Life history and migration pattern of the lichen Thamnolia vermicularis
Ioana Onuţ Brännström
Lichens are complex organisms, often called by lichenologists miniature ecosystems. They are made of two primary partners, a mycobiont (a fungus) and photobionts (algae or/and cyanobacteria). In addition they also have parasymbionts (bacteria, parasitic fungi, viruses).
However the general trend is to look only at one of the partners of the symbiosis; the mycobiont in particular. However, this evolutionary relationship has to be seen as a whole, as a unique entity. The age of genetics and molecular biology opens new doors and gives the opportunity for a contemporary way to study them.
The worm lichen, Thamnolia vermicularis has fascinated lichenologists for a long time. It is not only the appearance that makes it spectacular (it looks like a dry white worm) but also its life cycle, morphology and its dispersal. The genus has two chemotypes: one producing squamatic and baemoycesic acid (yellowish under UV light) and one thamnolic acid (reddish under UV light). In the field they are indistinguishable but some believes that the two chemical races represent different species. It can be found in many arctic and alpine localities all over the world. Sweden is a special case: here, except for the mountains, it is also growing on two southern islands Öland and Gotland, in alvar areas.
In my master degree project about this lichen species, I found out that in the islands Öland and Gotland the fungal component of T. vermicularis exhibits an impressive amount of genetic diversity. This result was in strong contrast to samples from Northern Sweden and Iceland, which were found to be highly clonal. My results also indicated that the lichen has been dispersed to Northern Sweden after the last ice age, and that no ice age refugia, where it might have survived during the ice age, were present. My study also revealed that the fungal partner of T. vermicularis is associated in different localities with different algal strains or species, suggesting that algal switching is a means by which lichens are adapting to new environments.
Degree project in biology, Master of science (2 year), 2012 Examensarbete i biologi 45 hp till magisterexamen, 2012
Biology Education Centre, Dept of Ecology and Genetics, and Dept of Organismal Biology, Uppsala University
Supervisors: Hanna Johannesson and Leif Tibell
