taxonID	type	description	language	source
039387A4FFE2646A2BE042C9FD95F2C3.taxon	diagnosis	Diagnosis: — Thallus foliose, irregularly orbicular, of narrow, ± convex, radiating, lobes brown to cream-colored, K + yellow, adnate, lacking a lower cortex, rhizines brown, often projecting beyond lobe margins, growing on rocks. It is most easily confused with Heterodermia japonica but differs by having narrower lobes, a discontinuous algal layer, and lacking japonene and related terpenes. It is reminiscent of Heterodermia speciosa and H. tremulans because of its bluish, granular soredia in labriform soralia, but lacking a lower cortex and having narrower lobes. It is distinct from H. chilensis (Kurok. 1962: 65) Swinscow & Krog (1976: 115) by its adnate growth form, dense rhizines, expanded and incised lobe apices, and lack of distinctly thickened, corticate margins of the lobe undersurface.	en	Watts, Jacob L., Raynor, Seth J., Manzitto-Tripp, Erin A. (2025): Character evolution in Heterodermia s. l. (Physciaceae; Caliciales) and two new species from the southern Rocky Mountains, USA. Phytotaxa 698 (2): 61-81, DOI: 10.11646/phytotaxa.698.2.1, URL: https://doi.org/10.11646/phytotaxa.698.2.1
039387A4FFE2646A2BE042C9FD95F2C3.taxon	materials_examined	TYPE: — USA, Colorado, Park Co., Eleven Mile Canyon Recreation Area. 38 ° 57 ’ 58.98 ” N, 105 ° 22 ’ 14.59 ” W, 2486 m elevation, on sloping boulders in a steep canyon forest dominated by Pseudotsuga menziesii, 22 August 2024, J. Watts 2552 (holotype, COLO!; isotype, NY!).	en	Watts, Jacob L., Raynor, Seth J., Manzitto-Tripp, Erin A. (2025): Character evolution in Heterodermia s. l. (Physciaceae; Caliciales) and two new species from the southern Rocky Mountains, USA. Phytotaxa 698 (2): 61-81, DOI: 10.11646/phytotaxa.698.2.1, URL: https://doi.org/10.11646/phytotaxa.698.2.1
039387A4FFE2646A2BE042C9FD95F2C3.taxon	description	Description: — Thallus foliose, orbicular to irregular, often small (~ 2.5 – 5 [– 8] cm in diameter), adnate. Lobes radiating, irregularly to ± sympodially branched, narrow ([0.5] – 0.7 – 1.1 mm broad), convex to flat, or rarely undulate, contiguous to imbricate. Lobe apices expanded (to 1.3 – 1.6 mm) and incised to radially branching. Upper surfaces dull, cream-colored to light grey, but often brown pigmented from light exposure. Maculae rarely present in low light. Lobe apices pruinose, rarely epruinose in low light. Upper cortices prosoplectenchymatous, of uneven thickness, (12 –) 25 – 75 (– 130) µm thick. Asexual lichenized propagules coarse soredia (45 – 65 µm in diameter) borne primarily on secondary lobes in terminal, ± labriform soralia, variable depending on the light environment; in low light, developing large, typical labriform soralia on undersurface of greatly expanded lobe apices, in high light, developing terminal small, ± labriform soralia with dark greyish-blue pigmented, coarsely granular soredia and the occasional small, laminal, round soralium in older parts. Algal layer discontinuous, interrupted by cortical intrusions, (25 –) 55 – 95 (– 120) µm thick. Algae trebouxoid, spherical, 10 – 16 µm in diameter. Medulla white, 67 – 205 µm thick, non-amyloid (I-). Lower surfaces arachnoid, dull, marginally white, becoming light brown centrally, developing a pseudocortex, rhizinate. Rhizines dense, marginal and often projecting beyond the lobe margin, concolorous with the thallus or brown, rarely becoming black, simple to irregularly branched, 1 – 2 (– 3) mm long, partially obscuring the lower surface centrally. Lower cortices absent from lobe apices, centrally developing a pseudocortex of ± conglutenated medullary cells, often impregnated with debris. Apothecia rare, only known from the type specimen; when present, lecanorine, sessile to substipitate, constricted at the base, to 1.5 mm in diameter. Thalline margins at first smooth, becoming partially sorediate. Disks brown, concave, epruinose. Asci narrowly clavate, 45 – 57 × 13 – 17 µm, 8 - spored. Ascospores brown, two-celled, Physcia-type, lumina angular, septa dark pigmented, apical walls thickened, one cell often larger than the other. (7 –) 8 – 12 × (16 –) 18 – 24 µm (n = 10). Epihymenium brown to reddish brown, K-, 3 – 9 µm thick, pigment inside and between paraphyses apices. Hymenium hyaline, 50 – 65 µm thick, I + blue. Paraphyses simple, unbranched, cylindrical, 2.5 – 3.5 µm thick at apex. Hypothecium hyaline, 25 – 65 µm thick. Proper exciples 12 – 25 µm thick, hyaline. Thalline margins 100 – 150 µm thick apically, corticate, cortex thicker basally, 30 – 150 µm thick. Pycnidia rare, immersed. Ostioles light brown to black. Conidia bacilliform, 3 – 5 × 1 µm. Spot tests: — Cortex, medulla, and lower surface: K + yellow, C-, KC- (remaining yellow), P- or P + pastel yellow. Lower surface pigment K-. Secondary Metabolites: — Atranorin (major) and zeorin (major), and rarely salazinic acid (trace). Substrate and Ecology: — Saxicolous and muscicolous on vertical to sloping, usually mossy and mesic to semimesic rock faces in montane to lower subalpine forests between ~ 6000 ft. and ~ 10,500 ft. Most abundant on north-facing slopes just above rivers and cliff bases at ~ 8500 ft. elevation. One specimen known from bark (W. Weber & L. Viereck s. n., COLO – S 7181). World distribution: — Infrequent to rare in the southern Rocky Mountains of Colorado with a disjunct locality in Alaska suggesting a much broader distribution, perhaps throughout the northern Rocky Mountains as well.	en	Watts, Jacob L., Raynor, Seth J., Manzitto-Tripp, Erin A. (2025): Character evolution in Heterodermia s. l. (Physciaceae; Caliciales) and two new species from the southern Rocky Mountains, USA. Phytotaxa 698 (2): 61-81, DOI: 10.11646/phytotaxa.698.2.1, URL: https://doi.org/10.11646/phytotaxa.698.2.1
039387A4FFE2646A2BE042C9FD95F2C3.taxon	etymology	Etymology: — The epithet ‘ caesiosora ’ refers to the bluish grey soredia of the species. Conservation Assessment: — Heterodermia caesiosora is preliminarily assessed as Critically Endangered (CR) based on IUCN criterion D, as fewer than 50 mature individuals are estimated to occur in the wild. We are so far aware of 7 historical and 13 modern (total 20) specimens that can be attributed to H. caesiosora. In all modern collections made by the authors, only one mature individual was observed; however, we expect the species to be overlooked / undercollected are thereby double our estimate of the number of mature individuals to 40. Notes: — Heterodermia caesiosora is characterized by its narrow, ± convex, K + yellow lobes that are adnate and lack a lower cortex, its bluish grey labriform soralia terminal on secondary lobes, its brown rhizines which often project beyond the lobe margins, and its small spores. Heterodermia japonica, a pantropical species, is similar in its lack of lower cortex and labriform soralia but that species has black, ± squarrose rhizines that are never visible from above, a continuous algal layer and uniformly thick upper cortex, and japonene and related terpenes. Heterodermia chilensis, a species of coastal Chile, has labriform soralia and an interrupted algal layer, but this species exhibits lobes that are marginally discrete and dichotomously branching, the apices of which are entire, not incised as in H. caesiosora. Heterodermoa galactophylla (Tuck. 1848: 224) W. L. Culb. (1967: 482) differs by its subascending lobe apices which bear labriform soralia; most primary lobe apices of H. caesiosora are esorediate, the soralia concentrated to secondary lobes. Heterodermia hypocaesia (Yasuda in Räsänen 1940: 139) D. D. Awasthi (1973: 113), a primarily southern hemisphere species, also lacks a lower cortex but has upturned, labriform soralia but differs in its yellowish lower surface, the regular presence of salazinic acid in high concentrations, and much larger ascospores. A few specimens of Heterodermia caesiosora were discovered in the COLO herbarium misidentified as H. speciosa and H. tremulans, both of which are superficially similar but are distinctly corticate underneath. Heterodermia caesiosora is additionally separated from these species by its discontinuous algal layer and smaller spores — these smaller than most species of Heterodermia. This misidentification is likely due to historical confusion surrounding the differences between cortex and pseudocortex. We expect further annotation of specimens from western NA will uncover more populations of H. caesiosora. Close examination of specimens in this complex from eastern NA may reveal further diversity in the group as the two treatments of Heterodermia for this area disagree on the identity of NA material as either H. tremulans (Culberson 1966), or H. speciosa (Lendemer 2009) and note extensive variation in the degree of development in the lower cortex (Lendemer 2009). Selected Specimens Examined: — UNITED STATES. Alaska: Denali Boro., McKinley River, Denali National Park and Preserve, 548 m, 63.4167, - 150.917, 1 August 1956, W. Weber & L. Viereck s. n., (COLO-S 7181). Colorado: Boulder Co., Bear Peak, Boulder Open Space and Mountain Parks, 2415 m, 39.962453, - 105.295841, 19 October 2023, J. Watts 768, (COLO). Eagle Co., Homeskate Creek, Holy Cross Wilderness, 2893 m, 39.387005, - 106.451006, 16 July 2024, J. Watts 2240, (COLO). Hinsdale Co., Vallecito Creek, 2741 m, 37.56836, - 107.521687, 26 November 1977, R. Rosentreter CO- 29, (COLO-L 95045). Jefferson Co., Northeast face of Green Mountain, Pike National Forest, 2624 m, 23 May 2024, J. Watts 1663, (COLO). Larimer Co., Dadd Gulch Trail just south of Cache la Poudre River, Roosevelt National Forest, 2499 m, 40.67759, - 105.558456, 11 May 2024, J. Watts 1423, (COLO). Pitkin Co., Lost Man Campground, Roaring Fork River, 3217 m, 39.119651, - 106.624281, 30 July 2024, J. Watts & Ella Henry 2449, (COLO). Teller Co., Raspberry Mountain, Pike National Forest, 3076 m, 38.885809, - 105.127882, 5 May 2024, J. Watts & S. Raynor 1392, (COLO).	en	Watts, Jacob L., Raynor, Seth J., Manzitto-Tripp, Erin A. (2025): Character evolution in Heterodermia s. l. (Physciaceae; Caliciales) and two new species from the southern Rocky Mountains, USA. Phytotaxa 698 (2): 61-81, DOI: 10.11646/phytotaxa.698.2.1, URL: https://doi.org/10.11646/phytotaxa.698.2.1
039387A4FFE764682BE04677FEB5F462.taxon	diagnosis	Diagnosis: — Thallus foliose, white to cream-colored, K + yellow, adnate, lacking a lower cortex, irregularly orbicular, growing on rocks. Distinct from its close relative, Heterodermia squamulosa, in its production of abundant and morphologically variable reproductive propagules ranging from soredia, these sometimes, with age, developing a cortex, to phyllidia. Other species produce phyllidia which can disintegrate into soredia, but Heterodermia exuberans is unique in producing both soredia and phyllidia concomitantly.	en	Watts, Jacob L., Raynor, Seth J., Manzitto-Tripp, Erin A. (2025): Character evolution in Heterodermia s. l. (Physciaceae; Caliciales) and two new species from the southern Rocky Mountains, USA. Phytotaxa 698 (2): 61-81, DOI: 10.11646/phytotaxa.698.2.1, URL: https://doi.org/10.11646/phytotaxa.698.2.1
039387A4FFE764682BE04677FEB5F462.taxon	materials_examined	TYPE: — USA, Colorado, Jefferson Co., Pike National Forest, northeast face of Green Mountain, 39 ° 19 ’ 11.71 ” N, 105 ° 17 ’ 52.33 ” W, 2624 m elevation, abundant at base of large granitic cliff in north-facing mixed montane conifer forest, 23 May 2024, J. Watts 1659 (holotype, COLO!; isotype, NY!).	en	Watts, Jacob L., Raynor, Seth J., Manzitto-Tripp, Erin A. (2025): Character evolution in Heterodermia s. l. (Physciaceae; Caliciales) and two new species from the southern Rocky Mountains, USA. Phytotaxa 698 (2): 61-81, DOI: 10.11646/phytotaxa.698.2.1, URL: https://doi.org/10.11646/phytotaxa.698.2.1
039387A4FFE764682BE04677FEB5F462.taxon	description	Description: — Thallus foliose, orbicular to irregular, becoming quite large (up to 12 cm in diameter), adnate. Thallus tightly adnate centrally, peripheral lobes loosely adnate; sometimes forming vertical tiers of decumbent / ascending lobes. Lobes radiating, irregularly to ± sympodially branched, broad ([0.8 –] – 1 – 2.5 – [– 3] mm across), flat to undulate, rarely imbricate. Lobe apices crenate to incised, expanded, and downturned. Upper surfaces dull, cream-colored to light grey, sometimes light brown from light exposure or light blue in apical regions. Weak, round to irregularly elongate maculae often present. Lobe tips occasionally lightly pruinose. Upper cortices prosoplectenchymatous, of uneven thickness, (40 –) 50 – 105 (– 137) µm thick. Asexual lichenized propagules abundant and morphologically variable, ranging (on a single thallus) from soredia to isidioid soredia to dorsiventral phyllidia; primarily borne on underside of upturned lobe tips, also borne along lobe margins and laminal surfaces in occasional clusters, especially on older parts of the thallus. Large phyllidia dorsiventral and densely branched, erect and imbricate, sometimes entirely obscuring the center of the thallus, never breaking down into soredia. Algal layer uneven and discontinuous, (25 –) 35 – 55 µm thick. Algae trebouxoid, spherical, 10 – 15 µm in diameter. Medulla white, (60 –) 75 – 105 µm thick, amyloid (I + violet). Lower surfaces arachnoid, dull, marginally white and becoming ± canaliculate, dark purple or yellowish-brown centrally, rhizinate. Rhizines at first simple and marginal, white to light brown, later becoming black, squarrose, and confluent, obscuring the lower surface centrally. Lower cortices absent from margins, centrally developing a pseudocortex of ± darkened, ± conglutinated medullary cells, often impregnated with debris. Apothecia rare, when present, lecanorine, sessile to substipitate, constricted at the base, to 4 mm in diameter. Thalline margins at first smooth, becoming phyllidiate and finally sorediate. Disks concave, dark brown, epruinose. Asci narrowly clavate, 30 – 35 × 90 – 100 µm at maturity; slow to develop and containing hyaline, immature spores in young apothecia, 8 - spored. Ascospores brown, two-celled, Pachysporaria-type, lumina rounded-angular, septa dark pigmented, lateral and apical walls thickened. (30 –) 32 – 37 (– 41) × (14 –) 15 – 17 µm (n = 10). Epihymenium brown to reddish brown, K-, 15 – 29 µm thick, pigment inside and between paraphyses apices. Hymenium hyaline, 78 – 105 µm thick, I + blue. Paraphyses simple, unbranched, cylindrical, 2.5 – 3.5 µm thick at apex. Hypothecium hyaline, 80 – 105 µm, thickest centrally. Proper exciples 22 – 35 µm, dark brown, appearing black in thick section. Thalline margins 115 – 200 µm thick apically, corticate, cortex 26 – 146 µm thick. Pycnidia infrequent, immersed. Ostioles light brown to black. Conidia bacilliform, 3 – 5 × 1 µm. Spot tests: — Cortex, medulla, and lower surface: K + yellow, C-, KC- (remaining yellow), P- or P + pastel yellow. Lower surface pigment K-. Secondary Metabolites: — Atranorin (major), zeorin (major), unknown terpene (subordinate and close to norstictic acid in solvent C, acid spray brown, aging purple, longwave UV orange), ± unknown fatty acid (same rf value as unknown terpene), ± leucotylin (minor). Substrate and Ecology: — Saxicolous and muscicolous on vertical to overhung, usually mossy and mesic to semimesic rock faces in montane to lower subalpine forests between ~ 6000 ft. and ~ 10,500 ft. Most abundant on north-facing slopes just above rivers and cliff bases ~ 8500 ft. where it often forms extensive colonies, likely from asexual reproduction. One specimen known from bark (S. Shushan s. n., COLO-S 5948) World distribution: — Common to infrequent in the mesic canyons and north-facing upper montane habitats of the Front Range of the southern Rocky Mountains with disjunct collections from upper montane-subalpine forests of Arizona.	en	Watts, Jacob L., Raynor, Seth J., Manzitto-Tripp, Erin A. (2025): Character evolution in Heterodermia s. l. (Physciaceae; Caliciales) and two new species from the southern Rocky Mountains, USA. Phytotaxa 698 (2): 61-81, DOI: 10.11646/phytotaxa.698.2.1, URL: https://doi.org/10.11646/phytotaxa.698.2.1
039387A4FFE764682BE04677FEB5F462.taxon	etymology	Etymology: — The epithet ‘ exuberans ’ is derived from the latin word for exuberant, describing its “ effusive and uninhibited ” production of asexual lichenized propagules in great abundance. These propagules are often so lavishly abundant as to obscure the thallus in older parts. We additionally chose this name for the way it makes the authors feel overflowing with joy to see healthy populations of this attractive lichen abounding in rich habitats where many other mysteries may also be found, if one looks closely. Conservation Assessment: — Heterodermia exuberans is preliminarily assessed as Endangered based on IUCN criterion D, as fewer than 250 mature individuals are estimated to occur in the wild. We are so far aware of 25 historical and 35 modern (total 60) specimens attributable to H. exuberans. At ~ 50 % of the localities visited by the authors, one mature individual was observed; at the other 50 %, two mature individuals were observed. Doubling the estimate due to the overlooked nature of the organism, we estimate a total population size of ~ 180 individuals. Notes: — Heterodermia exuberans is characterized by its diverse reproductive propagules, these fluidly developing and ranging in definition from soredia to isidioid soredia to finally dorsiventral phyllidia, a depsidone deficient chemistry, peripherally white, ecorticate lower surface, and saxicolous habit. In North America, it is most likely confused with its close relative, H. squamulosa, a corticolous species of the southern Appalachians, but this species can be differentiated by its corticolous habit and strictly marginal, strongly upturned phyllidia, these only occasionally disintegrating into soredia (Lendemer 2009). Heterodermia violostriata Elix (2011: 16) is a rare, corticolous species of Thailand and Australia that also has marginal and laminal phyllidia and a K + yellow cortex and medulla but differs in its greyish-violet streaked lower surface (similar pigments more continuous across the lower surface in H. exuberans) and larger spores with sporoblastidia. Heterodermia microphylla (Kurok. 1959: 123) Skorepa in Swinscow & Krog (1976: 139), a pantropical phyllidiate species, exhibits a similar propagule diversity to H. exuberans; however, in H. microphylla, propagules begin as distinctly corticate, dorsiventral phyllidia, only later becoming strongly dissected and disintegrating into soredia. Heterodermia appendiculata is supported as the closest relative to H. exuberans but differs primarily by its production of the depsidones norstictic and connorstictic acid. Likely because of its diversity of propagules, many specimens of this new species were found in the COLO herbarium, misidentified as Heterodermia casarettiana, H. japonica, or H. obscurata. These species are superficially similar in overall appearance to H. exuberans owing to their marginal soredia borne on the undersurface of upturned lobes, but differ ecologically, morphologically, and chemically. Heterodermia casarettiana differs by the (usual) presence of norstictic acid in the medulla, true soredia rather than phyllidia, primarily corticolous habit, and patches of pigment on the undersurface. In regard to the name H. casarettiana, there is some confusion about the distribution of pigments on the lower surface, and whether any differences in pigmentation distribution constitutes the designation of a new species. Because of this, Lendemer (2009) referred to eastern NA material of this species as H. casarettiana auct. Amer.; further investigation is required in this potential species complex. Another species that H. exuberans was often misidentified as in COLO is Heterodermia japonica, which differs by the presence of japonene, a continuous algal layer, and lack of phyllidia; however, in an unpublished correspondence (10 Dec. 1956) between William Weber and John Thomson, Thomson considered a specimen (S 5948; COLO) of H. exuberans to be a phyllidiate form of H. japonica. Finally, Heterodermia obscurata differs by having strictly soredia, a corticolous habit, and K + pigments on the lower surface. We expect further annotation of western North American material to fill out and / or expand the known biogeographic range of H. exuberans. Selected Specimens Examined: — UNITED STATES. Arizona: Apache Co., West side of Escudilla Mountain, 2987 m, 33.916996, - 109.111660, 21 May 1974, T. Nash 10724, (COLO-L 62125). Coconino Co., West side of San Franciso Peaks, 2682 m, 35.324977, - 111.711751, 14 July 1973, T. Nash 7510, (COLO-L 58147). Cochise Co., Trail from Rustler’s Park to Fly’s Peak, 2772 m, 31.878293, - 109.288749, 18 April 1957, W. Weber & S. Shushan s. n., (COLOS 8867). Colorado: Boulder Co., Boulder Canyon, Boulder Bowl, 2333 m, 39.998895, - 105.410657, 20 October 2024, J. Watts et al. 2848, (COLO). Custer Co., Hardscrabble Creek, Wet Mountains, 2455 m, 38.171836, - 105.175683, 14 May 1988, W. Weber & R. Wittman s. n., (COLO-L 83545). Douglas Co., Missouri Creek, Pike National Forest, 2315 m, 39.13572, - 105.10175, 24 May 2024, J. Watts 1696, (COLO). Hinsdale Co., Cebolla Creek Campground, 2865 m, 38.045902, - 107.099837, 29 July 1964, W. Weber s. n., (COLO-L 38440). Huerfano Co., South of La Veta along Huajatolla Creek, 2682 m, 37.360146, - 105.108568, 17 August 1955, S. Shushan s. n., (COLO-S 5948). Larimer Co., The Crags area of Twin Sisters Peaks, Arapaho National Forest, 2933 m, 40.306546, - 105.5249361, 1 June 2024, J. Watts & Edie Clark 1778, (COLO). Mineral Co., Big Meadows Road just above South Fork of the Rio Grande, 2737 m, 37.54997, - 106.78256, 16 May 2024, J. Watts, E. Manzitto-Tripp, & S. Raynor 1625, (COLO). Park Co., 11.3 mi east of Jefferson, on road to Lost Creek Wilderness, 3048 m, 39.280512, - 105.518077, 3 July 1955, S. Shushan s. n., (COLO-S 5712). Teller Co., North-west face of Mitre Peak just above Wilson Creek, 2082 m, 38.648993, - 105.215838, 4 May 2024, J. Watts & S. Raynor 1338, (COLO). New Mexico: San Miguel Co., Gallinas Canyon NW of Las Vegas, 2300 m, 35.718697, - 105.424593, 7 October 1973, W. Weber & G. Kunkel s. n., (COLO- L 57913).	en	Watts, Jacob L., Raynor, Seth J., Manzitto-Tripp, Erin A. (2025): Character evolution in Heterodermia s. l. (Physciaceae; Caliciales) and two new species from the southern Rocky Mountains, USA. Phytotaxa 698 (2): 61-81, DOI: 10.11646/phytotaxa.698.2.1, URL: https://doi.org/10.11646/phytotaxa.698.2.1
039387A4FFE764682BE04677FEB5F462.taxon	description	New Combination: — Below, we provide a new combination for a taxon that has not yet been treated in Heterodermia.	en	Watts, Jacob L., Raynor, Seth J., Manzitto-Tripp, Erin A. (2025): Character evolution in Heterodermia s. l. (Physciaceae; Caliciales) and two new species from the southern Rocky Mountains, USA. Phytotaxa 698 (2): 61-81, DOI: 10.11646/phytotaxa.698.2.1, URL: https://doi.org/10.11646/phytotaxa.698.2.1
