Quantitative variation and the ecological role of vulpinic acid and atranorin in thallus of Letharia vulpina

High pressure liquid chromatography was used to determine concentrations of vulpinic acid and atranorin in the thaullus of Letharia vulpina. Vulpinic acid concentration is lowest in the old basal branches of the thallus and increases toward the young branch tips, whereas the reverse is true for atranorin. The suggested role of vulpinic acid as an anti-herbivore defense compound is supported by both this distribution of the compound and our observations that vulpinic acid acts as a feeding deterrent to certain invertebrates. No significant difference in the content of atranorin or vulpinic acid was found in lichens from microhabitats of different sunlight intensities.