Observation 33642: Physcia stellaris (L.) Nyl.
When: 2010-02-07
Herbarium specimen reported

Notes: Locality: 35°12’47.92"N, 85°55’20.20"W, el. 586 m. Woodlands.

Substrate and habitat: Growing on a branch of scarlet oak, Quercus coccinea, brought to the ground by recent rain storms, in a park-like residential area bordering oak-dominated eastern deciduous woodland at the western rim of the Cumberland Plateau.

Chemistry:
cortex: C-, K-, KC- [K+ yellow expected]
medulla: C-, K-, KC- [K- perhaps not reliable because the thallus is so small]

Identification: These cute little corticolous Physcia are common at Sewanee, but identification can be a challenge. Here is a summary of the characteristics of three candidates drawn from the discussions in Brodo, et al. (2001) and Harris and Ladd (2005):
Physcia aipolia (medulla K-; thallus conspicuously spotted; lobes flat to concave or upturned at the tips, 1-2(-3)mm wide)
Physcia pumilior (medulla K+ yellow “but usually too scanty to test” (Brodo); “conspicuous white spots on all parts of the thallus” (Brodo); lobes generally convex, 0.3-0.5mm wide)
Physcia stellaris (medulla K-; thallus “smooth and uniform although sometimes with some white spotting” (Brodo) or “typically with prominent spots” (Harris and Ladd); lobes flat to convex, 0.5-1.5(-3)mm wide; TLC can distinguish P. stellaris from the other two species)
The lichen of the present observation is quite small. The longest diameter of its thallus is only about 8mm, so its tiny convex lobes clearly fall within the smallest size range. On that basis, it is tentatively assigned to Physcia pumilior.

References:
Sharnoff’s Physcia pumilior gallery
CNALH images and locality map, and a larger, interactive locality map.

Voucher specimens:
United States, Tennessee, Franklin County, Sewanee, Woodlands. 07 Feb 2010. Chris Parrish 0048, det. James C. Lendemer (NY)

Common name: star rosette lichen

Species Lists

Images

78223
thallus and apothecia, 16x
78221
78222
thallus and apothecia, 10x
78224
thallus and apothecia, 20x
78225
lobes and upper cortex, 40x

Proposed Names

28% (1)
Eye3
Used references: Brodo, Sharnoff, and Sharnoff, 2001, pp.546-560; Harris and Ladd, 2005, pp.190-193
92% (2)
Eye3 Eyes3
Used references: Specimen identified by James C. Lendemer (NY)

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Eye3 = Observer’s choice
Eyes3 = Current consensus

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Created: 2010-02-15 21:36:48 EST (-0500)
Last modified: 2010-05-02 08:50:26 EDT (-0400)
Viewed: 343 times, last viewed: 2016-09-25 15:30:00 EDT (-0400)
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