Diagnosis.Thallus areolarum typice dispersorum, convexorum; blastidia et soredia destitutus. Apothecia primo erumpentes vel adnata, celeriter sessilescentia; medulla et corticex sine crystallis. Ascosporae octonae, in modem A. evolutae, formae Physconia, (22.5-)27.0-28.5(-33.5) x (10.5-)13.0-13.5(-16.0) µm; paries foveolatus.
Type. CANADA. ONTARIO. Cochrane District, mouth of the Moose River, NE of Moosonee, on Salix, 51.21N 80.30W, 3 July, 1969, I.M. Brodo 14735 with J. Fabiszewski (CANL ‑ holotype).
Reference. Thomson (2003 as R. turfacea).
Description.Thallus thin, light or dark grey to grey‑brown, rarely dark brown, usually of scattered, convex areoles, to 0.25‑0.50 mm wide, sometimes minutely lobed at the margins, or continuous to rimose‑areolate; areoles 0.25-0.60 mm wide; surface plane or rugose, matt or shining; margin determinate or not; prothallus lacking. Apothecia erumpent and/or broadly attached at first, quickly becoming narrowly attached, frequent, scattered, becoming contiguous, to 0.60‑1.15 mm in diam.; disc brown becoming black, plane becoming slightly convex in largest apothecia; thalline margin concolourous with thallus, ca. 0.10 mm wide, sometimes lighter than thallus in young apothecia due to flaking of epinecral layer, entire, persistent, becoming flexuose in larger apothecia, cortex often visible around circumference when moistened; excipular ring rarely present, raised. Apothecial Anatomy. Thalline exciple 60‑80 µm wide laterally; cortex 10‑15 µm wide; epinecral layer 5‑10 µm wide; crystals absent in cortex and medulla; cortical cells to 5.5‑6.0(-8.5) µm wide, usually pigmented; algal cells to 11.5‑17.0 µm long; thalline exciple 90‑130(-150) µm below; cortex expanded to 30‑50 µm deep, cellular, or with intricate to columnar hyphae, sometimes I+ blue; proper exciple hyaline or yellowish, 10-20 µm wide laterally, 20‑30 µm above; hypothecium yellowish, inspersed with oil, 50‑90 µm deep; hymenium 90‑140 µm high, not inspersed; paraphyses 2.0‑3.5 µm wide, conglutinate, apices to 4.0‑6.0 µm, lightly pigmented, immersed in dispersed pigment to form a red‑brown epihymenium; asci 80‑90 x 20‑28 µm. Ascospores 8/ascus, developmental type A, Physconia-type, (22.5-)27.0-28.5(-33.5) x (10.5-)13.0-13.5(-16.0) µm, l/b ratio 2.0-2.3, often slightly constricted at maturity, cells sometimes with more darkly pigmented bands, lumina at first Physcia-like, becoming inflated, canals then excluded, apical walls rounded, but sometimes retaining slight thickening; torus well developed in early stages of development, sometimes causing narrow swelling at transverse wall; walls ornamented (x1250). Pycnidia not completely immersed, ca. 120 µm in diam., ostiole brown; conidiophores to 4 cells long, unbranched, type VI; conidia bacilliform, 5.5-6.5 x 1.0-1.5 µm.
Chemistry. Spot tests all negative; secondary metabolites not detected.
Substrate and Ecology. Corticolous, mainly on trunks of Populusbalsamifera and P. tremuloides but also on other species including P. grandidentata, P. trichocarpa, Abies balsamea, Acer rubrum, A. saccharum, Alnus crispa, Betula alleghaniensis, B. papyrifera, Picea glauca, Prunus virginiana, Salix bebbiana and Thuja occidentalis, rarely on twigs. The species has been collected from elevations of 50 m in coastal southern Alaska to 1 050 m in Montana. Rinodinaaustroborealis has been collected most frequently with R. metaboliza but also with R. colobina, R. laevigata, R. pachysperma, R. populicola, R. pyrina and R. subminuta.
Distribution. A North American endemic with a mainly southern Boreal distribution. Rinodina austroborealis is most frequent in the southern boreal forest, and extends southwards into the United States in Washington State and Montana in the west, and into Minnesota, Michigan and Wisconsin in the east. The species occurs northwards to western Alaska, the western Northwest Territories between 126o and 130o west longitude, into James Bay and along the south shore of Hudson Bay, following the distribution of one of its primary hosts, Populus balsamifera. A record of R. turfacea from the Apostle Islands, Wisconsin (Wetmore 1990, Thomson 2003) refers to this species. Specimens of R. austroborealis were included under R. ascociscana and Physcia adglutinata (Flörke) Nyl. by Fink (1910, 1935).
The truncation of the distribution of this southern boreal species at the Quebec border in the east requires further comment. The species may have survived the Pleistocene glaciation to the southwest of the ice sheet, or perhaps other western refugia, and has not yet had time to extend its range further east into Quebec and Newfoundland and Labrador where most of its substrate species are also present. It does not occur in the Alaskan interior or in the Yukon so there is no reason to think that it survived the ice-age in these more continental ice free areas. It is possible that the species has southern Beringian origins and it should be sought west of the Bering Straits.
Notes. This new species was first mistaken for a corticolous form of R. turfacea in the southern boreal zone. However, R. austroborealis differs from that species in the presence of ornamented spore walls, Physconia-type spores at maturity, and the lack of sphaerophorin. The southern boreal distribution of R. austroborealis is distinct from that of the primarily oro-arctic R. turfacea but which may also be corticolous in the boreal zone (Mayrhofer & Moberg 2002).
Rinodina ascociscana is another large spored corticolous species which has been confused with R. austroborealis. It is distinguished by its longer, Physcia-type spores (averaging 30.0-32.0 µm long) and its continuous, sometimes subsquamulose, plane rather than rugose thallus. Note that, other than size, the spores of the two species are actually quite similar despite those of R. austroborealis being described as belonging to the Physconia-type. The spores of R. ascosiscana have slightly thickened apical walls but are rarely thin walled, while the latter have mostly thin apical walls which rarely may remain slightly thickened. There is very little overlap in range between these two species, R. austroborealis being absent from the St. Lawrence River region while R. ascociscana is common in this area and in the northeastern United States and southwards down the Appalachian chain. Both species occur in the Great Lakes region but R. ascociscana is absent from the north shore of Lake Superior and R. austroborealis is very rare on the south shore.
Rinodina austroborealis may be related to R. sibirica which also often possesses erumpent apothecia, has similar spores with ornamented walls and also lacks secondary metabolites. The spores of R. austroborealis, however, are much larger than those of R. sibirica (average 20.5-21.5 x 10.0-10.5) and which typically possess slightly thickened apical walls and therefore mostly belong to the Physcia-type. Rinodina sibirica further differs in its apothecia being very narrowly attached, almost stipitate, and in having less prominent thalline apothecial margins which also become excluded with increasing convexity of the discs. It has a more northerly distribution than R. austroborealis, in the lichen woodlands of the subarctic region and further north.
Specimens examined. CANADA. ALBERTA. 6 mi W Chip Lake, C.M. Wetmore 20192 (MIN); Buffalo Lake Narrows, I.M. Brodo 27890 (CANL); Carrot Creek, P.A. MacNeil 967 (PMAE); Elk Island Nat. Park, G.W. Scotter 640 (CANL); Heatherdown Bog, 1971, C.M. Wetmore (GZU); Mitsue Lake, 1968, H.G. Anderson (PMAE); Slave Lake townsite, H.G. Anderson 334‑1. MANITOBA. Duck Mountain Prov. Park, East Blue Lake, 1997, J.W. Sheard (both SASK); York Factory, J.C. Ritchie 4105B. N.W.T. Mackenzie District, Mountain River, J.W. Thomson 20019 (both WIS); 1 mi E Norman Wells, C.D. Bird, 35165 (PMAE); 5 mi SE Norman Wells, J.W. Thomson 19934, 19962 (WIS); 70 mi WNW Norman Wells, C.D. Bird 27483 (PMAE); Arctic Red River, J.W. Thomson 19828; Keele River, G.W. Scotter, 15911; J.W. Thomson 15542, 15634; Mackenzie Mountains, G.W. Scotter 15130; Mountain River, J.W. Thomson 20018 (all WIS). ONTARIO. Cochrane District, Fort Albany, T. Ahti 3736B; Martison Lake, T. Ahti 3974 (both H); Moose Factory Island, I.M. Brodo 14683; Moosonee, I.M. Brodo 14638 (both CANL), 14735 (CANL, PMAE); Kenora District, Attawapiskat, T. Ahti 3742, 4957B (H); Kapiskau River, G.S, Ringius 10 (CANL); Winisk, T. Ahti 3990 (H); Thunder Bay District, 20 mi W Rossport, F.H. Erbisch 823 (MSC); Brule Bay, J.W. Sheard 1579B (SASK); Kakabeka Falls, I.M. Brodo 13641, 13645 (CANL); J.W. Sheard 1592C (SASK); Lake Nipigon, 1884, J. Macoun; Mount McKay, I.M. Brodo 13546 (both CANL); J.W. Sheard 1562D (SASK); Nipigon Bay, I.M. Brodo 6266 (CANL); Ouimet Canyon, I.M. Brodo 6034 (CANL, PMAE). SASKATCHEWAN. 40 km W Melfort, J.W. Sheard 5215; 5 mi NE Duck Lake, 1992, J.W. Sheard; Anglin Lake, 1994, J.W. Sheard; Beaver Creek, J.W. Sheard 1826 (all SASK); Montrose, 1958, J. Looman 10.05 (SCS); Prince Albert Nat. Park, Kingsmere Lake, J.A. Jesberger 1257; Waskesiu, J.A. Jesberger 935, 1104; Saskatoon, 1992, J.W. Sheard (all SASK). U.S.A. ALASKA. E Palmer, T. Tønsberg 29690 (BG); Kodiak NWR, Spiridon Peninsula, S.S. Talbot 151‑41 (WIS). MICHIGAN. Keweenaw Co., Isle Royale Nat. Park, Mount Ojibway, C.M. Wetmore 2249b, 2253, 48073, 49121, 49722, 52190, 52618, 53049. MINNESOTA. Clay Co., Buffalo River State Park, C.M. Wetmore 74531; Cook Co., Grand Portage, 1897, B. Fink; Gunflint Lake, 1897, B. Fink 34; Sugar Loaf Preserve, C.M. Wetmore 75300; Tofte, 1897, B. Fink 594; Lake Co., Snowbank Lake, 1897, B. Fink 853, 875; St. Louis Co., Voyageurs Nat. Park, C.M. Wetmore 33827, 31589, 33861, 35374 (all MIN). MONTANA. Flathead Co., Glacier Nat. Park, A. DeBolt 2007c (personal herb.); N Fork Flathead River, B. McCune 19194 (personal herb.). OREGON. Deschutes Co., S South Sister Mountain, B. McCune 17310 (personal herb.). WASHINGTON. Kittitas Co., SW Kachess Lake, T. Tønsberg 26959 (BG). WISCONSIN. Ashland Co., Hermit Island, C.M. Wetmore 60067 (MIN).