Organisms Diversity & Evolution

, Volume 16, Issue 3, pp 497–524

Evaluation of traditionally circumscribed species in the lichen-forming genus Usnea, section Usnea (Parmeliaceae, Ascomycota) using a six-locus dataset

  • Kristiina Mark
  • Lauri Saag
  • Steven D. Leavitt
  • Susan Will-Wolf
  • Matthew P. Nelsen
  • Tiiu Tõrra
  • Andres Saag
  • Tiina Randlane
  • H. Thorsten Lumbsch
Original Article

DOI: 10.1007/s13127-016-0273-7

Cite this article as:
Mark, K., Saag, L., Leavitt, S.D. et al. Org Divers Evol (2016) 16: 497. doi:10.1007/s13127-016-0273-7

Abstract

Recent taxonomic and DNA sequence-based studies in several groups of lichen-forming fungi have revealed incongruence between the morphological and molecule-based circumscriptions of species. While the cosmopolitan genus Usnea is well-known and easily recognized by the yellowish beard-like thallus with central cord, delimitation of many Usnea species is difficult due to the high variation and complexity of diagnostic characters. In this study, we assessed the monophyly of 18 species from section Usnea occurring in North America and Europe, including sorediate and sexually reproducing taxa with both pendent and shrubby thalli. Six nuclear markers (ribosomal internal transcribed spacer (ITS) and intergenic spacer (IGS), and protein-coding beta-tubulin, MCM7, RPB1 and RPB2) were sequenced for 144 samples. All analyzed loci show weak genetic structure and short branch lengths in single-locus topologies, suggesting recent diversification history of the sampled taxa. Concatenated, multi-locus analyses conducted in Bayesian and maximum likelihood frameworks, as well as coalescent-based species delimitation and species tree methods, recover several distinct clades, some represent traditional morphology-based species (Usnea cavernosa, U. praetervisa, U. silesiaca, U. wasmuthii), while others form clusters of two or more species (Usnea floridaU. subfloridana, U. fulvoreagensU. glabrescens, U. barbataU. chaetophoraU. dasopogaU. diplotypus, U. barbataU. intermediaU. lapponicaU. substerilis). We propose synonymization of U. substerilis under U. lapponica. The status of several other species within intermixed clusters requires further evaluation with more extensive sampling and the inclusion of more variable markers before taxonomic consequences can be considered. A new species, Usnea parafloridana is described from Wisconsin, USA.

Keywords

Lichenized fungi Rapid radiation Species delimitation Species trees Taxonomy Usnea 

Supplementary material

13127_2016_273_MOESM1_ESM.pdf (339 kb)
Online Resource 1Fig. S1–S6 Majority rule consensus trees inferred from ML analysis on ITS (Fig. S1), IGS (Fig. S2), beta-tubulin (Fig. S3), MCM7 (Fig. S4), RPB1 (Fig. S5) and RPB2 (Fig. S6) datasets together with nonparametric bootstrap support (BP) and posterior probability (PP) values from Bayesian inference. Above branch is indicated ML bootstrap probabilities (BP) and below Bayesian posterior probability (PP) scores. Branches marked in bold indicate strong support (BP ≥ 70 and PP ≥ 0.95) for specified clade. Scale bar shows the number of substitutions per site (PDF 339 kb)
13127_2016_273_MOESM2_ESM.pdf (136 kb)
Online Resource 2Fig. S7 Majority rule consensus tree of all available Usnea fulvoreagens, U. glabrescens s.str. and U. pacificana sequences (Table 1) with U. silesiaca as an outgroup, based on six concatenated loci, inferred in RAxML. Clade bootsrap probabilites (BP) are given above branch and strongly supported clades (BP ≥ 70 %) are marked in bold. Scale bar shows the number of substitutions per site. In brackets are given specimen code, country, and secondary chemistry. Secondary metabolites in fulvoreagens-glabrescens clade: bar − barbatic acid; BMY − baeomycesic acid; NSTI − norstictic acid; pro − protocetraric acid; SAL − salazinic acid; SQU − squamatic acid; STI-comp − stictic acid complex with connorstictic cryptostictic acids; unid rfcl x − unidentified substance from reference class x. Capital letters denotes major compounds in chemotype, lower case accessory substances (PDF 136 kb)
13127_2016_273_MOESM3_ESM.pdf (274 kb)
Online Resource 3Fig. S8 Majority rule consensus tree of all studied Usnea parafloridana specimens with some representatives from florida-subfloridana and wasmuthii clades, based on six concatenated loci, inferred in RAxML. Clade bootsrap probabilites (BP) are given above branch and strongly supported clades (BP ≥ 70 %) are marked in bold. Scale bar shows the number of substitutions per site. In brackets are given specimen codes and secondary chemistry. Secondary metabolites in U. parafloridana: NSTI − norstictic acid; SAL − salazinic acid; unid rfcl x − unidentified substance from reference class x. Capital letters denotes major compounds in chemotype, lower case accessory substances (PDF 274 kb)
13127_2016_273_MOESM4_ESM.pdf (1.4 mb)
Online Resource 4Fig. S9 Examples of lichen substances of some studied Usnea specimens, incl. U. parafloridana sp. nov., identified in thin layer chromatography analyses. Secondary metabolites are visualized in solvent system A, after treatment with sulphuric acid and heating (Orange et al. 2001). Identified secondary metabolites: al – alectorialic acid; bar − barbatic acid; bmy − baeomycesic acid; cnsti – connorstictic acid; csti – cryptostictic acid; nsti – norstictic acid; sal – salazinic acid; squ − squamatic acid; sti – stictic acid; tha – thamnolic acid; usn − usnic acid (PDF 1398 kb)

Copyright information

© Gesellschaft für Biologische Systematik 2016

Authors and Affiliations

  • Kristiina Mark
    • 1
  • Lauri Saag
    • 2
  • Steven D. Leavitt
    • 3
  • Susan Will-Wolf
    • 4
  • Matthew P. Nelsen
    • 5
  • Tiiu Tõrra
    • 6
  • Andres Saag
    • 1
  • Tiina Randlane
    • 1
  • H. Thorsten Lumbsch
    • 3
  1. 1.Institute of Botany and EcologyUniversity of TartuTartuEstonia
  2. 2.Department of Evolutionary BiologyEstonian BiocentreTartuEstonia
  3. 3.Science and EducationThe Field MuseumChicagoUSA
  4. 4.Estonia Department of BotanyUniversity of Wisconsin-MadisonMadisonUSA
  5. 5.Department of Geological SciencesStanford UniversityStanfordUSA
  6. 6.Estonian Marine InstituteUniversity of TartuTallinnEstonia

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