# bitter wart lichen

*Lepra amara*

Scratching this lichen's white spots releases a powerful bitter taste. Historically, this chemical defense (picrolichenic acid) was used as a substitute for quinine to treat malaria.

- **Taxonomy:** Fungi › Ascomycota › Lecanoromycetes › Pertusariales › Pertusariaceae › Lepra
- **IUCN Red List status:** Least Concern
- **Population trend:** stable
- **Biome:** forest
- **Habitat:** Bark of mature deciduous trees, especially oak and beech, in humid, semi-shaded woodlands.
- **Diet:** Photoautotrophic (produces energy via symbiotic green algae performing photosynthesis).
- **Range:** Europe, North America, Asia, North Africa
- **Size:** Crustose patches spanning 2 to 15 cm in diameter, often merging to cover larger bark areas.
- **Lifespan:** Decades to centuries, growing only a few millimeters each year.
- **Active:** diurnal
- **Threats:** Air pollution (especially sulfur dioxide), habitat loss from intensive forestry, and removal of old-growth host trees.
- **Safe to approach?:** Harmless to touch, but do not ingest. This lichen contains picrolichenic acid, making it intensely bitter. If you touch it, wash your hands before eating to avoid transferring the bitter taste to your mouth or eyes.

## Sources

- Plate: https://gaia-dex.com/species/391cccb4-5264-4190-837c-f3e1d4540a65
- iNaturalist: https://www.inaturalist.org/taxa/630835

- Conservation status: IUCN Red List category, as recorded by Gaia-Dex
- Photo: https://inaturalist-open-data.s3.amazonaws.com/photos/458914849/medium.jpeg (Michael J. Papay, CC-BY, via iNaturalist)

Habitat, diet, size and similar notes are AI-written summaries; check them against the linked sources before relying on them.