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Diversification of symbiotic fungi

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Front. Microbiol. | doi: 10.3389/fmicb.2018.00283

Multiple, distinct intercontinental lineages but isolation of Australian populations in a cosmopolitan lichen-forming fungal taxon, Psora decipiens (Psoraceae, Ascomycota)

  • 1Biology & M. L. Bean Life Science Museum, Brigham Young University, United States
  • 2Museum of Evolution, Uppsala University, Sweden
  • 3Department of Biotechnology,, Iranian Research Organization for Science and Technology (IROST), Iran
  • 4Research School of Chemistry, Australian National University, Australia
  • 5University of Oslo, Norway
  • 6Science and Education, The Field Museum, United States
  • 7Plant Ecology and Systematics, Biology Institute, University of Kaiserslautern, Germany
  • 8Department of Botany, Swedish Museum of Natural History, Sweden

Multiple drivers shape the spatial distribution of species, including dispersal capacity, niche incumbency, climate variability, orographic barriers, and plate tectonics. However, biogeographic patterns of fungi commonly do not fit conventional expectations based on studies of animals and plants. Fungi, in general, are known to occur across exceedingly broad, intercontinental distributions, including some important components of biological soil crust communities (BSCs), although molecular data often reveal unexpected biogeographic patterns in lichenized fungal species that are assumed to have cosmopolitan distributions. The lichen-forming fungal species Psora decipiens is found on all continents, except Antarctica and occurs in BSCs across diverse habitats, ranging from hot, arid deserts to alpine habitats. In order to better understand factors that shape population structure in cosmopolitan lichen-forming fungal species, we investigated biogeographic patterns in the cosmopolitan taxon P. decipiens, along with the closely related taxa P. crenata and P. saviczii. We generated a multi-locus sequence dataset based on a worldwide sampling of these taxa in order to reconstruct evolutionary relationships and explore phylogeographic patterns. Both P. crenata and P. decipiens were not recovered as monophyletic; and P. saviczii specimens were recovered as a monophyletic clade closely related to a number of lineages comprised of specimens representing P. decipiens. Striking phylogeographic patterns were observed for P. crenata, with populations from distinct geographic regions belonging to well-separated, monophyletic lineages. South African populations of P. crenata were further divided into well-supported sub-clades. While well-supported phylogenetic substructure was also observed for the nominal taxon P. decipiens, nearly all lineages were comprised of specimens collected from intercontinental populations. However, all Australian specimens representing P. decipiens were recovered within a single well-supported monophyletic clade consisting solely of Australian samples. Our study supports up to ten candidate species-level lineages in P. decipiens, based on genealogical concordance and coalescent-based species delimitation analyses. Our results support the general pattern of the biogeographic isolation of lichen-forming fungal populations in Australia, even in cases where closely related congeners have documented intercontinental distributions. Our study has important implications for understanding factors influencing diversification and distributions of lichens associated with BSC.

Keywords: biogeography, Biological soil crusts (BSC), cryptic species, Disjunct populations, long-distance dispersal, Psora, semi-arid, South Africa

Received: 29 Apr 2017; Accepted: 07 Feb 2018.

Edited by:

Carlos P. Taborda, University of São Paulo, Brazil

Reviewed by:

Birinchi K. Sarma, Banaras Hindu University, India
Ram Prasad, Amity University, India
Stefano Ghignone, Istituto per la Protezione Sostenibile delle Piante (CNR), Italy
Luiz H. Rosa, Universidade Federal de Minas Gerais, Brazil  

Copyright: © 2018 Leavitt, Westberg, Sohrabi, Elix, Timdal, Nelsen, St. Clair, Williams, Wedin and Lumbsch. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Dr. Steve Leavitt, Brigham Young University, Biology & M. L. Bean Life Science Museum, 4143 LSB, Brigham Young University, Provo, 84602, UT, United States, sleavitt@fieldmuseum.org