Cryptic paw (Nephroma occultum) COSEWIC assessment and status report: chapter 3

Species Information

Name and classification

Scientific name:

Nephroma occultum Wetm.

Synonyms:

None

Common names:

Cryptic paw lichen, Cryptic kidney lichen

Family name:

Nephromataceae

Major group:

Lichens (lichenized Ascomycetes)

Bibliographic citation:

Bryologist 83: 243-247 (1980)

Type specimen:

Oregon, Lane County, 11.2 km NE of Blue River, H.J. Andrews Experimental Forest, February 19, 1978, Scott Sundberg 120.

  • Holotype: University of Minnesota (MIN).
  • Isotypes: National Museum of Natural Sciences, Ottawa (CANL).
    Oregon States University, Corvallis (OSC).
    Swedish Museum of Natural History, Stockholm (S).
    Smithsonian Institution, Washington, D.C. (US).

Morphological description

Nephroma occultumis a rounded, loosely appressed, foliose (leaf) lichen 2-7 cm broad with lobes 4-12 mm wide (Brodo et al. 2001). The upper surface is dull, naked, pale yellowish grey to greenish or bluish grey, and is distinctly net-ridged throughout. The lower surface is also dull and naked, but is finely wrinkled, and varies in colour from pale tan at the margins to sometimes blackish toward the centre. The lobe margins are even and distinctly rounded in outline. Coarse, granular soredia, 80-330 µm diameter, are present along the lobe margins, and later develop also on the ridges of the upper surface. The medulla is white and is UV + pale yellow, and the cortex is KC yellow. The photobiont is a cyanobacterium (Nostoc). Apothecia and pycnidia are unknown.

According to White and James (1988), Nephroma occultumproduces the secondary chemical products nephroarctin, phenarctin, usnic acid, zeorin and an unidentified triterpenoid. These results are based on material from the holotype locality, in west central Oregon. Six further specimens from different parts of British Columbia have now been tested with two-dimensional chromatography, and have yielded two additional accessory unidentified triterpenoids (Goward 1995a).

Technical descriptions are found in Wetmore (1980) and White and James (1988).

Field characteristics that help identify Nephroma occultum include the foliose habit, net-ridged upper surface, sorediate ridges, pale yellowish grey to bluish grey colour, and naked lower surface. Some forms of N. parile (Ach.) Ach. are similar, but in that species the upper surface is usually brownish and is at most weakly wrinkled, never net-ridged (Goward 1995a).

The name Nephroma occultum is derived from the Latin “occultus”, which means hidden (Wetmore 1980); the earliest collections of this species were found hidden in the uppermost branches of large old trees in Oregon.

Illustrations of Nephroma occultum are found in Wetmore (1980: holotype), White and James (1988: isotype), McCune and Geiser (1997), Brodo et al. (2001), and Figures 1, figure2 and figure3 of this report.

Figure 1. Nephroma occultum (photo: Stephen Sharnoff)

Figure 1.Nephroma occultum

Figure 2. Nephroma occultum (photos: Bruce McCune)

Figure 2. Nephroma occultum

Figure 3. Nephroma occultum (photo: Patrick Williston)

Figure 3.   Nephroma occultum

Genetic description

Nephroma occultum has not been the subject of genetic investigation to date; however, other species in the genus have been studied in recent cladistic analyses using ITS sequencing (Stenroos et al. 2003, Maidlikowska and Lutzoni 2004). These studies have shown the genus Nephroma to be a monophyletic group, implying that the genus should remain taxonomically stable.

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