SPECIES FACT SHEETCommon Name: Riparian loop lichenScientific Name: Hypotrachyna riparia McCuneDivision: AscomycotaClass: LecanoromycetesOrder: LecanoralesFamily: Parmeliaceae

Technical Description: Thallus foliose, with distinct upper and lower surfaces (cortices), to 8 cm wide, irregularly branched, whitish gray to bluish gray, loosely attached to substrate. Lobes 1.5-5 mm wide, flat or undulate, margins often flexed downwards just behind the apices, with the apices erect and somewhat hooded, giving the tips an expanded, capitate appearance, the upper surface of which is covered with prominent patches of whitish to brownish, powdery soredia. Lower surface of thallus black, brown on the margins, densely covered with richly and repeatedly dichotomously-branched rhizines up to 0.5 mm long, often visible from above. Reproduction: Apothecia unknown. Soralia on upper surface, as described above. Photobiont a green alga.

Chemistry: upper surface of thallus K+ yellow, C-, KC-, P+ pale yellow, UV-; medulla K+ yellow to orange, C-, KC-, P+ orange or red, UV-.

Distinctive characters: 1) medium sized whitish gray to bluish gray, foliose thallus, 2) numerous, easily visible, dense, richly and repeatedly dichotomously branched black rhizines, 3) soralia near the lobe tips, 4) upper cortex is KC-, medulla is C-, KC-.

Similar species: Hypotrachyna revoluta also is greyish, but it has rhizines that are sparse and less elaborately branched, soralia scattered on the surface of the lobes but not at the tips, and the medulla is C+, KC+ red.

Hypotrachyna sinuosa also has soralia on the lobe tips but the thallus is yellowish-green or green, with usnic acid, the lobes are convex, the upper cortex is KC+ yellow and the medulla is K+ yellow to reddish.

Species of Parmotrema have long, mostly unbranched marginal cilia simple, unbranched rhizines, and much larger lobes (up to 12 mm wide).

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Species of Parmelia are about the same size and color. They have abundant rhizines, usually are more tightly attached to the substrate, and most species have a network of fine cracks on the upper cortex.

Other descriptions and illustrations: Exeter et al. (2016), McCune and Geiser (2009); McCune (1998); McCune (no date).

Life History: Details for Hypotrachyna riparia are not documented. Apothecia have not been found therefore dispersal is restricted to vegetative propagation via soredia, litterfall, and fragmentation.

Range, Distribution, and Abundance: Endemic to Oregon and Washington. Known from the foothills of the central western Cascade Range in Clackamas, Lane, Linn, and Marion Counties in Oregon.

National Forests and BLM Districts: Documented on the Willamette National Forest; suspected on the Mt. Hood National Forest and in the Columbia River Gorge National Scenic Area in Oregon. Documented on Northwest Oregon BLM District. Documented in Fisherman's Bend Recreation Site in Linn County, Oregon

Rare, probably undercollected.

Habitat: On deciduous shrubs and trees in riparian forests and wetlands below about 610 m in elevation, in foothills and river valleys. Known forest types are Fraxinus latifolia associations and mixed riparian forests containing Pseudotsuga menziesii, Tsuga heterophylla, Acer macrophyllum or Abies grandis.

Threats: Air pollution, narrowing of riparian buffers, and overcollecting may be the primary threats to Hypotrachyna riparia. Lichens of riparian forests in major drainages along the east side of the Willamette Valley are at risk from air pollution because of fog penetration and patterns of prevailing winds. The lichen flora at some sites in this area has been shown to be depleted (Klopatek et al. 2006; Geiser and Neitlich 2007). Changes in hydrology could damage riparian wetlands leading to removal of suitable substrates.

Conservation Considerations: Consider revisiting known localities and monitoring the status of populations. Lower-elevation streams are usually privately owned and protection cannot be assured except on federal lands. Search for new populations on federal and state lands. Riparian buffers, are not always sufficiently wide to protect these populations. Surveys in suitable habitat and protection of known sites should be a priority.

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Conservation rankings: Global: G1; National: NNR. Oregon: ORBIC List 3, S1, Sensitive; Washington not ranked.

Preparer: John A. Christy, with edits from Daphne Stone and Rob Huff, May 2008. Updated by Daphne Stone, March 2019.

References

Exeter, R., C. Glade and S. Loring. 2016. Rare Lichens of Oregon. Salem District BLM, Salem, OR 97306. 189 pp. https://archive.org/details/rarelichensofore00exet Accessed 19 January 2019.

Geiser, L.H. & P.N Neitlich. 2007. Air pollution and climate gradients in western Oregon and Washington indicated by epiphytic macrolichens. Environmental Pollution 145: 203-218.

Klopatek, J.M., M.J. Barry & D.W. Johnson. 2006. Potential canopy interception of nitrogen in the Pacific Northwest, USA. Forest Ecology and Management 234: 344-354.

McCune, B. (no date). Photograph of Hypotrachyna riparia. USDA Forest Service National Lichens and Air Quality Database and Clearinghouse. http://gis.nacse.org/lichenair/index.php?page=photos Last accessed 8 January 2019.

McCune, B. 1998. Hypotrachyna riparia, a new lichen from western North America. Bryologist 101: 448-450.

McCune, B. and L. Geiser. 2009. Macrolichens of the Pacific Northwest, Second Edition. Oregon State University Press, Corvallis, OR. 464 pp.

Oregon Natural Heritage Information Center. 2007. Rare, threatened

and endangered species of Oregon. Oregon Natural Heritage Information Center, Oregon State University. Portland. 100 pp.http://oregonstate.edu/ornhic/2007_t&e_book.pdf

PhotosAll photos by Scot Loring, personal collection.

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Thallus.

Thallus showing terminal soralia.

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Terminal soralium and branched rhizines.

Terminal soralia

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Branched rhizines.

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