title: Cryptic diversity and symbiont interactions in rock-posy lichens.
abstract: Identifying factors that influence species interactions is central to research in symbiotic systems. While lichens represent iconic models of symbiosis and play important roles in understanding the biology of symbiotic interactions, patterns of interactions in lichen symbionts and mechanisms governing these relationships are not well characterized. This is due, in part to the fact that current taxonomic approaches for recognizing diversity in lichen symbionts commonly fail to accurately reflect actual species diversity. In this study, we employed DNA-based approaches to circumscribed candidate species-level lineages in rock-posy lichen symbionts (mycobiont=Rhizoplaca s. lat. species; photobiont=Trebouxia species). Our results revealed a high degree of cryptic diversity in both the myco- and photobionts in these lichens. Using the candidate species circumscribed here, we investigated the specificity of the symbionts toward their partners and inferred the relative importance of various factors influencing symbiont interactions. Distinct mycobiont species complexes, ecozones, and biomes are significantly correlated with the occurrence of photobiont OTUs, indicating that complex interactions among mycobiont lineages, ecogeography, and microhabitat determine interactions between photobionts and their mycobionts in lichen symbiosis. One-to-one specificity between mycobiont and photobiont species was not found, with the exception of R. maheui that associated with a single Trebouxia OTU that was not found with other Rhizoplaca s. lat. species. We estimated the most recent common ancestor of the core Rhizoplaca group at c. 62.5Ma, similar in age to the diverse parmelioid core group in the well-studied family Parmeliaceae. However, in contrast to Parmeliaceae, species in Rhizoplaca were found to associate with a narrow range of photobionts. Our study provides important perspectives into species diversity and interactions in iconic lichen symbiotic systems and establishes a valuable framework for continuing research into rock-posy lichens.
authors.affiliation: Science & Education, The Field Museum, Chicago, IL, USA. Electronic address: sleavitt@fieldmuseum.org.
authors.forename: Steven D
authors.initials: SD
authors.lastname: Leavitt
authors.affiliation: Department of Botany, Kasetsart University, Bangkok 10900, Thailand.
authors.forename: Ekaphan
authors.initials: E
authors.lastname: Kraichak
authors.affiliation: Faculty of Environmental Sciences, Czech University of Life Sciences Prague, Kamýcká 1176, Praha 6, Suchdol, Czech Republic.
authors.forename: Jan
authors.initials: J
authors.lastname: Vondrak
authors.affiliation: Geological Sciences, Stanford University, Stanford, CA, USA.
authors.forename: Matthew P
authors.initials: MP
authors.lastname: Nelsen
authors.affiliation: Department of Biotechnology, Iranian Research Organization for Science and Technology, Tehran, Iran.
authors.forename: Mohammad
authors.initials: M
authors.lastname: Sohrabi
authors.affiliation: Real Jardín Botánico (CSIC), 28014 Madrid, Spain.
authors.forename: Sergio
authors.initials: S
authors.lastname: Perez-Ortega
authors.affiliation: Department of Biology and M.L. Bean Life Science Museum, Brigham Young University, Provo, UT 84602, USA.
authors.forename: Larry L
authors.initials: LL
authors.lastname: St Clair
authors.affiliation: Science & Education, The Field Museum, Chicago, IL, USA.
authors.forename: H Thorsten
authors.initials: HT
authors.lastname: Lumbsch
mesh_terms: D044822:Biodiversity; D000460:Chlorophyta / Q000145:classification / Q000502:physiology*; D004271:DNA, Fungal / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D008011:Lichens / Q000145:classification / Q000235:genetics / Q000502:physiology*; D010802:Phylogeny; D017422:Sequence Analysis, DNA; D013559:Symbiosis
chemical_list: D004271:DNA, Fungal
keywords: Ecoregion; Lecanoraceae; Selectivity; Specificity; Symbiosis; Trebouxia