Myco-photobiontal selection in a Mediterranean cryptogam community with Fulgensia fulgida

To examine the mode of dispersal and photobiont selectivity of Fulgensia fulgida we investigated the photobionts associated with the lichens of a community related to the Toninio-Psoretum decipientis association. Photobionts and mycobionts were analysed using morphological (light microscopy) and molecular (internal transcribed spacer (ITS) and partial large subunit (LSU) nuclear ribosomal DNA sequencing) techniques. The thalli of the mycobiont of F. fulgida, which were identical in their ITS and partial LSU-sequence, contained two strains of Trebouxia asymmetrica, one of them also present in a thallus of Toninia sedifolia. Other co-occurring lichens, namely Squamarina lentigera, Catapyrenium michelii and Collema cristatum, were shown to have Asterochloris irregularis, Myrmecia and Nostoc as photobionts. It is suggested that F. fulgida is selective in its photobiont choice, that dispersal of the lichen has occurred by way of ascospores and subsequent independent relichenization events and that F. fulgida and T. sedifolia share the same photobiont pool. The results also suggest possible mechanisms of relichenization and strategies for future research on the selectivity of lichen bionts.