Physcia
Physcia (Schreb.) Michx., 1803
| Common name | Rosette Lichens | |
|---|---|---|
| Field Characters | Small, foliose, chlorolichens. Thalli blue-grey, green-grey to white, composed of lobes appressed to ascending, mainly <2 mm wide. Upper cortex may be pruinose or maculate, typically matte, lacking longitudinal striae. Vegetative propagules often present, either isidia or soredia, or absent and then commonly fertile. Cilia present in a few species, otherwise absent. Lower cortex present, white to pale brown, with hyphae oriented longitudinally (prosoplectenchymatous). Rhizines simple or sparsely branched, white to pale brown with dark tips, typically concolorous with the lower cortex. Apothecia with black, often pruinose disc, thalline margin concolorous with the upper cortex, either adnate to the thallus or short-stipitate. | |
| Similar species & genera |
Anaptychia & Heterodermia: species in Alberta lack a lower cortex, and have a finely striate upper cortex (prosoplectenchymatous).
Imshaugia: upper cortex and medulla K+ deep yellow, PD+ orange (thamnolic acid), more crepey in texture than matte. Parmeliopsis hyperopta: lower cortex brown, all similar species of Physcia have a pale lower cortex (Brodo et al. 2001). Phaeophyscia: upper cortex K-, typically darker, lower cortex typically black, rhizines typically black with white tips. Phaeophyscia constipata is tricky as it can resemble a Physcia, but it has a K- cortex (no substances detected). Physciella: upper cortex K-, reported but not confirmed for Alberta. The reality is you need a careful examination of the upper and lower cortices and likely some chemistry when learning to discriminate these genera. |
|
| Ecology | Varies from saxicolous to epiphytic and on downed wood, with some species wide-spread and abundant in multiple regions, others rare and restricted in range. | |
| Chemistry | Cortex K+ yellow, KC-, C-, PD- or PD+ pale yellow, UV- (atranorin). Medulla K- or K+ yellow, KC-, C-, PD- or PD+ pale yellow, UV- (±atranorin [an important trait distinguishing some species], ±zeorin or other triterpenes detected via thin layer chromatography). | |
| Molecular support |
In progress. | |
| Links |
Species recorded in Alberta: 11? Expect future shakeups in nomenclature. Physcia tenella also recorded in Alberta but based on herbarium redeterminations, collections are misidentified Physcia adscendens or Hetermodermia spp.; similarly, Physcia millegrana is recorded for AB but may be misidentifications of Physcia affinity dimidiata so the latter 2 species were not included in this key (Haughland et al. 2022). We may have actual Physcia dimidiata, but the material in the interior and urban regions is not P. dimidiata s.s., and will be referred to as P. affinity dimidiata until it is formally described. It is almost certain that P. stellaris s.s. does not occur in Alberta, and that our specimens represent another undescribed species.
- P. adscendens (Fr.) H. Olivier ACIMS
- P. aipolia (Ehrh. ex Humb.) Fürnr. var. aipolia ACIMS
- P. alnophila (Vainio) Loht., Moberg, Myllys & Tehler (Lohtander et al. 2009) ACIMS
- P. biziana (A. Massal.) Zahlbr. ACIMS
- P. caesia (Hoffm.) Fürnr. ACIMS
- P. dimidiata (Arnold) Nyl. ACIMS
- P. affinity dimidiata, sp. nov. The majority of Alberta material is not P. dimidiata s.s. and represents an undescribed species
- P. dubia (Hoffm.) Lettau ACIMS
- P. phaea (Tuck.) J. W. Thomson Syn.: Parmelia phaea ACIMS
- P. affinity stellaris, sp. nov. Alberta material is not P. stellaris s.s. and represents an undescribed species
- P. subtilis Degel. AB! (NA) In Can. Museum of Nature, collected by P.Y. Wong
Click for a doc key to Alberta’s Physcia_v2025
RENR Students: Know Physcia adscendens, P. aipolia/alnophila (as a group)– be able to key these species out or recognize them. Most species are also covered in Brodo et al. 2001 and Goward et al. 1994, with the following exceptions: Brodo does include P. alnophila or P. dimidiata, Goward has P. alnophila as a variety of P. aipolia, and Goward does not include P. subtilis.
Resources
Brodo, I. M. 2016. Keys to the lichens of North America. Revised and Expanded. Yale University Press, in collaboration with the Canadian Museum of Nature.
Brodo, I. M., C. Freebury & N. Alfonso. 2013. Notes on the lichens Physcia aipolia and P. alnophila in North America. Evansia 30: 110–119.
Brodo, I. M., S. D. Sharnoff, and S. Sharnoff. 2001. Lichens of North America. Yale University Press, New Haven and London.
Esslinger, T. L. 2016b. Key to Physcia species in North America. March 2016, unpublished.
Esslinger, T. L., S. D. Leavitt & B. McCune. 2020. Two closely related but morphologically disparate new species of Physcia from western North America. The Bryologist 123: 204–214.
Goward, T., B. McCune, and D. Meidinger. 1994. The Lichens of British Columbia Illustrated Keys. Part 1 – Foliose and Squamulose Species. Ministry of Forests Research Program, Province of British Columbia.
Haughland, D. L., A. Hood, D. Thauvette, S. A. Toni, M. Cao, J. D. Birch, J. Wasyliw, L. Hjartarson, M. Villeneuve, A. Stordock, D. A. Fielder, M. Lewis, D. Evans, D. Royko, R. Bolduc, H. Webster, J. D. Singh, K. A. Schafer, S. Goyette, H. E. Davidson & C. Shier. 2022. Getting to know our neighbours: 108 urban lichens of Edmonton, Alberta, Canada, and an initial assessment of their utility as community-science indicators. Opuscula Philolichenum 21: 33-181. https://www.nhm2.uio.no/botanisk/lav/RLL/PDF/R43924.pdf
Helms, G., T. Friedl & G. Rambold. 2003. Phylogenetic relationships of the Physciaceae inferred from rDNA sequence data and selected phenotypic characters. Mycologia 95: 1078–1099.
Lohtander, K., M. Kӓllersjö, R. Moberg & A. Tehler. 2000. The family Physciaceae in Fennoscandia: phylogeny inferred from ITS sequences. Mycologia 92: 728–735.
Moberg, R. 2002. Physcia. – In T.H. Nash III, B.D. Ryan, C. Gries and F. Bungartz (eds), Lichen Flora of the Greater Sonoran Desert Region Volume 1: 358–373.
Thomson, J. W. 1963. The Lichen Genus Physcia in North America. Nova Hedwigia 7.
