Anisomeridium biforme

Anisomeridium biforme is a crustose lichen-forming fungus in the family Monoblastiaceae, distinguished by a thin, inconspicuous thallus that grows closely appressed to its substrate and small perithecial ascomata embedded within the surface. As with related species in this genus, it lacks a photobiont partner visible to the naked eye and instead forms an intimate symbiotic association typical of lichenized fungi, contributing to substrate weathering and providing microhabitat for invertebrates in the ecosystems it occupies. It does not move or behave in any active sense, instead persisting through slow radial growth and spore dispersal.

The species has been recorded across a broad geographic range spanning Europe, the Americas, Oceania, and parts of Asia, reflecting historical documentation on calcareous and siliceous stone surfaces, walls, and rock outcrops in temperate and humid terrestrial habitats. Its dependence on stable, undisturbed stone substrates with consistent moisture levels makes it sensitive to environmental change.

Its Endangered status stems from a combination of ongoing pressures: air pollution and acid deposition degrade substrate chemistry and lichen physiology; urban development destroys or removes suitable stone surfaces; and industrial emissions introduce contaminants toxic to sensitive lichen tissues. Climate change is altering moisture regimes essential for its growth, while the loss of appropriate substrates limits colonization opportunities.

Conservation attention for this species is limited, with efforts largely folded into broader lichen and epiphyte monitoring programs, air quality regulation, and heritage stone conservation initiatives that incidentally protect suitable habitat. No targeted recovery plan is documented. Given continuing habitat loss and unresolved pollution pressures, and with population trend classified as unknown, the species' long-term trajectory remains uncertain without more focused monitoring and substrate protection.

This crustose lichen grows exclusively on calcareous stone surfaces, particularly old mortar joints, limestone walls, and historic masonry in urban and semi-urban environments. It requires stable, slightly alkaline substrates with consistent moisture levels and is typically found on north-facing walls that receive indirect light.