a blackish base below the first ramification, it has plane, circular soralia that, at maturity, remain delimited by a thin cortical rim. Its branches have a distinctly pruinose surface, an opaque cortex (i.e., mat in section), and a dense medulla (A/M-ratio < 1.5).
In the Galapagos specimens have branches that are usually distinctly inflated and thus slightly constricted at their ramification. However, a few specimens have branches that are barely inflated and do not appear constricted at their base. This is especially the case for compact morphotypes that most likely represent juvenile exemplars. The basal branches of these specimens are sometimes less abundantly tuberculate and the material can then best be identified because of its pruinose cortex. Soralia of U. subcomplecta generally remain plane and never become capitate or stipitate (as for example in U. complecta). Among the collections soralia nevertheless vary considerably in size and shape; a variation apparently correlated with overall thallus development: well developed thalli exhibit large, circular soralia delimitated by a thin cortical rim; less often the soralia remain minute or become only slightly elongate, they are then sparsely distributed and confined mainly to the terminal branches; rarely soralia are almost absent, or they can be crowded and aggregated in irregular clusters.