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Hypotrachyna riparia McCune

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Scientific name
Hypotrachyna riparia
Common names
IUCN Specialist Group
Assessment status
Assessment date
IUCN Red List Category
IUCN Red List Criteria
A4ce; B1ab(i,ii,iii,iv,v)+2ab(i,ii,iii,iv,v)
Stone, D., Villella, J. & Root, H.
Allen, J.

Assessment Notes

The content on this page is fetched from The IUCN Red List of Threatened Species: https://www.iucnredlist.org/species/195432681/195432683


Hypotrachyna riparia is known from nine locations in Oregon state in the United States of America. Large wildfires pose a serious threat to this species, and in 2020 one of the largest subpopulations was likely extirpated, and at minimum led to a 25% decline in the total population size. The invasion of the Emerald Ash Borer poses an additional threat to the species as it expands its range into Oregon in the coming years. Based on the species' ongoing decline, limited extent of occurrence and area of occupancy, and the ongoing decline of its habitat, it is assessed as Vulnerable (A4ce; B1ab(i,ii,iii,iv,v)+2ab(i,ii,iii,iv,v)).

Taxonomic notes

This species was originally described by McCune (1998) based on collections from two sites in Oregon.

Geographic range

This species is found in Oregon, United States of America. It is known from the foothills of the central western Cascade Range in Clackamas, Lane, Linn, and Marion Counties in Oregon. It has been documented in the Willamette National Forest in Oregon, the Northwest Oregon BLM District, and in Fisherman’s Bend Recreation Site and a nearby site in Linn County, Oregon.

Population and Trends

The site in Fisherman's Bend, Oregon (largest or second largest subpopulation) was impacted by a large wildfire in 2020. All individuals were lost in the fire, which represents ~25% reduction in the overall population size. A nearby site downriver from Fisherman’s Bend was not burned and has a small population. The trend in large-scale wildfires in the Pacific Northwest is projected to continue, which will likely lead to continued and future declines in the species' distribution as lichens are not resilient to fires (Miller et al. 2018). Furthermore, Hypotrachyna riparia primarily occurs on ash trees, and the invasive insect the Emerald Ash Borer is projected to move north into the lichen's range (Nisbet et al. 2015). Loss of the primary substrate for Hypotrachyna riparia is suspected to lead to substantial declines in the species' population size.

Population Trend: decreasing

Habitat and Ecology

Hypotrachyna riparia is most frequently found on shrubs, growing on twigs, and is also found on twigs and boles of deciduous trees such as Fraxinus latifolia.


This species is primarily threatened by large wildfires spreading through lowland forests on the west side of the Cascades. Controlled burns may pose a threat to undocumented locations. The Cottage Grove site is on BLM land and has a potential for logging impacts. The species occurred at Fisherman's Bend campground where intentional thinning to maintain the campground poses a threat. Following thinning, a wildfire destroyed most habitat and no Hypotrachyna riparia remain. The species is still extant in riparian forests nearby, along the North Santiam River, but it is close to spreading human populations where recreational use has an impact on the habitat. There is also a possible threat in an invasive species (the Emerald Ash Borer, Agrilus planipennis) which is anticipated to disperse to Oregon soon and would cause a loss of substrate and habitat (Nisbet et al. 2015). Ongoing logging activities in Pacific Northwest may pose an additional threat (Alig 2003).

Conservation Actions

It has been documented in the Willamette National Forest in Oregon, the Northwest Oregon BLM District, in Fisherman’s Bend Recreation Site on the North Santiam River and downstream on private land in Linn County, Oregon. It is currently listed as a rare species by the Oregon Natural Heritage Program. Monitoring extant subpopulations, surveys to locate undocumented occurrences, and research on fire and Emerald Ash Borer impacts would aid in conservation management for this species. This species should be protected at all sites where it occurs.

Use and Trade

This species is collected for scientific research purposes.

Source and Citation

Stone, D., Villella, J. & Root, H. 2022. Hypotrachyna riparia. The IUCN Red List of Threatened Species 2022: e.T195432681A195432683. https://dx.doi.org/10.2305/IUCN.UK.2022-1.RLTS.T195432681A195432683.en .Accessed on 4 August 2023

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