Forest Successional Stage Affects the Cortical Secondary Chemistry of Three Old Forest Lichens

Abstract

Three epiphytic old forest lichens (Usnea longissima, Pseudocyphellaria crocata, and Lobaria pulmonaria) were transplanted along a natural shade-sun gradient comprising three successional stages in boreal spruce forests (dense young forest, open old forest, and clear-cut) for one summer. After harvest, extractable secondary compounds were analyzed by high-performance liquid chromatography, and the brown pigmentation in melanic species was quantified by reflectance measurements. Cortical compounds in all species increased from shady young forests to exposed clear-cuts. Usnic acid, the major cortical, secondary compound in U. longissima, showed consistently higher concentration in the clear-cut than in the two forested stands. Pseudocyphellaria crocata and L. pulmonaria, lacking extractable secondary compounds in the cortex, significantly increased their amounts of cortical melanins in well-lit stands. The medullary compounds showed more complex responses. Many were not influenced by environmental conditions during the transplantation, whereas the majority of those that responded showed the lowest concentration in clear-cut transplants. Only a few medullary compounds showed the highest concentration in the clear-cut, and at a low level of significance. The synthesis of UV-B-absorbing usnic acid and melanins seems to be part of an acclimation to increased light exposure. The medullary compounds in studied species barely function as solar screens despite their strong UV-B absorbance.

Spatial mapping of lichen specialized metabolites using LDI-MSI: chemical ecology issues for Ophioparma ventosa

“…The reproductive structures are often reported to produce specific lichen compounds or known to be more concentrated in phenols than the remaining thallus13, in accordance with the optimal defense theory114. Haemoventosin belongs to a structural class (quinones) exerting a wide array of biological activities of ecological significance including antibiotic, antifungal15 and cytotoxic properties10.…”

Mollusc grazing limits growth and early development of the old forest lichen Lobaria pulmonaria in broadleaved deciduous forests

“…Whether this depends on abiotic/biotic factors or diVerences between genotypes is not known. However, transplanting the species along a natural shade-sun gradient did not inXuence the content of these compounds diVerently (McEvoy et al 2007;Nybakken et al 2007), suggesting a constitutive type of defence.…”

“…Our study shows that lichen depsidones deter indigenous mollusc grazing of lichens also in natural forest ecosystems. The content of medullary depsidones in mature L. pulmonaria seems to vary between diVerent populations, or even within populations (McEvoy et al 2007;Nybakken et al 2007). Whether this depends on abiotic/biotic factors or diVerences between genotypes is not known.…”

Removal of secondary compounds increases invertebrate abundance in lichens

“…The combined supernatants were evaporated to dryness and dissolved in 1000e2000 ml acetone. The extracted compounds were then quantified by HPLC using an ODS Hypersil column, 50 Â 4.6 mm using 0.25% orthophosphoric acid and 1.5% tetrahydrofuran in Millipore (Millipore, Billerica, Massachusetts, USA) water (A) and 100% methanol (B) as mobile phases at 2 ml min À1 , and UV detection at 245 nm (following Nybakken et al, 2007). Compound identification was based on retention times, online UV spectra and co-chromatography of commercial standards.…”