Abstract Detail
Bryological and Lichenological Section/ABLS Schneider, Kevin [1], Resl, Philipp [1], Mayrhofer, Helmut [1], Spribille, Toby [1]. Did cyanobacteria drive early thallus size increases in lichens? Evidence from the origins of Placopsis (Trapeliaceae). Trapelia and Placopsis are two widespread genera of crustose and semi-foliose lichens that differ strikingly in size, with Trapelia forming minute thalli visible only with a hand lens and Placopsis forming striking “bull’s eye” rosettes easily recognizable at arm’s length. Recent molecular work has shown that Placopsis arose directly from within Trapelia on at least two occasions. Here we use new eight-locus DNA sequence and morphometric data to obtain a comparative view on the evolution of thallus, hymenial and cephalodial size in a large Trapelia-Placopsis phylogeny. Our data indicate a severalfold increase in both thallus and hymenial volume at the transition from Trapelia to Placopsis coinciding with the acquisition of a cyanobacterial photobiont. The availability of nitrogen appears to be an important limiting factor in the formation of large thalli. The cyanobacterial symbiosis may have enabled the fungal symbiont to overcome size constraints in oligotrophic environments such as acidic, rain-washed rock surfaces.
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1 - University of Graz, Institute of Plant Sciences, Holteigasse 6, Graz, Styria, 8010, Austria
Keywords:
phylogenetic comparative methods
macroevolution
Ostropomycetidae
symbiosis
lichen.
Presentation Type: Oral Paper:Papers for Sections
Session: 70
Location: Salon 10/The Shaw Conference Centre
Date: Wednesday, July 29th, 2015
Time: 4:15 PM
Number: 70011
Abstract ID:1422
Candidate for Awards:A. J. Sharp Award | 
