Niebla eburnea
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Fungi
Division: Ascomycota
Class: Lecanoromycetes
Order: Lecanorales
Family: Ramalinaceae
Genus: Niebla
Species:
N. eburnea
Binomial name
Niebla eburnea
Spjut (1996)

Niebla eburnea is a fruticose lichen that grows on rocks along the foggy Pacific Coast of North America, from Mendocino County in California south to near Punta Santa Rosalillita in Baja California, and also in the Channel Islands.[1][2] The epithet, eburnea is in reference to the ivory like appearance of the cortex.[1]

Distinguishing features

Niebla eburnea is best recognized by the ivory-like cortex, appearing mostly smooth except for the creamy pastry-like ripples or creases, occasionally with transverse cracks; the thallus divided into subterete branches, generally half-twisted near base and often near apex, otherwise branches straight to curved, often with short elliptiform dilated segments, near apex more like the palm of the hand from which various claw-like to finger-like branchlets spread, often blackened around the base to a short distance above. Black dot-like pycnidia common along the margins, their development associated with thickened crinkled margins on the upper parts of branches and lobes. Niebla eburnea is further characterized by the presence of the lichen substance divaricatic acid, along with triterpenes and pigments concentrated near base.[1]

The ivory-like cortex of Niebla eburnea is 65–125 µm thick, in contrast to that of Niebla cornea, 45–60 µm thick, a similar species that also differs in having the lichen substance sekikaic acid.[1] Although Niebla eburnea can often be distinguished by its morphology, thin-layer-chromatography is a more definitive way to identify the species—by its lichen substance of divaricatic acid, with accessory triterpenes—in contrast also to Niebla disrupta, which has sekikaic acid and to species in the genus Vermilacinia that lack the depsides and have distinctive terpenes not found in Niebla; Vermilacinia laevigata and Vermilacinia procera are examples of species that can be confused with N. eburnea.[1][2]

Taxonomic history

Niebla eburnea was recognized as distinct from Niebla homalea before it was described. On 30 April 1985 while collecting a minimum 25 gram samples near Cerro Solo in northern Baja California for a biodiversity screening of lichens in the search of new drugs by the National Cancer Institute (NCI) Natural Products Branch to treat HIV, it was considered to represent another species that differed from Niebla homalea that had been collected near Punta Banda on the day before (29 April 1985, WBA-277, S & M 9032C, 58 g).[3] The sample for Spjut & Marin 9047A was not submitted to the NCI. Instead approximately 40 specimens from the sample were extracted with acetone to identify the lichen substances by thin-layer chromatography. All contained divaricatic acid, with accessory triterpenes. This material then became the type collection for Niebla eburnea, described by Richard Spjut in 1996,[1] and for exsiccati distributed later to other institutions through the ABLS Lichen Exchange[4] that was at Arizona State University.

It may be noted that Niebla eburnea has been treated as belonging to a broad spectrum of morphological and chemical variation in Niebla homalea that includes many different species of Niebla and Vermilacinia. This does not mean that Niebla eburnea is an equal synonym (taxonomy) as erroneously indicated by some.[2] This synonymy is based on the subjective interpretation of one taxonomic review of the genus[5] which has many errors and inconsistencies.[6]

References

  1. 1 2 3 4 5 6 Spjut, R. W. 1996. Niebla and Vermilacinia (Ramalinaceae) from California and Baja California. Sida Bot. Misc. 14
  2. 1 2 3 Niebla eburnea reported in Spjut (1996) as far north as Sonoma County; Mendocino County report from images shown and described on Enlichment web page titled Niebla homalea (Ach.) Rundel & Bowler, not all Niebla homalea according to Spjut (1996); Niebla eburnea, 1st and 12th images by Curtis Björk (Jughandle State Preserve, Mendocino County, 2011-07-09), 10th image by Jason Hollinger (Navarro State Park, 2007-02-24), a total of 14 images exhibited, 6 species represented. Other images in sequence are of Niebla disrupta (2nd & 12th images, Curtis Björk, Jughandle Preserve, 2011-07-09), N. homalea (3rd Jason Hollinger & 8th Curtis Björk images, Salt Point State Park, Jughandle State Park, 2007-02-24; 2011-07-09), Vermilacinia procera with Niebla testudinaria (4th image, Pt. Lobos St. Park), Vermilacinia combeoides (5th image), and Niebla cornea (6th, 7th & 9th images)
  3. ↑ Samples of lichens were collected from the Eastern and Western regions of the United States and Baja California, Mexico for anti-HIV screening during 1985. Prior to 1982, samples for antitumor screening were supplied in 1 kilogram (kg) quantity (dried) to the NCI by the USDA Agricultural Research Service. In October 1982, the funding for this cooperative agreement was terminated. World Botanical Associates (WBA) was formed by Richard Spjut in May 1983 to continue to supply samples for antitumor screening. Lichens were considered a potential novel source for new anti-HIV drugs since they had rarely been collected for the NCI antitumor screening program. Richard Spjut, the Senior Partner of WBA, proposed that the NCI reduce their 1 kg quantity to 25 grams in order to obtain a broad diversity of lichen samples. The NCI group maintains an inventory of natural product extracts with details on the collection data. Voucher specimens are deposited at the United States National Herbarium (Smithsonian Institution) and cited in Spjut's 1996 revision of the genus under N. homalea.
  4. ↑ ABLS Lichen Exchange, retrieved 21 Dec 2014
  5. ↑ Bowler, P. and J. Marsh. 2004. Niebla. ‘Lichen Flora of the Greater Sonoran Desert 2’: 368–380.
  6. ↑ Lichen Flora of the Greater Sonoran Desert: Book Review, Richard Spjut, web page retrieved 21 Dec 2014, http://www.worldbotanical.com/lichen%20flora%20review.htm
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