title: Ecological specialization in Trebouxia (Trebouxiophyceae) photobionts of Ramalina menziesii (Ramalinaceae) across six range-covering ecoregions of western North America.
abstract: • Premise of the study: Many lichens exhibit extensive ranges spanning several ecoregions. It has been hypothesized that this wide ecological amplitude is facilitated by fungal association with locally adapted photobiont strains.• Methods: We studied the identity and geographic distribution of photobionts of the widely distributed North American lichen Ramalina menziesii based on rbcL (chloroplast DNA) and nuclear ribosomal ITS DNA sequences. To test for ecological specialization, we associate photobiont genotypes with local climate and phorophyte.• Key results: Of the photobiont lineages of R. menziesii, 94% belong to a clade including Trebouxia decolorans. The remaining are related to T. jamesii. The photobionts showed (1) significant structure according to ecoregion and phorophyte species and (2) genetic associations with phorophyte species and climate.• Conclusions: Geography, climate, and ecological specialization shape genetic differentiation of lichen photobionts. One great advantage of independent dispersal of the fungus is symbiotic association with locally adapted photobiont strains.
authors.affiliation: Department of Ecology and Evolutionary Biology, University of California Los Angeles, Box 957239, Los Angeles, California 90095-7239 USA Faculty of Life and Environmental Sciences, University of Iceland, Sturlugata 7, 101 Reykjavík, Iceland Biodiversity and Conservation Biology, Swiss Federal Research Institute WSL, Zürcherstrasse 111, CH-8903 Birmensdorf, Switzerland.
authors.forename: Silke
authors.initials: S
authors.lastname: Werth
authors.affiliation: Department of Ecology and Evolutionary Biology, University of California Los Angeles, Box 957239, Los Angeles, California 90095-7239 USA Institute of the Environment and Sustainability, University of California Los Angeles, Box 951496, Los Angeles, California 90095-1496 USA.
authors.forename: Victoria L
authors.initials: VL
authors.lastname: Sork
keywords: Ramalina menziesii; Ramalinaceae; Trebouxia decolorans; Trebouxiophyceae; ecological specialization; genetic differentiation; host plant specificity; lichenized ascomycetes; phorophyte; photobiont; symbiosis