The Lichenologist 36(6): 381–390 (2004)  2004 The British Lichen Society DOI: 10.1017/S002428290401477X Printed in the United Kingdom Genetic diversity in Xanthoria parietina (L.) Th. Fr. (lichen-forming ascomycete) from worldwide locations Rosmarie HONEGGER, Undine ZIPPLER, Sandra SCHERRER and Paul S. DYER Abstract: Specimens of Xanthoria parietina were collected from worldwide locations and ascospore discharge used to establish axenic cultures of the mycobiont. DNA was extracted and RAPD-PCR fingerprinting of 59 isolates was successfully achieved, resulting in 58 unique fingerprints. 110 multilocus RAPD markers were generated and used to construct a dendrogram. Two main groups were distinguished (75% bootstrap support): the first comprising samples from the Iberian Peninsula, the Balearic and Canary Islands; the second comprising all other worldwide samples including isolates from throughout Europe and North America. Samples from Australia and New Zealand clustered with the second group except one additional, phenotypically distinct specimen, not belonging to X. parietina, which formed an outgroup. However, comparative DNA sequence analyses are required to verify this interpretation. Key words: genetic diversity, lichen, population biology, RAPD-PCR, Xanthoria Introduction Xanthoria parietina is one of the most com- mon and widespread lichen species in Europe. It forms characteristic golden yellow thalli that occur on a wide range of natural and anthropogenic substrata, and are found at shaded through to fully sunlit sites. It is relatively toxitolerant and nitrophilous and is often found at eutrophicated sites. The area of distribution ranges from the Caucasus to westernmost Europe. The species is also common on the east coast of northern North America, and it occurs on the west coast from Baja California to the southern part of British Columbia (Lindblom 1997; Brodo et al. 2001; McCune 2004). In addition X. parietina has been reported from Australia and New Zealand where it is assumed to be an introduced species (Galloway 1985; Rogers 1992). Xanthoria parietina forms no vegetative symbiotic propagules but is invariably fertile; its central thalline areas being covered by apothecia. The presence of abundant apoth- ecia of all developmental stages distinguishes this species from X. calcicola and X. ectane- oides. Most authors assume X. parietina to disperse exclusively via ascospores, which have to re-lichenize (Ott 1987). However, vegetative dispersal via thallus fragments has also been shown to occur (Honegger 1996; Honegger et al. 1996). Dispersal by grazing invertebrates, especially lichenivorous mites (Acari) whose faecal pellets have been shown to contain viable ascospores and photobiont cells of X. parietina, might, in addition, be more common than previously assumed (Meier et al. 2002). Such lichenivorous mites are hypothesized to be very efficient vectors for short- and long-distance dispersal of X. parietina and its unicellular photo- autotrophic partner Trebouxia sp. The role of migratory birds carrying lichenivorous mites and/or their faecal pellets over long R. Honegger, U. Zippler and S. Scherrer: Institute of Plant Biology, University of Zürich, Zollikerstrasse 107, CH-8008 Zürich, Switzerland. P. S Dyer: School of Biology, University of Nottingham, University Park, Nottingham NG7 2RD, UK.