Abstrakt
In our study we tested the hypothesis that acetone-extractable compounds protect selected epiphytic species of the Parmeliaceae family against lichenivorous molluscs. We chose 6 species with diverse secondary compounds - Parmelia sulcata, P. saxatilis, Melanelixia fuliginosa, M. subaurifera, M. glabra, Parmelina tiliacea and 2 species with no secondary metabolites detected by t.l.c.(Smith et al. 2009) - Melanohalea exasperatula and M. exasperata.
Two species of molluscs with different ecological strategies were selected - Lehmannia marginata and Cochlodina cerata. Following the method of Solhaug and Gauslaa (2001) for acetone-rinsing and adjusting the design of Gauslaa (2005) we set an experiment - lichen thalli were cut into two halves and one of them was rinsed in acetone.
The two halves were put in each of ten glass containers together with two individuals of a mollusc species. The same procedure was used for all the lichen-mollusc species combinations.
Afterwards the amount of thallus consumed was calculated. A strong preference for the acetone-rinsed thallus part was observed for all the species containing secondary lichen compounds.
The results are reliable at p<0.05. There was no preference between thallus parts in M. exasperatula.
Lichen species rarely found with grazing marks in the field (e.g. P. saxatilis) were palatable after the acetone-treatment.
Moreover, species grazed fre-quently in the field became even more attractive. Thus, the anti-herbivore effect of secondary metabolites in lichens has been demonstrated.
Differences in preference for the acetone-extracted part as well as the ability to feed on the untreated part were observed between the lichen species.