The ecological role of secondary lichen substances

Considerable evidence, both direct and indirect, supports the hypothesis that many lichen secondary substances have significant ecological roles. Thus secondary chemistry may be important in determining the relative ecological success of individual lichen species and thus the structure and diversity of natural lichen communities. Primary ecological roles of secondary lichen substances can be classified into four groups: light-screen compounds, chemical weathering compounds, allelopathic compounds, (including antibiotic compounds), and anti-herbivore defense compounds.