Message - 7th IAL Symposium

Lichen: from genome to ecosystem in a changing world
4B-P
(4B-P7) Submission ID: IAL0230-00002
EARLY DEVELOPMENT OF TEMPERATE FOLIOSE LICHENS ON COVER SLIPS
Anstett D. N. 1 , Larsen E. W. 2
1 Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, Canada
2 Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada
Lichen developmental biology is of special interest because at least two genomes are involved in morphogenesis.
Yet little is known about this process, in part because lichens grow slowly and are notoriously difficult
to culture in laboratory conditions. As well, most surfaces used for lichen growth have been difficult to image.
We attempt to document lichen development by placing soredia from foliose temperate lichens Parmelia sulcata
and Physcia adscendens onto plastic cover slips and growing them outdoors (in Canada 133 km north-east of
Toronto) for a period of 15 months. The cover slips allowed non-destructive imaging of live developing lichens
as well as preparation for light and electron microscopy. Only soredia seeded on cover slips in May (as opposed
to August or January) successfully developed. These samples were analyzed after 6, 10 and 15 months. Welldeveloped
attachment hyphae were seen by 6 months (November), while lobules (early lichen thallus) were
detected after 10 months. In other words they developed between November and March, Ontario, Canada’s
coldest time of the year. This adds weight to previous inferences that temperate lichens are more developmentally
competent at cold temperatures. In terms of morphology, the hyphae and lobules varied considerably between
species, raising the possibility that lichen species or at least genera may be identifiable at an early point in
the development process. Considering spatial patterns, soredia were often found in clumps. Most development
occurred on the periphery or outside of the soredial clumps. It was only after 15 months that soredia inside
clumps began to form more attachment hyphae and lobules with higher frequency. The delayed development
inside clumps suggests these soredia experience lateral inhibition or a lack of nutrients. Microscopic examination
suggested that the upper cortex forms after the lower cortex and that it forms in patches. Overall, we have shown
that foliose temperate lichens can be cultured on cover slips, presenting a method where development may
be observed in identified lichen species. The cover slip technique may be useful for a variety of culture studies
including biomonitoring for conditions conducive to lichen development.
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