Type. U.S.A. COLORADO. Boulder Co., Bluebell Canyon, base of Flatirons, near Boulder, on Acer glabrum, 6000 ft (1830 m), 5 February 1954, W.A. Weber and S. Shushan S1473 (COLO - holotype!; WIS - isotype!).
References. Wetmore (1968 as R. exigua), Sheard & Mayrhofer (2002 Fig. 6), Sheard (2004).
Diagnosis.Thallus thin, light grey, continuous, or more usually rimose‑areolate; areoles to 0.50-1.20(-1.60) mm wide; surface plane or rugose, matt; margin determinate; prothallus lacking; vegetative propagules absent.
Description.Apothecia often erumpent, remaining broadly attached, frequent, often contiguous, to 0.35-0.60(-0.70) mm in diam.; disc black, plane, becoming slightly convex; thalline margin concolourous with thallus, ca. 0.10 mm wide, entire, subcrenulate in thicker thalli, persistent or often incompletely developed in part, then replaced by a thin, pigmented proper exciple; excipular ring otherwise absent. Apothecial Anatomy. Thalline exciple 60-110 µm wide; cortex 5-10 µm wide; epinecral layer absent; crystals present in cortex, absent in medulla; cortical cells to 3.5-6.0 µm wide, not pigmented; algal cells to 11.0-15.0 µm long; proper exciple hyaline, 5-10 µm wide laterally (wider and pigmented where thalline exciple absent), expanding to 10-25 µm wide at periphery; hypothecium (20-)60-80(-100) µm deep; hymenium 60-110 µm high, not inspersed; paraphyses 1.5-2.0 µm wide, often conglutinate, with apices expanded to 3.5-5.0 µm wide, lightly pigmented, immersed in dispersed pigment, forming a red‑brown epihymenium; asci 50-60 x 14-18 µm. Ascospores 8/ascus, developmental Type A, Physcia‑type (Figure 27), (13.0-)16.0-17.0(-19.5) x (7.0-)8.0-9.0(-10.0) µm, average l/b ratio 1.9-2.1, lumina persistently angular or finally becoming rounded, maintaining thick apical wall; torus becoming darkly pigmented; walls not ornamented. Pycnidia infrequent, deeply immersed in thallus with only pigmented ostiole visible; conidiophores Type II; conidia bacilliform, 3.5-5.0 x ca. 1.0 µm.
Chemistry. Spot tests, K - or mostly K+ yellow, C - , KC - , P - or P+ faint yellow; secondary substances, atranorin in cortex.
Substrate and Ecology.Rinodina boulderensis has been collected on conifers and deciduous trees, including Abies concolor, Acer glabrum, A. grandidentata, Alnus, Juniperus deppeana, Picea, Pinus flexilis, Populus tremuloides, Pseudotsuga menziesii, Quercus gambelii, Q. hypoleucoides, and rarely on wood. It has been collected with R. archaea, R. aurantiaca and most frequently with R. coloradiana.
Distribution. A western North American endemic that has a Rocky Mountain distribution extending from southern Alberta to Arizona where it has been collected most frequently. Outlier populations are found in the Black Hills and Baja California where it occurs at its highest known elevation of 2,800 m. This pattern of distribution is similar to that of R. coloradiana and the Apachian and southern Rocky Mountain elements of McLaughlin (1989), with northern extensions.
Notes. The light grey, K+ yellow thalli of R. boulderensis, often with slightly convex apothecia, have a similar habit to R. aurantiaca and R. capensis. Both these species are easily distinguished by possessing apothecia with a columnar lower cortex and larger spores. Rinodina boulderensis can usually be recognized by its relatively small apothecia and their often incompletely formed thalline margins. The spores of R. freyi are similar in size, also possess a darkly pigmented torus and lack wall ornamentation which may indicate a taxonomic relationship. Rinodina freyi can be distinguished by its dark grey to copper-brown thallus, confluent, brown excipular ring, and lack of atranorin.
Rinodina boulderensis may be related to R. exigua (Ach.) Gray which is only known from California in North America. Rinodina exigua is distinguished by an indistinct cortex and spores which are larger, possess a less well developed and less pigmented torus, and have quite strongly ornamented walls.
Specimens examined [and not recorded by Sheard & Mayrhofer (2002)]. CANADA. ALBERTA. 2 mi W Brocket, C.D. Bird 20100; Bearspaw Dam, C.D. Bird 19553 (both PMAE). MEXICO. BAJA CALIFORNIA NORTE. San Pedro Matirs, T.H. Nash 14713 (ASU). U.S.A. ARIZONA. Cochise Co., Hauchuca Mts, T.H. Nash 14572; Rustler Park, T.H. Nash 3932c; Coconino Co., 10 mi S Flagstaff, I.M. Brodo 20289 (all ASU), 20333 (CANL); Grandview Trail, T.H. Nash 31039; Oak Creek Canyon, S.C. Tucker 12445; T.H. Nash 9283a; W fork Oak Creek, E. Lehto 72b; Gila Co., Pine Canyon, T.H. Nash 42002; W side Aztec Peak, A. Olafsen 51; Workman Creek, T.H. Nash 28430; Graham Co., Pinaleno Mts, T.H. Nash 16527, 16582, 16600, 16613b, 35980, 36002; Shannon Camp, R.A. Darrow 1850, 1856 (all ASU); Greenlee Co., Blue Vista Viewpoint, S.C. Tucker 37381 (SBBG); Pima Co., Mica Mountain, C. M. Wetmore 55022, 55028, 55029, 55084; N Spud Rock, C.M. Wetmore 54522 (all MIN); Santa Catalina Mts, T.H. Nash 35447 (ASU); below Manning Campground, C.M. Wetmore 54601 (MIN). COLORADO. Boulder Co., Bluebell Canyon, W.A. Weber S1473 (COLO, WIS); Boulder, W.A. Weber S1471 (COLO); Gregory Canyon, J.W. Sheard 4663, 4669b (SASK). NEW MEXICO. Bernadillo Co., Sandia Mountains, S.C. Tucker 37288b (SBBG). SOUTH DAKOTA. Lawrence Co., 3 mi W Piedmont, C.M. Wetmore 9210; Dalton Campground, C.M. Wetmore 10571a (both MSC).
Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2004. Lichen Flora of the Greater Sonoran Desert Region. Vol 2.
Thallus: crustose, thin, continuous, or more usually rimose-areolate, areoles up to 0.5-1.2(-1.6) mm wide, plane or rugose surface: light gray, dull; margin: determinate; prothallus: lacking; vegetative propagules: absent Apothecia: often erumpent, remaining adnate, frequent, often contiguous, up to 0.35-0.6(-0.7) mm in diam. disc: black, plane, becoming slightly convex thalline margin: concolorous with thallus, c. 0.1 mm wide, entire, subcrenulate in thicker thalli, persistent or often incompletely developed in part, then replaced by a thin, pigmented proper exciple; excipular ring: otherwise absent thalline exciple: 60-110 µm wide; cortex: 5-10 µm wide; cells: up to 3.5-6 µm wide, not pigmented; algal cells: up to 11-15 µm in diam. proper exciple: hyaline, 5-10 µm wide laterally, expanding to 10-25 µm wide at periphery hymenium: 60-110 µm tall; paraphyses: 1.5-2 µm wide, often conglutinate, with apices expanded up to 3.5-5 µm wide, lightly pigmented, immersed in dispersed pigment, forming a red-brown epihymenium; hypothecium: (20-)60-80(-100) µm thick asci: clavate, 50-60 x 14-18 µm, 8-spored ascospores: ellipsoid, brown, 1-septate, developmental Type A, Physcia-type, (13-)16-17(-19.5) x (7-)8-9(-10) µm, lumina persistently angular or finally becoming rounded, maintaining thick apical wall; torus: becoming darkly pigmented; walls: not ornamented Pycnidia: infrequent, deeply immersed in thallus with only pigmented ostiole margin visible; conidiophores: Type II; conidia: bacilliform, 3.5-5 x c. 1 µm Spot tests: K- or mostly K+ yellow, C-, KC-, P- or P+ faint yellow Secondary substances: atranorin in cortex. Substrate and ecology: on conifers and deciduous trees, and rarely on wood World distribution: a western North American endemic that has a Rocky Mountain distribution extending from southern Alberta to Colorado and into Arizona where it has been most frequently collected Sonoran distribution: Arizona and Baja California, where it occurs at its highest known elevation of 2800 m. Notes: The light gray, K+ yellow thalli of R. boulderensis, often with slightly convex apothecia, have a similar habit to R. aurantiaca and R. capensis. Both these species are easily distinguished by possessing apothecia with a columnar lower cortex and larger spores. Rinodina boulderensis can usually be recognized by its relatively small apothecia and their often incompletely formed thalline margins. The spores of R. glauca are similar in size, also possess a darkly pigmented torus and lack wall ornamentation, and taken together these may indicate an evolutionary relationship. Rinodina glauca is easily distinguished by its dark gray thallus and lack of atranorin. Rinodina boulderensis may be related to R. exigua (Ach.) Gray, whose occurrence in North America is questionable. Rinodina exigua is distinguished by possessing spores, that have a less well developed and less pigmented torus, and apothecial margins, that are always fully developed but may become excluded.