Suggested citation for this web site:

Randlane, T., Tõrra, T. & Saag, A. 2008. An interactive key to the reliably reported Usnea species in Europe. – Last update: January 6, 2009.

The beeta version of this key was uploaded just a few days before the IAL6 meeting in Asilomar, in July 2008. The key was briefly introduced during the meeting and everyone interested was asked to test the practical identification of Usnea species using this tool. By now some feedback has been received and many changes/corrections carried out. Further suggestions are highly appreciated (click the button ‘Contact on the front page and send an e-mail to the authors).


The number of species in genus Usnea varies from 300–600, according to different authors. The exact number of Usnea species in Europe is not known either due to difficulties in identification and numerous taxonomic uncertanties at the species level. We analysed ca 30 lichen checklists and floras of European countries published during the last 15 years (see below), and compiled the list of Usnea species, reliably recorded in Europe. The list presently includes 31 Usnea species, and probably will increase in the future.

An interactive key for these 31 Usnea species was compiled within an EU project KeyToNature ( The key was on purpose built up on possibly easy characters/combinations of characters to offer identification help also to the non-specialists. The authors admit that such simplification can cause misidentifications in more complicated cases.

Instructions for using the interactive key

  • All keys are entirely dichotomous, i.e. at every step you have to decide between the two options. To select an option, click on the corresponding statement (text on the blue background).
  • At every step of identification you can either go back for one step or start again from the very beginning by clicking the according buttons (‘go back’ or ‘start again’).
  • When the identification process is finished, the page of the according species will be displayed. On this page the follwing information is presented:
    • Nomenclatural data (incl synonyms)
    • Description (separately Morphology and Medullary chemistry)
    • Remarks (comparison with similar taxa, remarkable diagnostic characters etc)
    • Ecology and distribution
    • Distribution map (if the species occurs in Estonia)
    • Illustrations (original coloured images)
  • Illustrations can be enlarged by clicking the picture.
  • At every step of identification and also at each species page you can go directly to other species pages and compare the taxa of interest. You can do this by clicking the corresponding epithet below the heading ‘Species in the key’.

Material and Methods

Diagnostic characters useful for the identification of European Usneas were not originally invented. Most of the morphologial characters commonly used for delimiting and identifying Usnea species such as thallus habit, branching, base, segments, fibrils, isidia/isdiomorphs, soralia, papillae etc are discussed thoroughly in several papers (Clerc 1987a, 1987b, 1998; Clerc & Herrera-Campos 1997; Halonen et al. 1998; Herrera-Campos et al. 1998; Ohmura 2001; Tõrra & Randlane 2007). Descriptions of species are based on literature cited in the species pages. Our own observations are added as well. Variation of morphology and chemistry has been studied on the materials mainly deposited in TU, but also in BILAS, H, HBG, ICEB, MAF, RJB, TALL, TAM and WI, a total of more than 2000 specimens. Samples have been collected by the authors from Estonia, Finland, Great Britain, Latvia, Lithuania, Portugal and Spain (incl Canary Islands). Photographs were taken by the second author using Nikon DS camera head DS-Fi1 under Nikon stereoscopic zoom microscope SMZ1000.

The list of European Usnea species was compiled using the taxonomic papers cited in the species pages, as well as the follwing local lichen checklists and floras:

Aptroot et al. 1999, Bielczyk 2003, Bielczyk et al. 2004, Bilovitz & Mayrhofer 2008, Ciurchea 1998, Clerc 2004, Diederich & Serusiaux 2000, Diederich et al. 2008, Fałtynowicz 1993, Fos 1998, Hafellner 2007, Hafellner & Türk 2001, Kondratyuk et al. 1998, Kondratyuk et al. 2003, Kuznetsova et al. 2007, Lisická 2005, Liška et al. 2008, Llimona & Hladun 2001, Mayrhofer et al. 2005, Mayrhofer et al. 2006, Motiejūnaitė, J. 2002b, Nimis & Martellos 2003, Pišút et al. 1996, Piterans 2001, Purvis et al. 1993, Santesson et al. 2004, Scholz 2000, Søchting et al. 2007, Suppan et al. 2000, Thell et al. 2004, Urbanavichus et al. 2008, Vĕzda & Liška 1999, Vitikainen et al. 1997.


This tool was prepared in the framework of the project KeyToNature funded under eContentplus programme. The work has been supported also by the European Union through the European Regional Development Fund (Center of Excellence FIBIR), by the Estonian Science Foundation (grant 7470) and by the Norwegian Financial Mechanisms and EEA Financial Mechanisms (grant EMP9).

We are grateful to all those fellow lichenologists who sent remarks for improving the key. Special thanks go to Teuvo Ahti and Christoph Scheidegger for useful comments and support; criticism of Philippe Clerc is acknowledged as well.