Message - 7th IAL Symposium

The 7 th International Association for Lichenology Symposium 2012
(1I-O7) Submission ID: IAL0067-00001
PHOTOBIONT - MYCOBIONT INTERACTIONS IN THE WIDESPREAD LICHEN
CETRARIA ACULEATA
Printzen C. 1 , Domaschke S. 1 , Fernandez Mendoza F. 2
1 Botany and Molecular Evolution, Senckenberg Research Institute and Natural History Museum,
Frankfurt am Main, Germany
2 Laboratory Center, Biodiversity and Climate Research Center (BiK-F), Frankfurt am Main, Germany
The fruticose Cetraria aculeata is an extreme example of a lichen that occupies distributional ranges
across several biomes, including areas as different as e.g. the maritime Antarctic and the parameras of Central
Spain. We are currently investigating how interactions with genetically different photobionts (all belonging to
Trebouxia jamesii) may contribute to the ability of C. aculeata to colonize this diverse range of habitats. DNA sequences
from three loci for each symbiont confirm that the most important factors shaping the genetic structure
of T. jamesii are climate and a history of co-dispersal with the mycobiont. The genetic structure of the mycobiont
is best explained by an interaction of climatic and geographical factors. Most importantly, mycobionts in the
temperate region are consistently associated with a specific photobiont lineage. We therefore conclude that a
photobiont switch in the past enabled Cetraria aculeata to colonize temperate as well as polar habitats. The genetic
diversity of T. jamesii is highest in temperate regions and decreases significantly towards the Antarctic but
less pronouncedly towards the Arctic. This indicates that climatic factors may determine which photobionts are
available in a certain habitat but have a minor effect on the overall diversity of photobiont populations. Hence,
the low genetic diversity of photobionts and mycobionts observed in Antarctic populations of C. aculeata is
most likely not the result of increased selection pressure but of founder events during colonisation. Especially
in largely asexual lichens such as C. aculeata isolation by distance is probably not the only cause of genetic
structure. Rare photobiont switches that associate the mycobiont with locally adapted photobionts may also lead
to genetic isolation between populations and eventually to ecological specialisation and speciation.
(1I-O8) Submission ID: IAL0228-00001
GENE MOVEMENT IN THE PHOTOBIONT OF RAMALINA MENZIESII
Werth S. 1 , Sork V.L. 2
1 Biodiversity and Conservation Biology, WSL, Birmensdorf, Switzerland
2 Ecology and Evolutionnary Biology, University of California, Los Angeles, United States
Ramalina menziesii is a widespread lichen throughout coastal and slightly inland regions of western
North America in ecosystems that include desert, chaparral, oak woodland, and coniferous forest. Previously, we
have found that the fungal species survived the Pleistocene glaciations in multiple refugia. Here, we assess geographic
genetic variation in the photobiont of R. menziesii based on DNA sequence data of the nuclear ribosomal
rDNA gene cluster and the rbcL gene located on the chloroplast to address three objectives. First, we investigate
the spatial distribution of photobiont clades across the range of R. menziesii. Second, we test whether the refugial
areas found for R. menziesii fungal genotypes show the characteristics of refugial areas in its photobiont as
well (private haplotypes, high haplotype diversity). Third, we test if genetic diversity in the photobiont correlates
with latitude, and with the diversity of the mycobiont. Our results indicate that the photobiont has much greater
genetic differentiation across sites than the mycobiont and that the geographic patterns of genetic variation are
only loosely associated with that of the photobiont. Our study provides valuable insight whether the movement
of genes of lichen fungi and their photobionts exhibits congruent patterns.
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