Description.Thallus thin, a shade of grey, often bluish-grey (particularly when wet), sometimes scabrid, usually continuous or rimose-areolate; areoles to 0.20‑0.30 mm wide; surface plane to rugose, matt; margin indeterminate; prothallus absent; vegetative propagules present; typically with dense consoredia 20‑45 µm diam., usually darker than thallus, to blackish, developing on areole margins, later covering thallus surface. Apothecia broadly attached to narrowly attached, frequent, contiguous or not, to 0.25-0.70 mm in diam.; disc black and persistently plane; thalline margin concolourous with thallus or lighter, entire and persistent, 0.05‑0.10 mm wide; excipular ring often present, raised. Apothecial Anatomy. Thalline exciple 45‑60 µm wide laterally, cortex 10‑15(‑25) µm wide; epinecral layer absent; cortical cells to 5.0‑6.5 µm wide, not pigmented but in darker thalli immersed in dispersed blue pigment, K+, N+ purplish-red; algal cells to 9.5-16.5 µm long; thalline exciple 50‑90 µm wide below; cortex 10‑30 µm deep, cellular or intricate; proper exciple hyaline, 10‑25 µm wide laterally, expanding to 15‑40 µm at periphery; hypothecium colourless, 40‑50 (‑80) µm deep; hymenium 75‑100 µm high, not inspersed; paraphyses 2.0‑3.0 µm wide, strongly conglutinate, apices expanded to (3.0‑)4.0‑5.0 µm wide, not or hardly pigmented, immersed in dispersed pigment forming a blue-grey epihymenium reacting K+, N+ dark purplish-red; asci: 50-75 x 16-23 µm, 8-spored. Ascospores developmental Type A or B, Dirinaria-type (Figure 44), 15.0‑(17.5‑18.0) ‑20.5, 18.0 x 9.1, 7.0‑(8.5‑9.5)‑11.0 µm, average l/b ratio 1.9-2.0, some slightly inflated at septum, mature spores sometimes more swollen in KOH, lumina Physcia- to Mischoblastia-type, becoming rounded but spore canals more or less persistent; torus: absent; walls: not ornamented. Pycnidia not found.
Chemistry. Spot tests all negative; secondary metabolites not detected.
Substrate and Ecology. The species has been collected on Acer saccharum, Juniperus, Populus balsamifera, P. deltoides, P. tremuloides, P. trichocarpa, Quercus macrocarpa, Sorbus and Ulmus, rarely on wood. It is most commonly collected on Populus balsamifera and P. tremuloides. Recorded at elevations of 395-1,675 m. Rinodina colobina has been collected with R. austroborealis, R. metaboliza, R. oregana, R. populicola and R. pyrina.
Distribution. This species has a southern Boreal and Parkland distribution in the continental interior extending as far south as South Dakota, and with an outlier locality in the California Coastal Ranges. The species is notably absent from Quebec and the northeastern seaboard where its two principle host species occur. In this respect its distribution is similar to that of R. austroborealis although it does not extend as far north. It is also known from central and southern Europe, scattered in southern Scandinavia, northern Africa and Asia (Mayrhofer and Moberg 2002). Fink (1910, 1935) collections were included under R. sophodes (Ach.) A. Massal.
Notes. Rinodina colobina is characterized by its blue-grey, K+, N+ purplish-red epihymenium, grey thallus and dark consoredia with the same reaction in section. The spores of R. colobina are relatively thick walled and have rounded lumina at maturity. Ropin and Mayrhofer (1995) describe the spores as showing developmental similarities with the Pachysporaria-, Physcia- and Mischoblastia-types. Giralt (2001) describes them as belonging to the Mischoblastia-type. The spore lumina are certainly developmentally very variable and is this respect they are reminiscent of those of R. gennarii. They may also display Type B development, but this is clearly a very transient phenomenon since no more than two spores have been observed in this state in any single ascus and it is typically absent. Immature spores may also be slightly swollen at the septum and a few mature spores may become inflated at the septum with KOH. For these reasons the spores are here regarded as belonging to the Dirinaria-type. Note that the illustration of spores in Fox and Purvis (1992, Figure 25d) refers to R. pityrea Ropin & H. Mayrhofer rather than to R. colobina.
Rinodina lobulata is the only other corticolous species with a similar epihymenium pigment but its spores belong to the Beltraminia-type, and suggests that there is no close taxonomic relationship. In Europe, two other corticolous species are known with the same epihymenium pigment, R. mayrhoferi and R. pityrea Ropin and Mayrhofer, with Bicincta- and Tunicata-type spores respectively (Ropin & Mayrhofer 1995). Evidently, the pigment has evolved a number of times within the genus.
Rinodina colobina has a rather variable thallus colour and morphology. In shaded habitats the thallus is relatively light grey in colour, the consoredia are either absent or poorly developed and the thallus is composed of discrete areoles. Substrates exposed to sunlight have darker thalli, rarely almost black, tend to be continuous, and possess abundant darkly pigmented consoredia (Tønsberg 1992). Such variation may sometimes be observed on the bark microtopography of individual host trees with deeply fissured bark such as Populus balsamifera. Ropin and Mayrhofer (1995) and Giralt (2001) describe the vegetative propagules as blastidia. The thalli of R. colobina may also occur in association with filamentous blue‑green algae which also give light coloured thalli a dark aspect.
Specimens examined. CANADA. ALBERTA. Bowness, P.J. Schofield 437; 1.6 mi W Castle River, C.D. Bird 21330 (both PMAE); W Block, Cypress Hills Interprov. Park, J.W. Sheard 5224 (SASK); Winfield, I.M. Brodo 31257c (CANL). BRITISH COLUMBIA. Mt. Robson Prov. Park, C.D. Bird 23564 (PMAE); N Sirdar, J.W. Sheard 5277 (SASK). MANITOBA. East Blue Lake, 1997, J.W. Sheard; Red Deer River, J.W. Sheard 5209a (both SASK). ONTARIO. Cochrane Dist., Moose Factory, I.M. Brodo 14684; Kenora Dist., Vermillion Bay, I.M. Brodo 16012; Thunder Bay Dist., 3 ml N Nipigon, I.M. Brodo 13513 (all CANL); Mount Mckay, J.W. Sheard 1559b (SASK); C.D. Bird 20331 (PMAE). SASKATCHEWAN. 17 km W Hudson Bay, J.W. Sheard 5214; Batoche Bridge, 1994, J.W. Sheard; Crean Lake, J.A., Jesberger 1131; Eastend Campground, J.W. Sheard 5227; Emma Lake, J.W. Sheard 4700; Kenosee Lake, J.W. Sheard 5257; Miko Lake, J.W. Sheard 5247 (all SASK); Prince Albert Nat. Park, J.A., Jesberger 874 (WIS); 1994, J.W. Sheard; Ravenscar, J.W. Sheard 5225, 5226; Shell Lake, J.W. Sheard 5248 (all SASK). U.S.A. CALIFORNIA. Lake Co., Clear Lake State Park, S.C. Tucker 31704 (SBBG). IDAHO. Benewah Co., Mashburn Station, B. McCune 25926a; 2.4 mi SE St. Maries, J. Hutchinson 72107; Shoshone Co., Fly Creek Campground, E. Martin 42b (all McCune personal herb.). MICHIGAN. Keweenaw Co., Conglomerate Bay, C.M. Wetmore 49463; Isle Royale Nat. Park, C.M. Wetmore 41318; Robinson Bay, C.M. Wetmore 49717 (all MIN); Mackinac Co., Big Knob Road, 1977, J. Poelt (GZU); 1974, H. Crum (MICH); R.C. Harris 12389 (UMBS). MINNESOTA. Cook Co., 1.5 mi SSE Phoebe Lake, T.D. Trana 14881 (MIN); Grand Portage, 1897, B. Fink (MIN, MSC, UC); Hubbard Co., Itasca State Park, C.M. Wetmore 23149, 35951; Koochiching Co., B. Fink 939 (both MIN); Lake Co., Beaver Bay, B. Fink 702 (MU). MONTANA. Gallatin Co., Hyalite Canyon, B. McCune 26004; Glacier Co., Glacier Nat. Park, B. McCune 26224 (both personal herb.). NORTH DAKOTA. Billings Co., Medora, C.M. Wetmore 45451 (MIN); McKenzie Co., T. Roosevelt Nat. Park, C.M. Wetmore 44607 (WIS); Watford City, C.M. Wetmore 44258, 44491, 44518, 44607, 44663, 44862; Williams Co., 21 mi E Williston, T.D. Trana 4442b (all MIN). SOUTH DAKOTA. Meade Co., Piedmont Butte, C.M. Wetmore 10404b (MSC); Pennington Co., Rapid City, R.A. Anderson 20556 (COLO); Shannon Co., Fog Creek Drainage, S. Will‑Wolf 2588 (WIS). WASHINGTON. Columbia Co., Lewis & Clark Trail State Park, B. McCune 18134 (personal herb.). WYOMING. Crook Co., Barlow Canyon, C.M. Wetmore 11463; N Moore Hill, C.M. Wetmore 11607 (both MSC).