TYPE. CANADA. British Columbia. Clearwater Valley, kame terrace north above Philip Creek, 51°52.182' N, 119°58.825' W, on branch of Pseudotsuga, 1000 m, 2009, T. Goward 09-640 with J. Hollinger (UBC, holotype; CANL, GZU, H, isotypes).
Description. Life form: lichenized fungus
Thallus (The following description is based on the "appressed" form only; see Notes, below): thin to somewhat thick, closely appressed to in part loosely appressed, but not trailing, without upturned tips or at most with weakly upturned tips, up to 3-6 (-8) cm across; branching at first even to more often uneven, becoming distinctly uneven in older portions of thallus; lobes hollow.
First tier (peripheral) lobes: proportionately rather short to somewhat elongate, readily divisible or not into main lobes and sparse to numerous, rather short lateral secondary lobes, these without basal constrictions, generally scarcely branched; broadest lobes 1-2 (-2.5) mm wide, distinctly uneven in width, usually contiguous (substrate not visible toward thallus periphery) or sometimes looser, the outermost ones often distinctly broadened or paw-shaped near the tips, lobe tips weakly convex to in part weakly concave, usually proliferating in threes, fours, fives or sixes. Second tier (interior) lobes: absent to occasionally becoming sparse, more or less appressed, except loosely overlapping in some thalli, readily distinguished from peripheral lobes, occasionally elevated above them. Upper surface: white to more often pale bluish, except sometimes blackening where exposed, rather shiny, almost "glassy," without black mottling but lobe tips sometimes heavily flecked with incipient brown pycnidia, smooth to weakly rugose at thallus periphery, often becoming more or less transversely pitted and ridged toward the thallus centre, often bearing tiny glassy "papillae" that mark the position of previously resorbed pycnidia (see below), weakly convex to weakly concave at the tips, becoming strongly convex toward the thallus center. Medullary ceiling: white except here and there dark brown in the vicinity of old ruptures in the lower surface. Lower surface: black, shiny; very thin, easily torn, sharply winkled or folded. Perforations: apparently absent. Vegetative propagules: absent. Apothecia: over upper surface, rather common, often clustered, usually with at least some young and poorly developed ones present, stalked, the "stipes" pale or often bearing black incrustations in upper portions, generally initially tapering downward to the base, later abruptly flaring to the expanded disc; disk concave, pale brown to dark brown, the largest ones 2-4 (-6) mm across; ascospores ellipsoid, averaging 6.0 (+/- 0.6 μm) × 4.7 (+/- 0.4 μm) µm, Q = 1.24 +/- 0.13, N = 112 / 8. Pycnidia: sparse to more often abundant over the upper surface toward lobe tips, forming tiny black or dark brown dots, these paler and becoming resorbed toward the thallus centre, usually not leaving black pits, sometimes later replaced by sparse to numerous tiny papillae; conidia rod-shaped c. 5.5-6.2 × 0.8-1.2 µm.
Chemistry. Spot tests: cortex K+ yellow, KC-, C-, PD- or occasionally PD+ pale yellow; medulla K+ slowly reddish pink (after 30 minutes!), KC+ pinkish (flash), C-, PD-. Lichen substances: Atranorin (localized in upper cortex), physodic acid (major, constant), 2-O-methylphysodic acid (submajor, sometimes in trace amounts or absent altogether), unknown C8 (trace, present in over half the specimens) and 2-methylene-3R-carboxy-18R-hydroxy-nonadecanoic acid (major, constant; = ‘apinnatic acid’, see below).
Substrate and ecology. Hypogymnia wilfiana grows exclusively on trees, especially conifers, e.g., Pseudotsuga, Abies, Picea and Tsuga. In some portions of its range it also colonizes Betula papyrifera, though it is not currently known from other deciduous trees and shrubs. It is generally absent from the driest forest types, becoming common in more humid regions, where it extends upward to treeline.
Distribution. (All three forms). Hypogymnia wilfiana is restricted to inland, mostly intermontane regions, ranging from the Yukon south to Washington and western Montana and, in Canada, into extreme western Alberta. Brodo et al. (2001) provide a generalized range map for H. wilfiana (under H. metaphysodes), though it should be noted that northwestern portions of the indicated range are likely to be based on H. canadensis (see the map in Goward & McCune 2007). Brodo et al. (2001) also mapped this species from northern California, southern Colorado and Ontario, but these records now require confirmation.