taxonID	type	description	language	source
03ED879C762F90638083460F7A1B93AF.taxon	materials_examined	TYPE. USA, Colorado. Delta County. Gunnison National Forest, CR 265, lower montane stand of Populus tremuloides and Picea pungens, corticolous on P. pungens, 8710 ft. elev., 39.124 568, - 107.54828, 13 May 2024, E. Manzitto-Tripp & J. Watts 10446 (Holotype: COLO!). Figures 1 – 2 & 7. Mycobank #. 860001	en	Manzitto-Tripp, Erin A., Watts, Jacob L. (2025): The Thin Horizon of a Plan is Almost Clear: Towards a Lichen Biodiversity Inventory of the Southern Rocky Mountains, USA. Phytotaxa 712 (3): 207-229, DOI: 10.11646/phytotaxa.712.3.1, URL: https://doi.org/10.11646/phytotaxa.712.3.1
03ED879C762F90638083460F7A1B93AF.taxon	description	Description. Thallus light gray to pale greenish gray, not continuous, irregularly areolate to bullate, the areoles sometimes producing small lobules, epruinose. Apothecia sessile and constricted at the base, prominent, 0.5 – 1.2 mm in diameter, occurring in irregular clusters, less commonly solitary. Discs distinctly indigo blue, invariably densely pruinose, slightly concave to plane. Margins white, mostly entire to occasionally incised / cracked, corticate, much lighter in color compared to the thallus, strongly raised above disk. Parathecium hyaline, inconspicuous. Amphithecium 74 – 112 μm thick, apical portions of cortex (26 –) 29 – 37 (– 47) μm thick, lower portions of cortex extremely well-developed and prominent, (40 –) 53 – 75 (– 90) μm thick, the upper and lower cortices as well as algal layer containing fine POL + crystals, not dissolving in K, dissolving in N. Epihymenium brownish gray, containing fine POL + crystals, not dissolving in K, C, or N, also with a conspicuous indigo-colored pigment interspersed among paraphyses tips, indigo pigment not dissolving in K but dissolving in C, reacting pale red in N, (10 –) 13 – 30 (– 37) μm tall, with fine POL + crystals, not dissolving in K or N. Hymenium hyaline, densely inspersed with oil droplets, (43 –) 69 – 88 (– 100) μm tall. Hypothecium hyaline, (30 –) 55 – 65 μm tall. Asci with 8 spores per ascus, 32 – 38 (– 42) × cylindrical, frequently branched toward the apex, 1.5 – 2.5 μm wide apically, 1.0 – 1.5 μm basally. Ascospores simple, hyaline, subspherical to broadly ellipsoidal, (8 –) 9 – 11.5 × (5 –) 6 – 7, 1.4 to 1.7 (– 2.1) times longer than wide, sometimes surrounded by a thin, hyaline ring ca. 0.2 – 0.3 μm thick. Pycnidia not seen. Photobiont chlorococcoid, spherical 7 – 15 (– 18) μm in diameter.	en	Manzitto-Tripp, Erin A., Watts, Jacob L. (2025): The Thin Horizon of a Plan is Almost Clear: Towards a Lichen Biodiversity Inventory of the Southern Rocky Mountains, USA. Phytotaxa 712 (3): 207-229, DOI: 10.11646/phytotaxa.712.3.1, URL: https://doi.org/10.11646/phytotaxa.712.3.1
03ED879C762F90638083460F7A1B93AF.taxon	etymology	Etymology. The new species is named in honor of Indigo Girls, a now five-decade musical duo and legend that has inspired millions of listeners with their lyrical contributions, commitment to environmental protection, and social activism. Emily Saliers and Amy Ray of Indigo Girls have been major proponents of climate justice and, for years, led grassroots-style campaigns to increase awareness and promote change in social atmospheres. Songs by Indigo Girls have universally conveyed an interconnectedness between environmental health and social rights, which reminds us of lichen biodiversity and our parallel need to continue advancing initiatives that promote education and awareness of these remarkable symbiotic organisms. The new species further reminds us of Indigo Girls because it is both lustrous and assertive, introspective yet audacious, and reflective of voices that have not yet been heard, until now. Chemistry. Spot Tests: K, - C-, KC-, P- UV- (thallus and apothecia). Thin Layer Chromatography: No substances detected.	en	Manzitto-Tripp, Erin A., Watts, Jacob L. (2025): The Thin Horizon of a Plan is Almost Clear: Towards a Lichen Biodiversity Inventory of the Southern Rocky Mountains, USA. Phytotaxa 712 (3): 207-229, DOI: 10.11646/phytotaxa.712.3.1, URL: https://doi.org/10.11646/phytotaxa.712.3.1
03ED879C762F90638083460F7A1B93AF.taxon	distribution	Distribution. Current data document the presence of Lecanora indigoana only from Delta and Pitkin Counties, Gunnison National Forest, in central-western Colorado. We expect that additional collection efforts throughout Colorado and the southern Rocky Mountains, as well as further study of existing herbarium materials, will in time reveal a broader geographical distribution of this remarkable species. Substrate & Habitat. Lecanora indigoana has been found in lower montane forests occurring on two of Colorado’s most iconic tree species: Quaking Aspen (Populus tremuloides) and Blue Spruce (Picea pungens). Future lichenological fieldwork throughout the southern Rocky Mountains in similar habitats is likely to expand the known range of this species into comparable habitats, and potentially on additional substrates. Notes. The most immediately recognizable and distinguishing features of Lecanora indigoana (Figure 2) are its densely pruinose apothecial discs that are unwaveringly deep indigo in color. Because of these two traits, in North America Lecanora indigoana is likely only confusable for four other taxa that sometimes bear heavily pruinose discs appearing bluish to slate-colored: L. juniperina Śliwa, L. wetmorei Śliwa, L. invadens H. Magn., and L. perpruinosa Fröberg. Of these, only L. juniperina and L. wetmorei are similarly corticolous like the new species (note: the latter two are also lignicolous). Phylogenetic analyses resolved our two accessions of L. indigoana as reciprocally monophyletic with strong support (99 % bootstrap [BS]) and sister to L. juniperina, also with strong support (100 % BS). Lecanora indigoana can be differentiated from L. juniperina by the former’s conspicuous areoles that sometimes produce small lobules, its prominent indigo pigment interspersed among paraphyses tips, its inspersed hymenium that is taller than that of L. juniperina, its brownish gray (vs. yellow granular) epihymenium, its spores that are slightly shorter and wider, and its complete lack of secondary metabolites (vs. unknown xanthones in L. juniperina). Furthermore, whereas L. juniperina is currently known most predominantly from low elevations, primarily pinyon-juniper habitats of the Colorado Plateau, so far as understood, L. indigoana occurs in middle montane forests east of the Colorado Plateau at higher elevations such as those dominated by aspen and blue spruce. With L. wetmorei the new species shares relatively large apothecia, a strongly expanded basal portion of the amphithecial cortex, and a primarily western North American montane distribution. However, L. wetmorei cannot be mistaken for Lecanora indigoana because of the former’s complete lack of a thallus (Śliwa 2007; examination of the holotype, C. Wetmore 16568, MIN! [MIN 722988]). Additionally, L. wetmorei has entire (never occasionally incised) disc margins, and for the most part, a taller amphithecium.	en	Manzitto-Tripp, Erin A., Watts, Jacob L. (2025): The Thin Horizon of a Plan is Almost Clear: Towards a Lichen Biodiversity Inventory of the Southern Rocky Mountains, USA. Phytotaxa 712 (3): 207-229, DOI: 10.11646/phytotaxa.712.3.1, URL: https://doi.org/10.11646/phytotaxa.712.3.1
03ED879C762F90638083460F7A1B93AF.taxon	description	As in Tripp et al. (2019), we here opt to place the new species within a broadly defined concept of the genus Lecanora vs. the alternative, more narrowed circumscription of the lineage, i. e., Myriolecis Clements (Zhao et al. 2016), which has been used recently to refer to members of the Lecanora dispersa (Pers.) Röhl. group to which the new species belongs. We refrain from treatment of L. indigoana in other genera until a more stable classification (i. e., one in which the recognition of multiple segregate genera no longer renders Lecanora massively non-monophyletic) can be put forward. Conservation Assessment. Based on current knowledge, Lecanora indigoana is here assessed as Critically Endangered (CR) under criterion D of the IUCN Red List (IUCN 2024), which was invoked as a result of only two known populations consisting of a total of two mature individuals each. Additional Specimens Examined. USA, Colorado, Delta County. Gunnison National Forest, CR 265, lower montane stand of Populus tremuloides and Picea pungens, corticolous on P. pungens, 8710 ft., 39.124 568 - 107.54828, 13 May 2024, J. Watts & E. Manzitto-Tripp 1496 (COLO!). Pitkin County. White River National Forest, Placita Trailhead, semi-arid, west-facing slope dominated by Quercus gambellii Liebm. and Populus tremuloides, corticolous on P. tremuloides, 7586 ft., 39.135 45 - 107.26985, 13 May 2024 (E. Manzitto-Tripp & J. Watts 10436 (COLO!).	en	Manzitto-Tripp, Erin A., Watts, Jacob L. (2025): The Thin Horizon of a Plan is Almost Clear: Towards a Lichen Biodiversity Inventory of the Southern Rocky Mountains, USA. Phytotaxa 712 (3): 207-229, DOI: 10.11646/phytotaxa.712.3.1, URL: https://doi.org/10.11646/phytotaxa.712.3.1
03ED879C762A906E808341A37CCA951F.taxon	materials_examined	TYPE. USA. Colorado. Saguache County, BLM land east of Cochetopa Pass, Sheep Creek Road (BLM 5252 N), high elevation sage steppe dissected by mesic, boulder-rich ravines with Artemesia spp., Abies lasiocarpa, Populus tremuloides, Rosa woodsii, and Pinus aristata, saxicolous on rocks in ravine, 9086 ft. elev., 38.199 28, - 106.49064, 17 July 2024, E. Manzitto-Tripp & J. Watts 10,998 (Holotype: COLO!; Isotype: KANU!). Figures 3 – 4 & 7. Mycobank #. 860002	en	Manzitto-Tripp, Erin A., Watts, Jacob L. (2025): The Thin Horizon of a Plan is Almost Clear: Towards a Lichen Biodiversity Inventory of the Southern Rocky Mountains, USA. Phytotaxa 712 (3): 207-229, DOI: 10.11646/phytotaxa.712.3.1, URL: https://doi.org/10.11646/phytotaxa.712.3.1
03ED879C762A906E808341A37CCA951F.taxon	description	Description. Thallus crustose, leprose, placodioid, with (usually) crisped margins forming a conspicuously raised lip that ascends upward, prominently above primary plane of thallus, very rarely with only somewhat raised margins that are not conspicuously crisped and raised, the lips and margins conspicuously yellow in color, central portions of thallus irregularly pigmented, ranging from yellowish gray to whitish gray. Lobes indistinct to distinct, when distinct, raised, yellowed, and 1 – 2 mm wide. Granules irregular to less commonly subglobose, mostly ecorticate (ecorticate portions extremely yellow), typically with short projecting hyphae, to sometimes pseudocorticate (these portions whitish gray), 50 – 110 μm in diameter. Hypothallus consisting of thick, white, protruding hyphae, these ca. 80 μm long, segmented and branching, 2.5 – 3.5 μm thick. Hypothallus bearing scattered, reddish-brown, morphologically highly differentiated shiny, prominent rhizohyphae, 3.0 – 3.5 μm thick, branched. Photobiont chlorococcoid, cells 7 – 12 μm in diameter.	en	Manzitto-Tripp, Erin A., Watts, Jacob L. (2025): The Thin Horizon of a Plan is Almost Clear: Towards a Lichen Biodiversity Inventory of the Southern Rocky Mountains, USA. Phytotaxa 712 (3): 207-229, DOI: 10.11646/phytotaxa.712.3.1, URL: https://doi.org/10.11646/phytotaxa.712.3.1
03ED879C762A906E808341A37CCA951F.taxon	etymology	Etymology. This new lichen species is named in honor of Emily Saliers of the long-time musical duo, Indigo Girls. Together with Amy Ray, Emily has worked tirelessly to advocate for environmental rights and to end destructive, industrial practices that are catastrophic to both biodiversity and human livelihood. She has been a vocal opponent of (and has helped to fundraise against) the Dakota Access, Keystone, and Enbridge Pipelines, which devastate river water quality, violate treaty rights of Native Nations, and pose major threats to riparian ecosystems and the peoples that depend on them. Emily’s music is rooted in intellectual curiosity, understanding, awareness, compassion, and reflection. Her songs have been a powerful catalyst to inspire social change, which is intimately linked and crucial to the preservation of our native ecosystems and their resident species. Emily’s music has kept us company over many years of fieldwork (and microscopy!) spent documenting and conserving the biodiversity that surrounds us. This new species reminds us of Emily because its striking yellow thallus is bright, lively, and conveys a warmness. Chemistry. Spot Tests. K + yellow, C-, KC-, P + orange to red, UV-. Thin Layer Chromatography: atranorin (major to trace or rarely absent), roccellic / angardianic (major to absent), pannaric acid 6 - methyl ester (major), pannaric acid (major), unknown dibenzofuran A, and + / - pannaric acid 2 - methyl ester (only 2 specimens).	en	Manzitto-Tripp, Erin A., Watts, Jacob L. (2025): The Thin Horizon of a Plan is Almost Clear: Towards a Lichen Biodiversity Inventory of the Southern Rocky Mountains, USA. Phytotaxa 712 (3): 207-229, DOI: 10.11646/phytotaxa.712.3.1, URL: https://doi.org/10.11646/phytotaxa.712.3.1
03ED879C762A906E808341A37CCA951F.taxon	distribution	Distribution. Lepraria saliersiae is known currently from 20 specimens deriving from 12 different counties, nine in Colorado (Boulder, Gunnison, Huerfano, Jefferson, Mineral, Otero, Park, Pitkin, Saguache, San Miguel) and three in New Mexico (Hidalgo, San Juan, Sandoval). Substrate & Habitat. The 20 collections of Lepraria saliersiae reported here were made primarily on rocks (or rarely overgrowing mosses in crevices) in sheltered habitats such as in micro-watersheds (i. e., less than 100 m wide) and rock crevices. The new species seems to have an affinity in particular for soft rocks such as sandstone. Lepraria saliersiae has been found growing in a variety of low to mid elevation habitats of the SoRo ranging from mixed-grass prairie ecosystems to high elevation sage-steppe and upper montane forests ranging between ~ 4,400 – 10,500 ft. elev. We expect that continued surveys of the southern Rocky Mountain lichen biota (coupled with new herbarium studies of existing materials) will continue to expand the known range of this remarkable species. Notes. In North America, Lepraria saliersiae (Figure 4) is a charismatic component of the leprose crust lichen community of the southern Rocky Mountains, distinctive by its placodioid thallus with crisped margins that form conspicuously raised lips that ascend clearly above primary plane of the thallus (i. e. normandinoides - type sensu Lendemer [2013]), its remarkable yellow pigmentation that accentuates various portions of the thallus but especially the margins, its irregularly shaped granules that vary from predominantly ecorticate with short projecting hyphae to occasionally pseudocorticate, its hypothallus that bears reddish-brown rhizohyphae that are long, branched, shiny, and reddish-brown in color, and its nearly consistent production of atranorin (in addition to other compounds). In the southern Rocky Mountains, Lepraria saliersiae has historically likely been to be confused for L. vouauxii (Hue) R. C. Harris, but that species lacks defined margins (i. e., has an aggregate-type thallus), has non-pigmented rhizohypae (where present), is chemically variable but most frequently lacks atranorin, oftentimes occurs on bark (both of which are the case for the type, L. Vouaux s. n. in Claudel, Claudel & Harmand, Lich. Gall. Praec. Exs. No. 300, H- 9504035, isolectotype [photo!]; TLC = methyl pannaric acid complex only), and is phylogenetically more distantly related to Lepraria saliersiae (Figure 3; Laundon 1989; Lendemer 2013). Lendemer (2013) employs a broad species concept for L. vouauxii in North America to include many saxicolous specimens from western North America that we here treat as L. saliersiae. Consistent with the type specimen (cited above), the current contribution adopts a narrower concept of L. vouauxii to only include those specimens that occur primarily on bark or mosses and detritus over bark, lack atranorin, and have aggregate-type thalli. Based on current knowledge, we do not consider it yet known from Colorado and therefore exclude it from the key. The new species may also be confused L. membranacea (Dicks.) Vain., which has been variously treated as present either only in eastern North America (Lendemer 2013) or more widely recognized throughout much of North America (https: // lichenportal. org / portal /). In concordance with Lendemer (2013), it is likely that L. membranacea is largely or wholly restricted to eastern North America and absent from arid regions of western North America; we therefore do not currently recognize the species as occurring in Colorado and exclude it from the key. Lepraria saliersiae can, however, be differentiated from L. membranacea (J. Dickson s. n., BM, holotype [photo!]) because the latter, while placodioid, lacks crisped, raised margins (i. e. finkii - type sensu Lendemer [2013]), has unpigmented rhizohypae (where present), rarely produces atranorin, lacks metabolites in the methyl pannaric acid complex, and is phylogenetically more distantly related to Lepraria saliersiae (Figure 3; Laundon 1989; Lendemer 2013). We suspect that many specimens currently annotated as L. vouauxii or L. membranacea in arid, western North America likely belong to the new species: L. saliersiae. Lepraria diffusa (J. R. Laundon) Kukwa is another yellow, dibenzofuran-containing species reported from western North America (mostly from the Pacific Northwest and northern Rocky Mountains, but also from Colorado [e. g., E. Manzitto-Tripp, J. Watts, & S. Raynor 11818, E. Manzitto-Tripp & W. Manzitto-Tripp 10735, and J. Watts, E. Manzitto-Tripp, & S. Raynor 4214]) but it is easily differentiated from L. saliersiae by its aggregate-type thallus. Finally, the new species may be confused with Lepraria xerophila Tønsberg, but that is a strongly western maritime, terricolous species with exceptionally thick thalli that are uniformly whitish yellow (vs. bright yellow at the margins as in L. saliersiae) and often squamulose so to appear similar to a Cladonia. Additionally, L. xerophila is distinct chemically from L. saliersiae as it lacks pannaric acid as a major metabolite and produces porphyrilic acid (and related compounds) and rangiformic acid and / or roccellic / angardianic as fatty acids rather than only roccellic / angardianic as in L. saliersiae. In instances where thalli of species of Lepraria are poorly developed and / or immature, TLC is highly recommended to help aid in their identification and to differentiate the new species from congeners. In Colorado, other species of Leparia with placodioid thalli include L. eburnea J. R. Laundon, L. finkii (B. de Lesd.) R. C. Harris, and L. normandinoides Lendemer & R. C. Harris. Lepraria eburnea is similarly shades of yellow to green but lacks a crisped margin and produces alectorialic, barbatolic, and sometimes protocetraric acid. Lepraria finkii can sometimes bear yellowish green granules but lacks a crisped margin and produces zeorin, stictic acid aggregate, and sometimes roccellic / angardianic acids. Lepraria normandinoides cannot be confused with Lepraria saliersiae as it is bluish white to gray in color and produces roccellic / angardianic acid, and sometimes protocetraric acid. Based on observations during recent field efforts, thallus morphology of Lepraria saliersiae appears to vary considerably with microclimatic conditions. In more sheltered situations over harder rocks and / or overgrowing cushion mosses, L. saliersiae tends to exhibit less conspicuously raised margins, smaller granules with less well-developed pseudocortices, and more uniformly greenish yellow thalli, thereby approaching the morphology of L. membranacea. In exposed microsites, L. saliersiae appears to be restricted to vertical to overhung faces of soft sandstones or the soil-rock interfaces where it develops strongly crisped margins, irregular granules with pseudocortices, and distinctly bicolored thalli with bright yellow margins and irregularly / patchily whitish gray centers, in some ways approaching the morphology of L. xerophila but never as thick, white, and squamulose as the latter. We have sequenced a range of these moprhologies and all were resolved as reciprocally monophyletic, with strong support (100 % BS; Figure 3). The chemistry of Lepraria saliersiae is notable because it invariably produces a presumably undescribed dibenzofuran (unknown dibenzofuran A in TLC section) as a major metabolite. Unknown dibenzofuran A is characterized by an Rf value of ~ 15 in solvent A, its lack of charring after sulfuric acid and application of heat, and its longwave UV (greenish yellow) fluorescence before charring (UV- after charring). Unknown dibenzofuran A may be related to the dibenzofuran methyl porphyrilate, as this chemical species also does not char, but the latter compound has an Rf value of 23 and fluoresces purple under longwave UV. Our phylogenetic analyses placed our five accessions of Lepraria saliersiae as reciprocally monophyletic with strong support (100 % BS; Figure 3). Lepraria saliersiae was resolved, also with strong support (93 %), as sister to a clade (93 % BS) containing collections of L. sipmaniana (Kümmerl. & Leuckert) Kukwa and L. cryptovouauxii Kukwa from Bolivia (Figure 3). Indeed, L. sipmaniana and L. cryptovouauxii are similarly placodioid, yellow in color, and produce dibenzofurans, like Lepraria saliersiae (Laundon 1989; Flakus et al. 2011; Guzow-Krzemińska et al. 2019). However, Lepraria saliersiae can be readily differentiated from L. cryptovouauxii in having conspicuous, crisped lip-like margins, in producing pannaric acid 2 - methyl ester, by its branching rhizohyphae, in never producing anthraquinones, and by the single nucleotide polymorphisms present in the nrITS DNA alignment. Lepraria saliersiae can be readily differentiated from L. sipmaniana in its granules with hyphal projections, its production of atranorin and pannaric acid 2 - methyl ester (trace) (and spot tests, i. e., C-), and its typically smaller granules. So far as known, L. cryptovouauxii and L. sipmaniana have not yet been reported from North America.	en	Manzitto-Tripp, Erin A., Watts, Jacob L. (2025): The Thin Horizon of a Plan is Almost Clear: Towards a Lichen Biodiversity Inventory of the Southern Rocky Mountains, USA. Phytotaxa 712 (3): 207-229, DOI: 10.11646/phytotaxa.712.3.1, URL: https://doi.org/10.11646/phytotaxa.712.3.1
03ED879C762A906E808341A37CCA951F.taxon	materials_examined	Conservation Assessment. Based on our current knowledge and field exploration throughout the southern Rocky Mountains, Lepraria saliersiae is currently assessed as Endangered (EN) under criterion D of the IUCN Red List (IUCN 2024), which was invoked as a result of the total known population size of the species being less than 250 individuals. Lepraria saliersiae appears to be relatively widespread in Colorado based on the authors’ collections. In addition to new fieldwork throughout western North America, further study of herbarium materials currently ascribed to “ Lepraria vouauxii ” and “ Lepraria membranacea ” should be examined to determine whether these specimens may represent additional material of the new species, which may alter this preliminary IUCN assessment. Additional Specimens Examined. USA. Colorado. Boulder County. City of Boulder Open Space & Mountain Parks, outcropping between S. Cherryvale Rd. and Marshall Drive, mixed-grass prairie and Cercocarpus montanus, Pinus ponderosa, Prunus virginiana, Ribes cereum, saxicolous at base of vertical outcropping of soft Laramie Sandstone, 39.962 026, - 105.21188, 5650 ft. elev., 14 April 2025, J. Watts 3450 (COLO!). Gunnison County. Gunnison National Forest, outcropping just south of McClure Pass, north-facing slope of Douglas Fir, Spruce, Fir, and Aspen, geology of coarse-grained sandstone, saxicolous, 39.126 761, - 107.288151, 8864 ft. elev., 11 June 2025, E. Manzitto-Tripp & J. Watts 11649 (COLO!). Gunnison National Forest, Raggeds Wilderness, Dark Canyon Trail along Anthracite Creek north of Prospect Point, south-facing outcropping of Rollins Sandstone of the Mesaverde Formation amongst Juniperus scopularum and Quercus gambelii, saxicolous in cracks, 38.960 708, - 107.256943, 6940 ft. elev., 10 June 2025, J. Watts & E. Manzitto-Tripp 3902 (COLO!). Huerfano County. Southern extent of San Isabel National Forest just west of CR 630, pinyon-juniper woodland with the occasional Ponderosa Pine over soft sandstone, saxicolous in cracks, 37.895 97, - 105.15325, 8406 ft. elev., 24 May 2025, E. Manzitto-Tripp & J. Watts 11547 (COLO!); J. Watts & E. Manzitto-Tripp 3749 (COLO!). San Isabel National Forest, Spanish Peaks Wilderness, Wahatoya Creek, mature, open canopy, humid, riparian middle montane forest with a lush herbaceous layer, Abies concolor, Pseudostuga menziesii, and Populus tremuloides dominant, Picea engelmannii and Populus angustifolia occasional, geology of intermixed Cuchara sandstone outcroppings and hard intrusive igneous outwashed boulders, saxicolous, 37.401 99, - 104.95368, 9058 ft. elev., 24 May 2025, E. Manzitto-Tripp & J. Watts 11572 (COLO!); J. Watts & E. Manzitto-Tripp 3780 (COLO!). Jefferson County. South Valley Park, inclined Pinus ponderosa savanna on Front Range cuesta, saxicolous on vertical soft Lyons sandstone near ephemeral stream, 39.558 099, - 105.139437, 6,037 ft. elev., 4 January 2025, J. Watts & R. Wilkens 3095 (COLO!). La Plata County. San Juan National Forest, Weminuche Wilderness, Vallecito Creek Trail (529) between the first bridge and the trailhead along the west banks of Vallecito Creek, a montane forest of Pseudostuga menziesii, Pinus ponderosa, and the occassional Picea engelmannii, Pinus flexilis, and Abies concolor, understory lush with Rubus spp., Lonicera involucrata, Prunus americana, and Quercus gambelii, abundant granitic cliffs and outcroppings, saxicolous, 37.510 638, - 107.53618, 8353 ft. elev., 19 June 2025, E. Manzitto-Tripp & J. Watts 11782 (COLO!). Mineral County. Rio Grande National Forest, La Garita Wilderness, northwest facing slopes between Wheeler NM Trail and East Bellows Creek, a spruce bark-beetle damaged forest with Dasiphora fruticosa as the dominant shrub, large north-facing outcrops south of river, geology of intrusive igneous rocks, saxicolous, 37.831 773, - 106.732012, 10483 ft. elev., 17 June 2025, E. Manzitto-Tripp & J. Watts 11699 (COLO!). San Juan National Forest, vicinity of Treasure Falls, west-facing gulch of mixed montane forest of Abies concolor, Picea engelmannii, Pseudostuga menziesii, and Populus tremuloides, understory of Amelchier alnifolia, Quercus gambelii, and Cornus sericea, muscicolous over rock in crevice, 37.442 226, - 106.875829, 8182 ft. elev., 18 June 2025, J. Watts & E. Manzitto-Tripp 4022 (COLO!). Otero County. Comanche National Grassland, open wash dominated by Juniperus and sheltered outcrops, saxicolous at base of rocks, 37.652 519, - 103.570902, 4,384 ft. elev., 27 March 2025, S. Raynor & J. Watts 6100 (COLO!). Park County. Eagle Rock Ranch, rocky hillside with large and Artemesia dracunculus, Mertensia lanceolata, Ribes cereum, and Muhlenbergia montana, saxicolous and on moss under rock, 39.243 711, - 105.644322, 9,000 ft. elev., 14 July 2023, T. Cook. s. n. (COLO!). Pitkin County. White River National Forest, South Fork Fryingpan River, ~ 4 aerial miles southeast of Norrie Colony, lower subalpine forest of Spruce and Fir with the occasional Douglas Fir, Lycopodium annotinum in understory with abundant large granitic boulders densely covered in mosses and lichens, saxicolous, 39.279 27, - 106.61148, 9328 ft. elev., 12 June 2025, E. Manzitto-Tripp & J. Watts 11681 (COLO!); J. Watts & E. Manzitto-Tripp 3978 (COLO!). San Miguel County. West-facing slope east of Fall Creek from Fall Creek Recreation Site, montane forest with Pseudotsuga menziesii and Picea englemannii and steep canyon wall of crumbling Dolores Formation sandstone, saxicolous in rock crevice, 37.978 955, - 108.0298, 7,697 ft. elev., 24 July 2024, J. Watts & S. Raynor 2299 (COLO!). New Mexico. Hidalgo County. Granite Pass, saxicolous in crack in boulder, 26 April 1992, 5,000 ft., R. Worthington 20667 (COLO!). San Juan County. S side of Chaco Wash across from Casa Chiquita ruins, on soil and among mosses, 6,200 ft., 7 August 1979, L. Sigal & T. Nash III 16,303 (COLO!). Sandoval Country. Bandelier National Monument, travel from Saint Peters Dome to breaks of Capulin Canyon, steep, moist, north-facing slopes with Pseudotsuga menziesii, Pinus ponderosa, and Pinus strobiformis, 6,894 ft., 11 June 1980, W. Weber & T. Kelso s. n. (COLO!).	en	Manzitto-Tripp, Erin A., Watts, Jacob L. (2025): The Thin Horizon of a Plan is Almost Clear: Towards a Lichen Biodiversity Inventory of the Southern Rocky Mountains, USA. Phytotaxa 712 (3): 207-229, DOI: 10.11646/phytotaxa.712.3.1, URL: https://doi.org/10.11646/phytotaxa.712.3.1
03ED879C7627906A808347317B309423.taxon	materials_examined	TYPE: USA. Colorado. Eagle County. White River National Forest, Holy Cross Wilderness. Northwest-facing slopes just above the middle fork of Homeskate Creek amongst a dense lower subalpine forest of Picea engelmanii and Pinus contorta. Saxicolous and muscicolous on large, shaded vertical rock faces, locally abundant, 9492 ft. elevation, 39.387 005, - 106.451006, 16 July 2024, J. Watts & E. Manzitto-Tripp 2235 (Holotype: COLO!; Isotypes: ASU!, BYU!, KANU!, NY!). Figures 5 – 7. Mycobank #: 860003	en	Manzitto-Tripp, Erin A., Watts, Jacob L. (2025): The Thin Horizon of a Plan is Almost Clear: Towards a Lichen Biodiversity Inventory of the Southern Rocky Mountains, USA. Phytotaxa 712 (3): 207-229, DOI: 10.11646/phytotaxa.712.3.1, URL: https://doi.org/10.11646/phytotaxa.712.3.1
03ED879C7627906A808347317B309423.taxon	description	Description. Thallus crustose, continuous, thin, smooth, shiny where corticate, becoming ecorticate near regions of isidia development, whitish gray. Prothallus absent. Upper cortex thin, 18 – 48 μm thick, prosoplectenchymatous. Algal layer interrupted and irregular, up to 25 – 50 μm thick. Medulla prominent, 74 – 126 μm. Lower surface consisting of single layer of parallel-oriented hyphae, shiny, whitish gray, lacking attachment structures. Isidia pale yellow to grayish white and slightly lighter in color than surrounding thallus, coralloid, solid, unbranched or branched primarily once towards apex giving a forked appearance, occasionally with additional branching, oftentimes very dense and covering majority of surface of thallus on older thalli, but occurring isolated and dispersed on younger thalli, 125 – 187 μm thick and up to 750 μm long. Apothecia and associated sexual reproductive structures unknown. Photobiont chlorococcoid, cells 9 – 16 μm in diameter.	en	Manzitto-Tripp, Erin A., Watts, Jacob L. (2025): The Thin Horizon of a Plan is Almost Clear: Towards a Lichen Biodiversity Inventory of the Southern Rocky Mountains, USA. Phytotaxa 712 (3): 207-229, DOI: 10.11646/phytotaxa.712.3.1, URL: https://doi.org/10.11646/phytotaxa.712.3.1
03ED879C7627906A808347317B309423.taxon	etymology	Etymology. This new lichen species is named in honor of Amy Ray of the long-time musical duo, Indigo Girls. Together with Emily Saliers, Amy has been an indefatigable advocate for environmental protection and social justice. She (along with Emily and Winona LaDuke) co-founded the non-profit organization Honor the Earth, which works to promote education and raise awareness of environmental issues impacting indigenous communities. For numerous years, Amy has campaigned to help end nuclear waste dumping on Native American reservations and, together with Emily, has long integrated activism into her tours. Amy’s music is rooted in empathy, justice, wit, and equality, especially equal pay for women and other social rights that are inextricably linked to ecological health. Her songs have kept us company over many years spent understanding and describing lichen biodiversity; they have furthermore inspired much of our own scientific activism to help end repressive behaviors by governments and industries that do not serve the interests of our ecosystems nor human livelihood. This new species reminds us of Amy because its yellow isidia are radiant and full of life. It’s UV + orange reaction further reminds us that it is rather dynamic on the inside, too. Chemistry. Spot Tests: K + pale yellow to K-, C + orange to C-, KC + orange, P-, UV + orange (thallus and isidia). Thin Layer Chromatography: thiopaninic acid (major), atranorin (minor), unknown lichexanthone.	en	Manzitto-Tripp, Erin A., Watts, Jacob L. (2025): The Thin Horizon of a Plan is Almost Clear: Towards a Lichen Biodiversity Inventory of the Southern Rocky Mountains, USA. Phytotaxa 712 (3): 207-229, DOI: 10.11646/phytotaxa.712.3.1, URL: https://doi.org/10.11646/phytotaxa.712.3.1
03ED879C7627906A808347317B309423.taxon	distribution	Distribution. So far as currently understood, Pertusaria rayana is restricted to the Sawatch and San Juan Mountain ranges of Colorado where it is known only from two locations in two watersheds: Homeskate Creek immediately below Homeskate Reservoir and Vallecito Creek above Vallecito Reservoir. It is likely to be discovered elsewhere in comparable habitats, as future fieldwork to inventory the lichens of the southern Rocky Mountains continues. Substrate & Habitat. Pertusaria rayana grows directly over rocks or on mosses over rocks. It is thus far known to be restricted to vertical or slightly overhung rock faces in lower subalpine / upper montane forests proximal to creeks, between ~ 8,700 – 10,000 ft. elev. It has been collected associated with other sterile crustose lichens that occur in rich, riparian communities including trees draped abundantly with species of Bryoria Brodo & D. Hawksw. and Usnea Dill. ex Adans. Thus, the new species has an affinity to high humidity environments wherein valley fog likely commonly accumulates. The abundant, long isidia of the species likely represent a dual adaptation for asexual reproduction and fog capture as in the “ Cloud Lichens ” Niebla Rundel & Bowler, and other fruticose genera associated with foggy habitats (Stanton & Horn 2013). Notes. Pertusaria rayana (Figure 6) is a charismatic and easily recognizable species in Colorado by its pale yellow, dense, long, and coralloid isidia. The isidia of Pertusaria rayana are more yellow than the underlying thallus as a function of uneven pigment distribution, a phenomenon also characteristic for Lepraria saliersiae wherein the margins are far more pigmented than central portions of the thallus. Of isidiate Pertusaria in North America, Pertusaria rayana is readily differentiable by its substrate and chemistry, making it difficult to confuse for any congeneric species. Chemically, the most similar species is P. flavocorallina Coppins & Muhr, however that species lacks atranorin and has a K + violet pigment at the apices of its isidia (Gilbert & Coppins 1992). Furthermore, P. flavocaroallina is known from maritime rather than continental habitats. Additional features that help differentiate Pertusaria rayana from other isidiate species in western North America can be found in the key below (Part 2). It is possible the new species could be confused for a few other isidiate crustose lichens in other genera. Namely, some could confuse Pertusaria rayana for Loxosporopsis corallifera Brodo, Henssen & Imshaug, which differs by its UV + white reaction owing to the presence of divaricatic acid in the thallus, its heavily contorted isidia, and its corticolous habit (Brodo & Henssen 1995). Lepra corallina (L.) Hafellner, a primarily European species, is similarly saxicolous on vertical rock faces like Pertusaria rayana, but the former produces thamnolic acid and is therefore P + yellow-orange and UV- (Tønsberg 1992). Our phylogenetic analyses strongly support the reciprocal monophyly of our two accessions of Pertusaria rayana (99 % BS). The clade containing both accessions of the new species was resolved as sister to P. sommerfeltii (Flörke ex Sommerf.) Fr., which is a widespread, sexually reproducing species, but without support. Conservation Assessment. Pertusaria rayana is here assessed as Critically Endangered (CR) under IUCN criterion D because of its highly restricted occurrence in humid, riparian upper montane / lower subalpine forests where only ~ 10 mature individuals have been observed, making the estimated total population size fewer than 50 individuals. Although future fieldwork will surely result in the discovery of additional populations of this remarkable new species, it nonetheless is likely to be rare to very rare, as the authors have searched numerous other watersheds (with seemingly suitable habitat) for individuals, but without success.	en	Manzitto-Tripp, Erin A., Watts, Jacob L. (2025): The Thin Horizon of a Plan is Almost Clear: Towards a Lichen Biodiversity Inventory of the Southern Rocky Mountains, USA. Phytotaxa 712 (3): 207-229, DOI: 10.11646/phytotaxa.712.3.1, URL: https://doi.org/10.11646/phytotaxa.712.3.1
03ED879C7627906A808347317B309423.taxon	description	Additional Specimens Examined. USA. Colorado. Eagle County. White River National Forest, Holy Cross Wilderness, middle fork of Homeskate Creek, rich, north-facing slopes amongst subalpine forest dominated by Abies lasiocarpa and Populus tremuloides, saxicolous on shaded rocks, 9796 ft. elev., 39.381 02 - 106.45019, E. Manzitto-Tripp 11,300 (COLO!). White River National Forest, Holy Cross Wilderness, middle fork of Homeskate Creek, rich, north-facing slopes amongst subalpine forest dominated by Abies lasiocarpa and Populus tremuloides, 39.388 01 - 106.449 80, 9,441 ft. elev. E. Manzitto-Tripp 11,302 (COLO!). La Plata County. San Juan National Forest, Weminuche Wilderness, Vallecito Creek Trail (529) between the second and first bridges along east banks of Vallecito Creek, spruce bark beetle-damaged montane forest in a large valley with abundant granitic cliffs, canopy of mostly dead Picea engelmannii, Pseudostuga menziesii, and the occasional Abies concolor, understory lush with Rubus spp., Lonicera involucrata, Prunus americana, and Quercus gambelii, muscicolous over nearly vertical rock ~ 10 m above creek, 37.540 005, - 107.523342, 8705 ft. elev., J. Watts & E. Manzitto-Tripp 4103 (COLO!).	en	Manzitto-Tripp, Erin A., Watts, Jacob L. (2025): The Thin Horizon of a Plan is Almost Clear: Towards a Lichen Biodiversity Inventory of the Southern Rocky Mountains, USA. Phytotaxa 712 (3): 207-229, DOI: 10.11646/phytotaxa.712.3.1, URL: https://doi.org/10.11646/phytotaxa.712.3.1
