Assessed as Critically Endangered A2c; B1ab(i,ii,iv)+2ab(i,ii,iv), ver 3.1; date assessed: August 13, 2015

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Common name(s): English: Muhlenberg’s Smile

Identification Information: The species can be recognized by its occurrence on non-calcareous rocks and bright yellow thallus withrounded dark purple-black disc-like fruiting bodes.

ASSESSMENT JUSTIFICATION [criteria: A2c; B1ab(i,ii,iv)+2ab(i,ii,iv)]

Rinodina chrysomelaena is a bright yellow crustose lichen occurring on non-calcareous rocks atscattered locations in the Appalachian Mountains of eastern North America and Mexican Highlands of Oaxaca, Mexico. The species can be recognised by its occurrence on non-calcareous rocks and bright yellow thallus with rounded dark purple-black disc-like fruiting bodies. This is an easily recognised lichenendemic to North America (including Mexico) that is considered to be extirpated from more than 95% of its historical range. Extensive efforts to relocate historical populations have failed and only two extant populations are known, both occurring in a highly limited geographic area. This species has been assessed as Critically Endangered, based on the pre-1990 vs. post-1990 reduction of extent ofoccurrence (EOO) to <100 km², this reduction has resulted in a population decline of 77% over the past three generations, and the total range of species has reduced by 95%. Area of occupancy (AOO) (8 km²post-1990), and the extirpation of all known historical populations (balanced by discovery of two extant populations). In both cases the ranking is supported by 1) the extensive fragmentation of natural habitats and populations (both historical and modern), 2) severely fragmented, small number of extant populations (2), 3) decline in EOO, AOO, and total number of populations inferred from documented occurrences, and 4) historical and ongoing habitat degradation. The species also meets the criteria for Critically Endangered C2a(i,ii) based on the small number of mature individuals, the continuing decline in the number of locations, and the small number of mature individuals in the sole remaining subpopulation together with the fact that 100% of the remaining individuals exist within one subpopulation. The categorisation as Critically Endangered is based on the documented losses in number of populationsas well as reductions of EOO and AOO. The causes of this reduction are unknown, but inferred to be the large scale degradation and loss of habitats throughout the range of the species. These losses have occurred in the past, are ongoing at present at smaller scales, and will likely continue in the future.

Assessor/s: Lendemer, J., Allen, J., McMullin, T. & Tripp, E.; Reviewer/s: Scheidegger, C.

Bibliography:

Degelius, G N. (1941) Contributions to the Lichen flora of North America II. The lichen flora of the Great Smoky Mountains. Arkiv för Botanik 30A: 1-80.

Drummond, M.A. & Loveland T.R. (2010) Land-use pressure and a transition to forest-cover loss in theeastern United States. Bioscience 60(4): 286-298.

IUCN (2018) The IUCN Red List of Threatened Species. Version 2018-2. Available at: www.iucnredlist.org. (Accessed: 15 November 2018).

Lendemer, J. C. & Sheard, J.W. (2006) The typification and distribution of Rinodina chrysomelaena (Physciaceae), a rare eastern North American lichen. The Bryologist 109(4): 562-565.

Lendemer, J.C., E. Tripp & J.W. Sheard (2014) A review of Rinodina (Physciaceae) in Great Smoky Mountains National Park highlights the growing significance of this “island of biodiversity” in eastern North America. The Bryologist 117(3): 259-281.

Lendemer, J.C., R.C. Harris & E.A. Tripp (2013) The lichens and allied fungi of Great Smoky Mountains National Park: an annotated checklist with comprehensive keys. The New York Botanical Garden Press, Bronx, New York.

Napton, D.E., Auch, R.F., Headley, R. & Taylor, J.L. (2101) Land changes and their driving forces in theSoutheastern United States. Regional Environmental Change 10(1): 37-53.

Sheard, J.W. (2010) The Lichen Genus Rinodina (Lecanoromycetidae, Physciaceae) in North America, North of Mexico. National Research Council of Canada, NRC Research Press, Ottawa.

Find out more about the IUCN Red List Categories and Criteria here.

Page 562.

Type. U.S.A. PENNSYLVANIA. (Lancaster or Berks Co.), 25 Feb. 1801, G.H.E. Muhlenberg 106c (PH - lectotype!, Lendemer & Sheard, 2006). Lecanora chrysomelaina [sic] Muhl., nomen nudum, Cat. Pl. Amer. Sept.: 101 (1813); Parmelia chrysomelaena (Ach.) Spreng., Car. Linn. Syst. Veg. 4: 296 (1827). Dimelaena chrysomelaena (Ach.) Hale & W. Culb. Bryologist 73: 513 (1970).

Description. Thallus thick, citrine, composed of discrete areoles at first, becoming contiguous; areoles to 0.60‑1.80 mm wide, sublobate, lobes to ca. 0.30 mm wide and sometimes overgrowing each other; surface plane, matt; margin indeterminate; prothallus sometimes visible at base of areoles, black; vegetative propagules absent.  Apothecia broadly attached to narrowly attached, frequent, contiguous or not, to 0.50-1.20 mm in diam.; disc persistently plane, reddish‑brown to black; thalline margin concolourous with thallus, 0.10‑0.15 mm wide, entire or flexuose, persistent; excipular ring absent. Apothecial Anatomy. Thalline exciple 70‑120 µm wide laterally; cortex 10‑30 µm wide; epinecral layer absent; cortical structure occluded by crystals; medulla also with crystals; algal cells to 8.0‑17.0 µm long; thalline exciple 80‑135 µm wide below; cortex 35‑50 µm wide; proper exciple hyaline, 5‑15 µm wide laterally, sometimes expanded to 20 µm above; hypothecium hyaline, 60‑140 µm deep, extending as a stipe to prothallus; hymenium 85‑125 µm high, not inspersed; paraphyses 1.5‑2.5 µm wide, not conglutinate, apices to 3.0‑4.5 µm wide, lightly pigmented and immersed in dispersed pigment forming a red‑brown epihymenium; asci 70‑85 x 17‑28 µm. Ascospores 8/ascus, developmental type A, Physcia‑type, (19.5-)24.0‑26.0 (-30.5) x (10.0-)11.0‑12.0(-13.5) µm, average l/b ratio 2.0-2.3, larger spores markedly curved, retaining thick apical walls; torus well developed; walls not ornamented. Pycnidia not observed.

Chemistry. Spot tests, K‑, C‑ or C+ faint orange, P‑; secondary metabolites, atranorin (major), chloroatranorin (trace), secalonic acid W (major), secalonic acid A (minor or trace), eumitrin Y (submajor), unknown secalonic acid derivatives (trace) (Elix, personal communication).

Substrate and Ecology. Saxicolous, sometimes over mosses and associated with blue‑green algae. Poelt and Mayrhofer (1988) have shown that R. chrysomelaena probably has an obligate relationship with Stigonema species, forming external pseudocephalodia. A similar, but less permanent relationship was also shown for R. badiella (= R. tephraspis). The authors note that both species have lobate thalli. This may be due to the relatively rapid growth rate that the cyanobacterium associations allow.

Distribution. Rinodina chrysomelaena is a rare North American endemic, ranging from the northeastern seaboard region to the southern Appalachians and recently extended to Oaxaca State, Mexico (Lendemer & Sheard 2006). The phytogeographical connection between the Southern Appalachians and the Mexican Highlands has previously been noted by Yoshimura and Sharp (1968) and Dey (1976, 1979). The distribution of R. chrysomelaena is unusual within such species in that it extends so far north.

In addition to the localities mapped by these authors there are collections by Ravenel from Georgia (BM, FH), lacking locality details but presumably from the extreme north of the state. Records from Hawaii (FH) and Florida (US) may have been mislabeled by Eckfeldt and are not included in the locality listing or distribution map.

The paucity of records of this rather striking lichen suggests that R. chrysomelaena has always been a rare species. It was last recorded by Degelius (1941) from Cherokee Orchard, Great Smoky Mountains National Park where he noted that it was rather abundant. Tønsberg (personal communication) recently searched this locality without finding the species and noted that the site is now occupied by closed, second growth, a habitat probably not suited to this species. It is feared that the species my no longer be extant in the United States, likely having succumbed to air pollution on the exposed ridges that it mostly occupied.

Notes. The citrine pigmentation of the cortex and medulla of this species make it impossible to confuse with any other North American saxicolous Rinodina although specimens of Dimelaena oreina (Ach.) Norm. and Buellia ocellata (Flotow) Körb. (Sheard 1969), both “yellow” species, have been mistaken for it. Its lobate areoles were the reason that Hale and Culberson (1970) included the species in Dimelaena. However, the Physcia‑type spores indicate that the true relationship lies with the genus Rinodina. Immature spores are unusual in that their walls appear to be two layered, which may reflect a particularly wide perispore. The thallus morphology is reminiscent of some forms of R. tephraspis. This species has a grey to brown thallus with smaller spores belonging to the Teichophila-type. In some collections R. chrysomelaena is found growing over mosses on the saxicolous substrate which may confirm that it is a relatively fast growing species.

Lendemer and Sheard (2006) noted that the species has been incorrectly cited as Rinodina chrysomelaena Tuck. in North American checklists (Esslinger and Egan 1995) perpetuating an error made by Zahlbruckner (1931). Those interested in the nomenclatural details should refer to refer to the first mentioned paper.

Specimens examined. U.S.A. GEORGIA. H.W. Ravenel (BM, F). MASSACHUSETTS. Bristol Co., New Bedford (FH); H. Willey (UPS); 1868, H. Willey (US); H. Willey  451 (FH); Essex Co., Lynn, 1844, E. Tuckerman (FH). NORTH CAROLINA. Gaston Co., Crowders Mountain, 1883, J.W. Eckfeldt [H.A. Green] (PH). PENNSYLVANIA. Chester Co., H.B. Michener (FH). SOUTH CAROLINA. Chester Co., Chester, J.W. Eckfeldt (US). TENNESSEE. 1890, W.W. Calkins (H-Nyl); Hamilton Co., Lookout Mountain (WIS); W.W. Calkins (FH, MICH, MIN); 1890, W.W. Calkins (NY); 1892, W.W. Calkins (UC); Sevier Co., Cherokee Orchard, 1939, G. Degelius (FH, UPS, US).

Reference. Lendemer & Sheard (2006 Figures 1, 2).