The frozen journey of a lichen: Dispersal and local adaptation of Thamnolia vermicularis

Ioana Onut BRÄNNSTRÖM (Uppsala): The process of lichenization enabled two organisms to conquer habitats with extreme conditions like arctic tundra or deserts. The lichen Thamnolia vermicularis is found in many arctic and alpine localities all over the world. Its distribution in Sweden is particularly interesting because it also grows on the two southern islands Öland and Gotland (on alvars). Like in many other lichens the species biology is not fully understood. No sexual spores were found and therefore it is assumed that it reproduces and disperses by fragments (when both symbiotic partners are dispersed simultaneously) or by fungal asexual spores and therefore relichenization needs to occur. The fact that the species seems to spread only clonal makes its extraordinary worldwide distribution puzzling. In a pilot study of the life history of T. vermicularis we found that the fungal component exhibits an impressive amount of genetic diversity on Öland, Gotland or in Romania. This was in contrast with the samples from Northern Sweden, Norway, Iceland or Alaska which were found to be highly clonal. The study also revealed that in different localities the fungal partner of T. vermicularis is associated with diverse algal strains or species from Trebouxia sp. I will talk about the influence of the Last Glacial Period on the species T. vermicularis. I hypothesize about its migration patterns, its dispersal and adaptation strategies.