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Ramalina americana

Ramalina americana
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Fungi
Division: Ascomycota
Class: Lecanoromycetes
Order: Lecanorales
Family: Ramalinaceae
Genus: Ramalina
Species:
R. americana
Binomial name
Ramalina americana
Hale (1979)

Ramalina americana, commonly known as the sinewed ramalina, is a pale green fruticose lichen that is found across the Northern US Midwest, extending into Southern Canada and the Eastern Seaboard. It is characterized morphologically by the presence of pseudocyphellae, straight spores, and its unique chemical diversity.[1]

Taxonomy

The species first characterized by American lichenologist Mason Hale in 1978, who distinguished it from the similar European species Ramalina fastigiata. The type specimen was collected by Clara Eaton Cummings in Plymouth, New Hampshire, and featured in her work Decades of North American Lichens no. 43.[2] A vernacular name used for the species is "sinewed ramalina".[3]

Morphology

Note the apothecia growing from the tips of the thallus as well as the narrow, divided branches.

R. americana grows as a pale green thallus from a singular holdfast.[1] It features narrow, divided branches that are marked with depressions and ridges. The apothecia grow close or on the tips of the branches. Its spores are predominantly straight, and it has pseudocyphellae on the thallus surface.[4] It contains the lichen product usnic acid.[2]

Distribution

R. americana is found throughout the Midwest, southern Canada, and areas of the Eastern coastline. The Ramalina genus is well distributed and highly prolific. R. americana is obligately epiphytic, growing exclusively attached to the bark of living trees, as opposed to Ramalina siliquosa, which grows on rocks.

Taxonomy and chemotyping

Ramalina americana features a well studied chemotype that has frequently undergone varying taxonomic reclassification. When first differentiated by Hale in 1978, it was described both as having a largely acid-deficient population in the northern ends of its range, as well as a much more chemically diverse southern distribution featuring five varying chemotypes.[2][5] These chemotypes were later classified by Jonathan Dey in 1978, who discovered a varying range of depsidones, acids, and other lichen products.[6]

In 1999, genetic internal transcribed spacer regions were used to identify a considerably similar sequence data compared to the highly varying chemotypes of neighboring R. americana populations. These results suggested similar biosynthetic pathways for many of the secondary metabolites produced in the R. americana chemotype.

The same 1999 study identified an unlikelihood that environmental variation results in the variation in the chemotypes as observed.[5] Other studies attribute some variation in chemotype to potential gene-environment interactions, but still emphasize the consistent genetic inheritance of chemotypical variance.[7]

Findings in the 1999 study identify a potential polyphyly of the southeastern chemotype rich R. americana varieties, and further separated the northern, acid deficient species as R. americana, and the southern distribution as R. culbersoniorum. This was further expanded upon in a study in 2012 that revealed despite evidence for monophyly[8] found in 2004, novel ITS data further emphasized a low support for monophyly.[9] In 2020, the separation of the R. americana chemotype complex into two distinct species was reemphasized in a new paper.[10]

Evolutionary history

Ramalina americana is presumed to have differentiated from its European sister species, Ramalina fastigiata.[5]

References

  1. ^ a b Culberson, Chicita F.; Culberson, William Louis; Johnson, Anita (1990). "The Ramalina americana complex (Ascomycotina, Ramalinaceae): chemical and geographic correlations". The Bryologist. 93 (2): 167–186. doi:10.2307/3243621. JSTOR 3243621.
  2. ^ a b c Hale, Mason E. (1978). "A new species of Ramalina from North America (Lichenes: Ramalinaceae)". The Bryologist. 81 (4): 599–602. doi:10.2307/3242352. JSTOR 3242352.
  3. ^ Brodo, Irwin M.; Sharnoff, Sylvia Duran; Sharnoff, Stephen (2001). Lichens of North America. Yale University Press. pp. 621–622. ISBN 978-0300082494.
  4. ^ Brodo, Irwin M. (2001). Lichens of North America. Sylvia Duran Sharnoff, Stephen Sharnoff, Canadian Museum of Nature. New Haven: Yale University Press. ISBN 0-300-08249-5. OCLC 45100151.
  5. ^ a b c LaGreca, Scott (1999). "A phylogenetic evaluation of the Ramalina americana chemotype complex (lichenized Ascomycota, Ramalinaceae) based on rDNA ITS sequence data". The Bryologist. 102 (4): 602–618. doi:10.2307/3244250. JSTOR 3244250.
  6. ^ Dey, Jonathan P. (1978). "Fruticose and foliose lichens of the high-mountain areas of the southern Appalachians". The Bryologist. 81 (1): 1–93. doi:10.2307/3242271. JSTOR 3242271.
  7. ^ Stocker-Wörgötter, Elfriede (2001). "Experimental lichenology and microbiology of lichens: culture experiments, secondary chemistry of cultured mycobionts, resynthesis, and thallus morphogenesis". The Bryologist. 104 (4): 576–581. doi:10.1639/0007-2745(2001)104[0576:ELAMOL]2.0.CO;2. JSTOR 3244591.
  8. ^ Stocker-Wörgötter, Elfie; Elix, John A.; Grube, Martin (2004). "Secondary chemistry of lichen-forming fungi: chemosyndromic variation and DNA-analyses of cultures and chemotypes in the Ramalina farinacea complex". The Bryologist. 107 (2): 152–162. doi:10.1639/0007-2745(2004)107[0152:scolfc]2.0.co;2.
  9. ^ Timsina, Brinda A.; Stocker-Wörgötter, E.; Piercey-Normore, Michele D. (2012). "Monophyly of some North American species of Ramalina and inferred polyketide synthase gene function". Botany. 90 (12): 1295–1307. doi:10.1139/b2012-097.
  10. ^ LaGreca, Scott; Lumbsch, H. Thorsten; Kukwa, Martin; Wei, Xinli; Han, Jeong Eun; Moon, Kwang Hee; Kashiwadani, Hiroyuki; Aptroot, André; Leavitt, Steven D. (2020). "A molecular phylogenetic evaluation of the Ramalina siliquosa complex, with notes on species circumscription and relationships within Ramalina". The Lichenologist. 52 (3): 197–211. doi:10.1017/S0024282920000110. S2CID 225913111.
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