AUTHOR=Medeiros Ian D. , Mazur Edyta , Miadlikowska Jolanta , Flakus Adam , Rodriguez-Flakus Pamela , Pardo-De la Hoz Carlos J. , Cieślak Elżbieta , Śliwa Lucyna , Lutzoni François 

TITLE=Turnover of Lecanoroid Mycobionts and Their Trebouxia Photobionts Along an Elevation Gradient in Bolivia Highlights the Role of Environment in Structuring the Lichen Symbiosis

JOURNAL=Frontiers in Microbiology

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2021.774839

DOI=10.3389/fmicb.2021.774839

ISSN=1664-302X

ABSTRACT=<p>Shifts in climate along elevation gradients structure mycobiont–photobiont associations in lichens. We obtained mycobiont (lecanoroid Lecanoraceae) and photobiont (<italic>Trebouxia</italic> alga) DNA sequences from 89 lichen thalli collected in Bolivia from a ca. 4,700 m elevation gradient encompassing diverse natural communities and environmental conditions. The molecular dataset included six mycobiont loci (ITS, nrLSU, mtSSU, <italic>RPB1</italic>, <italic>RPB2</italic>, and <italic>MCM7</italic>) and two photobiont loci (ITS, <italic>rbc</italic>L); we designed new primers to amplify Lecanoraceae <italic>RPB1</italic> and <italic>RPB2</italic> with a nested PCR approach. Mycobionts belonged to <italic>Lecanora</italic> s.lat., <italic>Bryonora</italic>, <italic>Myriolecis</italic>, <italic>Protoparmeliopsis</italic>, the “<italic>Lecanora</italic>” <italic>polytropa</italic> group, and the “<italic>L</italic>.” saligna group. All of these clades except for <italic>Lecanora</italic> s.lat. occurred only at high elevation. No single species of Lecanoraceae was present along the entire elevation gradient, and individual clades were restricted to a subset of the gradient. Most Lecanoraceae samples represent species which have not previously been sequenced. <italic>Trebouxia</italic> clade C, which has not previously been recorded in association with species of Lecanoraceae, predominates at low- to mid-elevation sites. Photobionts from <italic>Trebouxia</italic> clade I occur at the upper extent of mid-elevation forest and at some open, high-elevation sites, while <italic>Trebouxia</italic> clades A and S dominate open habitats at high elevation. We did not find <italic>Trebouxia</italic> clade D. Several putative new species were found in <italic>Trebouxia</italic> clades A, C, and I. These included one putative species in clade A associated with <italic>Myriolecis</italic> species growing on limestone at high elevation and a novel lineage sister to the rest of clade C associated with <italic>Lecanora</italic> on bark in low-elevation grassland. Three different kinds of photobiont switching were observed, with certain mycobiont species associating with <italic>Trebouxia</italic> from different major clades, species within a major clade, or haplotypes within a species. Lecanoraceae mycobionts and <italic>Trebouxia</italic> photobionts exhibit species turnover along the elevation gradient, but with each partner having a different elevation threshold at which the community shifts completely. A phylogenetically defined sampling of a single diverse family of lichen-forming fungi may be sufficient to document regional patterns of <italic>Trebouxia</italic> diversity and distribution.</p>