Message - 7th IAL Symposium

The 7 th International Association for Lichenology Symposium 2012
(2I-P3) Submission ID: IAL0140-00005
A TALE OF TWO MYCOBIONTS: EXPLORING CONVERGENT EVOLUTION AND
PHOTOBIONT SWITCHING IN THE LICHEN GENUS POLYCHIDIUM
Muggia L. 1 , Spribille T. 2
1 Institute of Plant Science, University of Graz, Graz, Austria
2 Division of Biological Sciences, University of Montana, Missoula, Montana, United States
The cyanolichen genus Polychidium (Ach.) Gray is generally considered to consist of four species,
one being muscicolous, the others epiphytes. The four species share strikingly similar gross morphology but
consort with different photobiont genera, namely Nostoc and Scytonema. In the past, thallus architecture has
been a powerful guide in classification of lichen genera such as Polychidium and has often been taken to trump
photobiont association and ascocarp type, but the reliability of these characters to predict phylogenetic affinity
has seldom been tested. We tested the monophyly of Polychidium with a multilocus phylogeny based on nuclear
and mitochondrial sequence data from all known Peltigeralean families, and reconstructed ancestral states for
specific thallus architecture and ascoma ontogeny types relative to Polychidium and other clades. Our working
hypothesis was that if Polychidium were found to be monophyletic, it would suggest photobiont switching
among closely related species. If however species were found to arise in different lineages, this would suggest
convergent body plan and ascoma type evolution. We found that Polychidium consists of two species groups
that arose independently in different suborders within the Peltigerales, associated with Nostoc and Scytonema
photobionts, respectively. We infer from ancestral character state reconstruction that dendroid thallus architecture
evolved independently in these two lineages. The independent development of similar dendroid thallus architecture
in different fungal suborders with different photobionts represents one of the most extreme examples
of convergent evolution documented to date in symbiotic organisms.
(2I-P4) Submission ID: IAL0141-00001
ON THE SPECIATION PROCESS IN MORPHOSPECIES:
THE EXAMPLE OF PARMELINA PASTILLIFERA
Nuñez J. 1 , Divakar P. K. 1 , Cubas P. 1 , Crespo A. 1
1 Biología Vegetal II, Univ. Complutense of Madrid, Madrid, Spain
The independence of the morphospecies Parmelina pastillifera is not questioned currently although it
had been debated by authors which considered this taxon either as a synonymous with P. tiliacea, or as a variety
of that species or as a different species. Parmelina pastillifera presents morphological characteristic button-like
stalked isidia and grows in relatively humid oceanic regions in Europe whereas P. tiliacea has cylindrical isidia
and grows in drier areas and shows a wider geographic distribution in Eurasia, Macaronesia and North Africa.
Previous molecular phylogenetic studies have shown both taxa as sister species, although few individuals have
been studied so far. The finding of individuals with intermediate morphology poses some doubts on the relationship
between these taxa and their taxonomic status. Analyses with three molecular markers (nuITS, mtLSU and
Elongation Factor 1), on an extensive population sampling from different localities in Western Europe, show that
both species are genetically close. However the relationships between P. pastillifera and P. tiliacea cannot be
directly established concatenating the three molecular markers, due to incongruence in the phylogenetic signals
and the sharing of common haplotypes in the three markers. We here present an attempt to reconcile the set of
gene trees with a shared species tree, using a coalescent model in order to gain a deep insight into their genetic
relationships and their taxonomic status in the perspective of a speciation process.
95
2I-P