Diagnosis. Thallus erect-shrubby, non-inflated branches with abundant tubercles, base blackish on first mm, soralia plane, circular to elongated, remaining well-delimited by a thin cortical rim, even when aggregating, cortex mat, medulla very thin, axis very thick, with salazinic acid.
Type: Ecuador. Galápagos, Isla San Cristóbal, along trail to Ochoa, along the northern border of the National Park, 0°53.0'39.3''S, 89.0°33.0'18.8''W, 315 m alt., humid zone, vegetation with Citrus sinensis, Psidium guajava and Zanthoxylum fagara, slope 10° S, on branches of a fallen tree, 24-Aug-2008, Truong 1427 [holotype in CDS (39738); isotype in G]. %C/M/A: 8.5/4/75. Chemistry: usnic and salazinic acid.
Etymology. Named in appreciation of Patricia Jaramillo, the herbarium curator of the Charles Darwin Research station, for her friendship and continued support of the Galapagos Lichen Inventory.
Description.Thallus erect-shrubby to subpendulous; ramifications ±isotomic-dichotomous; trunk blackish to brownish on the first mm (below first ramification), often with thin annular cracks extending on basal branches; branches cylindrical to irregular in diameter, not inflated; lateral branches not constricted at ramification; maculae absent; pseudocyphellae absent; papillae absent to sparse (see tubercles); tubercles typically abundant, hemispherical, later eroded at the tip; fibrils slender, scattered to abundantly distributed on branches; fibercles absent; soralia developing on the cortex of secondary and terminal branches, plane, circular to elongated, remaining well-delimited by a thin cortical rim even when crowded, enlarging almost to the branch diameter and/or becoming slightly capitate at maturity; isidiomorphs few to abundant, short; cortex epruinose, opaque, moderately thick, (9 –)10 –12.5(–13 %); medulla compact to dense (hyphae visible individually), very thin, 9 –11(–11.5 %); axis white, very thick (52.5 –)54 – 61(– 63.5 %), with an A/M-ratio > 4.5; apothecia and pycnidia not observed.
Chemistry. Medulla with salazinic acid [P+ yellow orange, K+ yellow turning deep red, C–, KC–].
Distribution and ecology. Presumably endemic to the Galapagos; it is a relatively rare species that mostly grows in the humid and upper transition zone, typically in exposed habitats, on fenceposts, small branches and twigs, shrubs and small trees.
Notes.Usnea patriciana can be recognized by the non-inflated branches bearing abundant tubercles, a distinctly black pigmentation at its base (although, unlike U. aff. columbiana not extending above the first ramification of the trunk), and by plane to slightly convex soralia remaining well-delimited by a thin cortical rim, even when crowded. In section its cortex appears mat and the axis is very broad (A/M-ratio > 4.5). The species belongs to a group of closely related species (see comments above on U. mayrhoferi). Most similar is U. brattiae, which, however, has a trunk that is mostly concolorous with the basal branches, rarely reddish brown. The trunk of U. patriciana is typically dark brown to blackish. Branches of U. patriciana are cylindrical to irregular, abundantly tuberculate, those of U. brattiae are regularly terete and lack tubercles. Soralia of U. patriciana are plane, distinctly delimited by a cortical rim. They are circular to elongate and at maturity become almost capitate, covering nearly the entire branch diameter. In U. brattiae soralia typically remain small and punctiform, they are not delimited by a rim. The cortex of U. patriciana is mat, thicker than the cortex of U. brattiae, which appears shiny in section. The medulla of both species is similar, compact, slightly thinner in U. brattiae. Usnea patriciana has an axis distinctly thinner than U. brattiae. The chemistry of U. brattiae appears to be more variable, with either salazinic or norstictic acid, sometimes with fatty acids, rarely with no secondary metabolites detected in its medulla. Only one chemotype is known from U. patriciana (salazinic acid).