Message - 7th IAL Symposium

The 7th International Association for Lichenology Symposium 2012
4B: Lichen symbionts and ecophysiology
(4B-O1) Submission ID: IAL0174-00002
ON TIME OR ‘FASHIONABLY’ LATE ? THE COMPARATIVE DATING OF LICHEN-ASSOCIATED
EUKARYOTIC ALGAE AND THEIR FUNGAL SYMBIONTS
Nelsen M. P. 1 , Lücking R. 2 , Andrew C. J. 2 , Ree R. 2
1 Committee on Evolutionary Biology, Department of Botany, University of Chicago, Field Museum,
Chicago, Illinois, United States
2 Department of Botany, The Field Museum, Chicago, United States
How do symbiotic associations originate and evolve? Determining when associations originated, both
in time and relative to the diversification of their interacting lineages, can inform about whether certain earth history
events are associated with the initiation of these associations and also if transitions were contemporaneous
with the evolution of an interacting lineage. Furthermore, it can shed light on the role (if any) a lineage plays
in the diversification of its interacting lineage. Previous models have been put forward suggest that in contemporaneous
or near contemporaneous originations, the diversification of one lineage is expected to have some
impact on the evolution of its interacting lineage; contrastingly, in symbioses with largely asynchronous origins
of interacting lineages, the factors driving the diversification of these interacting lineages are expected to be
unrelated. Here we focus on providing a timeline for the diversification of lichen-associated eukaryotic algae, by
assembling a dataset consisting of 18S and rbcL sequence data and employing a relaxed molecular clock approach,
utilizing several fossil calibration points. Stem and crown ages for a number of algal lineages associating
with lichen-forming fungi were obtained, and this is related to the evolution of their fungal partners.
(4B – O2) Submission ID: IAL0112-00001
PHYLOGEOGRAPHY AND GENETIC STRUCTURE OF DICTYOCHLOROPSIS RETICULATA
ASSOCIATED WITH LOBARIA PULMONARIA, L. IMMIXTA AND L. MACARONESICA
IN MACARONESIA.
Cheenacharoen S. 1 , Dal Grande F. 1 , Werth S. 1 , Scheidegger C. 1
1 Biodiversity and Conservation Biology, Swiss Federal Research Institute WSL, Birmensdorf, Switzerland
Macaronesia is a group of archipelagos in the North-East Atlantic Ocean near Europe and North Africa,
which currently represents the largest laurel forests (laurisilva). These forests host a high diversity of habitats
and species, many of which are endemic. Two laurisilva-associated lichens, Lobaria immixta and L. macaronesica,
and the widely distributed L. pulmonaria share the same habitats and depend on the same photobiont
species, Dictyochloropsis reticulata. We examined almost four thousand thalli from 12 islands on the archipelagos
of Azores, Canary Islands and Madeira, using 13 alga-specific highly variable microsatellite loci. Discriminant
analysis of principal component (DAPC), measures of genetic differentiation (DEST, FST), and Bayesian
analyses detected two well differentiated groups, namely populations from Azores vs. populations from Canary
Islands and Madeira. Spatial autocorrelation and other evidence indicated the absence of gene flow between
the groups. These two regions were also comparably rich in geographically restricted alleles, representing a
worldwide hot spot for the genetic diversity of D. reticulata. We also found that there was no partitioning of algal
genetic structure related to the fungal host. This study provides new insights on the level of diversification of
symbiotic green algae, as result of a radiation-like diversification on oceanic islands. Our findings support the
hypothesis of a functional green algal-mediated guild, for which the Lobariacean fungi of the studied ecosystem
are horizontally linked through sharing of photobiont genotypes.
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4B-O