Type. [U.S.A.] COLORADO. [Clear Creek Co.], 40 miles west of Denver, on twigs of conifer, 8000 ft, October 1946, F.T. Lacey s.n. (UPS ‑ holotype!).
Description.Thallus thin, light grey‑brown to dark copper-brown, mostly discrete, convex verrucae, to 0.20-0.30 mm wide, or rarely continuous to rimose areolate; surface rugose, matt; margin determinate or not; prothallus absent; vegetative propagules absent. Apothecia broadly attached becoming narrowly attached, frequent, widely dispersed or contiguous, to 0.30‑0.60 mm diam.; disc dark brown, sometimes becoming black, plane or sometimes convex; thalline margin concolourous with thallus, entire or somewhat flexuose, persistent, 0.05(‑0.10) mm wide; excipular ring absent. ApothecialAnatomy. Thalline exciple 50‑65µ wide laterally; cortex 5‑10 µm wide laterally; epinecral layer absent; crystals absent in cortex and medulla; cortical cells pigmented or not, to 4.5‑6.0 µm wide; algal cells to 8.5‑13.0 µm long; thalline exciple 50‑80 µm below; cortex expanded to 10-20 µm when narrowly attached; proper exciple hyaline, 5‑10 µm wide laterally, to 10‑25 µm above; hypothecium 40‑70(-90) µm deep; hymenium 60‑80 µm high, not inspersed; paraphyses 2.0-2.5 µm wide, moderately conglutinate or not, apices to 4.0‑5.5 µm wide, lightly or heavily pigmented and immersed in dispersed pigment forming a red‑brown epihymenium; asci 40‑60(-70) x 14‑18 µm. Ascospores 8/ascus, developmental type A, Pachysporaria-type II, (12.0‑)14.5-15.5(‑18.5) x (6.5-)8.0‑8.5(‑10.0) µm, average l/b ratio 1.8-1.9, lumina irregularly angular prior to wall pigmentation (Physcia-like), becoming rounded, walls remaining thick, pigmented single celled spores common in some specimens, with apical thickenings (as in Type B development); torus dark, narrow at maturity; walls not ornamented. Pycnidia immersed in thallus; conidiophores Type I; conidia bacilliform, ca. 4.5 x 1.0 µm.
Chemistry. Spot tests all negative; secondary metabolites not detected.
Substrate and Ecology. A pioneer species of twigs and smooth bark of both coniferous and deciduous trees, R. coloradiana has sometimes been collected with R. boulderensis and once with R. metaboliza. Collected on Abies concolor, A. lasiocarpa, Acer glabra, A. grandidentata, Alnus oblongifolia, Picea englamanii, P. glauca, Pinus chihuahuana, Populus tremuloides, Prunus, Pseudotsuga menziesii, Quercus emoryi, Q. gambelii, Q. hypoleucoides and Robinia neomexicana, at elevations of 1,900-3,050 m.
Distribution. This North American endemic belongs to the Madrean floristic element. It is restricted to the drier areas of the western interior being distributed from the Black Hills, to the southern Rocky Mountains and south into Chihuahua Province, Mexico. This pattern of distribution is almost coincident with the Apachian and southern Rocky Mountain elements of McLaughlin (1989) with an extension into the Black Hills. Rinodina boulderensis has a similar distribution but extends further north with outliers in southern Alberta.
Notes. The Pachysporaria-type II spores of R. coloradiana make this species difficult to confuse with other corticolous and lignicolous montane western species. However, the presence of a torus (probably the well developed septum referred to by Magnusson 1952) and irregularly angular locules at early stages of development are similar to the Physcia-type. Mature one-celled spores possess thickened apical walls typical of Type B spore development are frequent in some specimens but this state has not been observed in immature, hyaline spores. There is no evidence of the K+ reaction in the thalline margin described by Magnusson.
The copper-brown thallus of many specimens and thallus habit are similar to R. septentrionalis as are the scattered, narrowly attached apothecia. Rinodina coloradiana is distinguished by its smaller, Pachysporaria-type II rather than Physcia‑type, spores at maturity. Western collections of R. freyi may also have a similar habit and thallus pigmentation and this species also differs in possessing Physcia-type spores but with a very prominent torus. In addition, R. coloradiana has been confused with the eastern R. pachysperma (Wetmore 1968) which has the same spore type but a better developed, areolate thallus, contiguous mostly broadly attached apothecia, and slightly larger spores with a less prominent torus.
Specimens examined. MEXICO. CHIHUAHUA, 20 km W Basadeachic, T.H. Nash 37705; road from Bavispe to Casa, T.H. Nash 36518 (both ASU). U.S.A. ARIZONA, Apache Co., Apache Nat. Forest, B.D. Ryan 27293; Escudilla Mountain, T.H. Nash 10678, 11818; Mt. Baldy Wilderness, T.H. Nash 27163; Cochise Co., Chiricahua Mountains, B.D. Ryan 10765b; T.H. Nash 41733, 41734 (all ASU); W.A. Weber 8853, 36921, 36935 (COLO); T.H. Nash 18517; Herb Mayr Dam, T.H. Nash 31996 (both ASU); Portal, W.A. Weber 8723, 14104 (COLO); Rustlers Park, T.H. Nash 3932a; Coconino Co., Oak Creek, T.H. Nash 35361; W Buzzard Point, T.H. Nash 35307; Gila Co., Sierra Ancha Station, T.H. Nash 26403; Workman Creek, T.H. Nash 9255; Graham Co., Apache Nat. Forest, T.H. Nash 41856; Goudy Canyon Research Area, T.H. Nash 16624; Pinaleno Mountains, T.H. Nash 14400, 13417a, 16543, 16582, 16628; Greenlee Co., Bear Wallow Wilderness, T.H. Nash 35037 (all ASU); Blue Vista Viewpoint, S.C. Tucker 37382 (SBBG); Hannagan Meadows, T.H. Nash 7718 (ASU, MSC); Pima Co., Marshal's Gulch, T.H. Nash 35447 (ASU); Mica Mountain, 1986, C.M. Wetmore 55029 (MIN); Mount Lemon, T.H. Nash 21197, 21198b 21205; Sabino Canyon, T.H. Nash 41684; Santa Catalina Mountains, T.H. Nash 35448; Santa Cruz Co., Florida Saddle Trail, T.H. Nash 25330; Taos Co., Taos Ski Area, T.H. Nash 22341 (all ASU). COLORADO. Boulder Co., Green Mountain, S. Shushan 4842 (COLO); Roosevelt Nat. Forest, L. Gough 562 (SASK); Clear Creek Co., Denver, 1946, F.T. Lacey (UPS); Grand Co., Gore Pass, S. Shushan 4917 (BRY); Rollins Pass, R.A. Anderson 6654 (COLM); Larimer Co., Forest Canyon, R.A. Anderson 3948. NEW MEXICO. Catron Co., Mogollon, W.A. Weber 41273 (both COLO); Otero Co., Cloudcroft, I.M. Brodo 30438 (CANL); near Cloudcroft, C.M. Wetmore 14395 (MIN); San Miguel Co., Dalton Canyon, I.M. Brodo 30500b (CANL); Las Vegas, W.A. Weber 58006 (COLO); Santa Fe Nat. Park, I.M. Brodo 30515 (CANL). SOUTH DAKOTA. Lawrence Co., Dalton Campground, C.M. Wetmore 10571a, (CANL, MSC); Pennington Co., Silver City, C.M. Wetmore 8904 (DUKE), 8909 (MIN, MSC, UPS).
References. Wetmore (1968 as R. pachysperma), Sheard (2004 Fig. 63).
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, comprised of small discrete, plane to convex areoles, up to c. 0.2 mm wide, sometimes becoming contiguous, plane to rugose surface: light gray-brown to dark copper-brown, dull; margin: determinate or not; prothallus: lacking; vegetative propagules: absent Apothecia: frequent, widely dispersed and sessile, or contiguous and adnate, up to 0.3-0.6 mm in diam. disc: dark brown, usually becoming black, plane to slightly convex thalline margin: concolorous with thallus, 0.05-0.1 mm wide, entire or somewhat flexuose, persistent; excipular ring: absent thalline exciple: 50-65 µm wide laterally; cortex: 5-10 µm wide; cells: up to 4.5-6 µm wide, pigmented; algal cells: up to 8.5-11 µm in diam.; thalline exciple: 50-80 µm thick below; cortex: sometimes expanded, c. 20 µm, cellular proper exciple: hyaline, 5-10 µm wide laterally, expanded to 10-20 µm wide at periphery hymenium: 60-80 µm tall; paraphyses: 1.5-2.5 µm wide, not conglutinate, with apices up to 3.5-5.5 µm wide, lightly or heavily pigmented, immersed in dispersed pigment, forming a red-brown epihymenium; hypothecium: hyaline, 40-90 µm thick asci: clavate, 40-60 x 14-17 µm, 8-spored ascospores: brown, 1-septate, broadly ellipsoid, type A development, Pachysporaria-type, (12.5-)15-16(-18.5) x (7-)8.5-9(-10) µm, lumina irregularly angular prior to wall pigmentation (Physcia-like), becoming irregularly rounded, walls remaining thick; torus: dark at maturity; walls: not ornamented (Fig. 63); pigmented, single celled spores common in some specimens, with apical thickenings (as in type B development) Pycnidia: immersed in thallus; conidiophores: Type I conidia: c. 4.5 x 1 µm Spot tests: all negative Secondary metabolites: none detected. Substrate and ecology: on twigs and smooth bark of both coniferous and deciduous trees; a pioneer species sometimes associated with R. boulderensis World distribution: a western North American endemic restricted to drier areas in the Black Hills and southern Rocky Mountains Sonoran distribution: frequent in Arizona, south into Chihuahua, at elevations of 1900-3050 Notes: The Pachysporaria-type spores of R. coloradiana make this species difficult to confuse with other montane western species on bark or wood. Forms with scattered apothecia and dispersed areoles are superficially similar to R. septentrionalis Malme, a boreal species that does not occur in the study area. Apothecia of both species are sessile and develop a slightly expanded lower cortex but R. coloradiana is distinguished by its Pachysporaria-, rather than Physcia-type spores. Sonoran collections of R. glauca may also have a similar habit and thallus pigmentation but this species differs in possessing Physcia-type, although similar sized spores with a prominent torus.