Message - 7th IAL Symposium

Lichen: from genome to ecosystem in a changing world
2I-O
(2I-O3) Submission ID: IAL0072-00001
DEVELOPMENT OF THALLUS AXES IN USNEA LONGISSIMA, A FRUTICOSE LICHEN
SHOWING DIFFUSE GROWTH
Sanders W. B. 1 , De Los Rios A. 2
1 Biological Sciences, FGCU, Ft. Myers, Florida, United States
2 Museo Nacional de Ciencias Naturales, CSIC, Madrid, Spain
Cell wall thickening in plants is generally limited to tissues that have ceased growth. But fungal tissues
in at least two lichens are known to undergo extensive diffuse growth despite massively thickened cell walls.
We examined Usnea longissima (recently shown to elongate diffusely -- Rolstad & Rolstad 2008) in order to
determine how diffuse growth shapes the morphological development of thallus axes, and how the thick cell walls
of the medullary cord behave in diffuse growth. Material was examined using light microscopy, epifluorescence
microscopy, SEM and TEM. Development of long axes involved continued diffuse growth of the central medullary
cord, resulting in destruction of the overlying cortex, disruption of the algal layer, and stimulation of profuse
lateral branch formation. At the anatomical level, fungal cells of the medullary cord repeatedly deposit layered,
electron-dense wall materials that include UV-epifluorescent components, and amorphous electron-transparent
substances. As older wall materials accumulate peripherally, discontinuities appear in the electron-dense layers
and new branch cells grow right through the older wall layers. Layered cell wall accumulations were similar to
those observed previously in Ramalina menziesii, although somewhat less extensive and with a greater proportion
of electron-dense/UV-epifluorescent components.
(2I-O4) Submission ID: IAL0140-00001
THE TEPHROMELA ATRA SPECIES-COMPLEX: A CASE STUDY OF SYMBIOTIC SPECIES
EVOLUTION
Muggia L. 1 , Spribille T. 2 , Perez-Ortega S. 3 , Grube M. 1
1 Institute of Plant Science, University of Graz, Graz, Austria
2 Division of Biological Sciences, University of Montana, Missoula, United States
3 Department of Environmental Biology, Museo Nacional de Ciencias Naturales, Madrid, Spain
Tephromela atra is a cosmopolitan lichen species, which grows on different substrates and in different
climatic conditions. It moreover exhibits a high degree of morphological heterogeneity. T. atra is therefore often
seen as an unresolved species complex with difficult and controversial taxonomic interpretation of its infraspecific
taxa. New species of the genus Tephromela (described from the Americas and the Southern Hemisphere in
the last two decades) differ slighthly by chemical or morphological characters from European T. atra. A previous
phylogenetic study of samples from the Mediterranean revealed the presence of diverse lineages of both the
mycobiont and the photobiont partners. We expanded our ongoing work on the T. atra species-complex to
include specimens from the whole range of its geographic distribution. We perform molecular and chemical
analyses and culture experiments assess geographic distribution of genetic diversity and adaptation to climatic
conditions of mycobionts and photobionts in the T. atra species complex. Our preliminary results show that
saxicolous T. atra are chemically homogeneous, although they represent distinct haplotype groups. We found
genetic divergence between cold regions or higher elevation and lower elevations and warmer climate. Corticolous
Tephromela samples segregate in separate clades. T. atra associates with green photobionts belonging
to six different Trebouxia clades. The wider sampling confirms that specimens from higher elevation and
colder region associate preferentially with T. simplex, whereas the most common photobionts still undescribed
Trebouxia sp. 1 and sp. 2, seem not to be restricted only to the Mediterranean region but occur also in the Northern
Europe, Chile and Peru.
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