Oribatid mites like lichens—feeding preferences among three Cladonia species with different chemistry

Abstract Lichens in general and members of the genus Cladonia in particular are known for their repertoire of chemical substances. These substances have been attributed various roles, including a role in the defence against herbivores. Unsurprisingly, Cladonia species share habitats with many small invertebrates, like mites. Mites have been suggested to regularly feed on lichens, with potential detrimental effects for the lichen. Here we tested the feeding preferences of two oribatid mite species ( Carabodes areolatus and C. marginatus ) for three members of the lichen genus Cladonia . Cladonia coniocraea , C . norvegica and C . rubrotincta have similar morphology, ecology, and they regularly share their habitats with the selected mites, but produce different chemical compounds (barbatic acid in Cladonia norvegica , barbatic and rhodocladonic acids in Cladonia rubrotincta , and the fumarprotocetraric acid complex in Cladonia coniocraea ), some of which are considered to have antiherbivore properties. Our experiments conducted over a period of 14 days revealed that none of the three lichens was rejected as a food source. When given a choice between two different lichens, mites prefer C. rubrotincta over C. norvegica , but feed to a similar extent on C. coniocraea and C. rubrotincta . In experiments only with C. rubrotincta , which produces the red chemical compound rhodocladonic acid, a substance with suggested antiherbivore activity, mites surprisingly seem to prefer red-pigmented over unpigmented tissue.