• Proposed
  • 2Under Assessment
  • 3Preliminary Assessed
  • 4Assessed
  • 5Published

Phlyctis petraea R.C. Harris, Muscavitch, Ladd & Lendemer

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Scientific name
Phlyctis petraea
R.C. Harris, Muscavitch, Ladd & Lendemer
Common names
Eggshell Rock Blaze
IUCN Specialist Group
Assessment status
Proposed by
James Lendemer
Comments etc.
James Lendemer

Assessment Notes

Taxonomic notes

As is discussed in detail by Muscavitch et al. (2017) this species has been collected for nearly a century, and recognized as distinct for more than fifty years. However it was only formally described in 2017.

Why suggested for a Global Red List Assessment?

Geographic range

Phlyctis petraea is endemic to North America where it is widespread in the eastern United States and parts of adjacent Canada (Muscavitch et al. 2017).

Population and Trends

Complete, detailed population data are unavailable for this taxon. However, it is suspected to be stable as it is common and widespread in many different habitats (Muscavitch et al. 2017).

ASSESSMENT: Least Concern
Given the large number sites where it is extant, large geographic range, large population size, and absence of documented or suspected declines, the species does not meet the thresholds for any threat criteria.

Population Trend: Stable

Habitat and Ecology

Although Phlyctis petraea has a wide geographic distribution in temperate eastern North America, it grows almost exclusively on sheltered and protected rock overhangs. Nearly all known occurrences are from non-calcareous rocks, especially sandstones, however it has occasionally been found on calcareous rocks such as limestone. A small number of records are from the bases of hardwood trees.

Temperate Forest


The primarily threat to this species is urbanization as it does not typically occur in urban areas. Otherwise it occurs at sites that span a wide range of habitat qualities.

Housing & urban areasCommercial & industrial areas

Conservation Actions

Many sites where this species occurs are located on public lands and in protected areas where it is incidentally protected. This species would benefit from broader awareness and training as to the impacts of urbanization generally on lichens.

Formal educationTrainingAwareness & communications

Research needed

This species would benefit from demographic studies and long-term monitoring of both habitat and population trends.

Population size, distribution & trendsPopulation trendsHabitat trends

Use and Trade

Phlyctis petraea has been used to study the impacts of climbing on crustose rock-dwelling lichens (Clark & Hessl 2005) and to study remote detection of lichen communities (Wasklewicz et al. 2007).


Country occurrence

Regional Population and Trends

Country Trend Redlisted