Identify the species of the lichen genus Usnea

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Usnea wasmuthii
Usnea rubicunda


Aim / Objective

  • Identify the species of the lichen genus Usnea (beard lichen) growing anywhere in Europe.


School level

Suitable for the university level; available only in English.


Identification key

The interactive tool Key to the Usnea species in Europe is available online. The key is traditionally dichotomous. The tool presents 31 species, which have been reliably reported in Europe during last 15 years. The theses/antitheses are not illustrated, but richly illustrated species pages with considerable amount of scientific information will be displayed after the identification process is finished.


On these pages the following information is presented:

1.Nomenclatural data (incl synonyms)

2.Description (separately Morphology and Medullary chemistry

3.Remarks (comparison with similar taxa, remarkable diagnostic characters etc)

4.Ecology and distribution

5.Distribution map (if the species occurs in Estonia)

6.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’. The new, improved version of the key will be uploaded during November 2008; illustrated glossary of diagnostic characters will be compiled and added to the key.


Further resources

The number of species in genus Usnea varies from 300–600 in the whole world, 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. Ca 30 lichen checklists and floras of European countries published during the last 15 years have been analysed, and the list of Usnea species, reliably recorded in Europe was compiled. The list presently includes 31 Usnea species, and probably will increase in the future. The key was on purpose built up on possibly easy characters/combinations of characters to offer identification help also to the non-specialists.


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). The full list of relevant publications is presented in the key.


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"More about lichens..." - digital lesson introducing the main terms and characters of lichens.


Preparation (Teacher set up)

1. Collect lichen thalli in nature or set this task for the students, or find suitable specimens in the herbarium of your institution.

2. Check that you are familiar with all terms used in the key. If not, use the additional literature (listed in the key) to make this clear. Decide, which terms should be explained to your students before starting the identification.

3. Put ready some of the most usual reactives (K – 10% potassium hydroxide, Pd – solution of paraphenylendiamine in alcohol) for colour tests on lichen thalli.

4. If possible, use stereomicroscopes or at least hand lens to observe the morphological characters of the specimens.

5. Reserve the computer class with online connection.


Summarising the experience

The key has been tested in the University of Tartu (Estonia) so far (November 2008), and some feedback has been received also from the lichenological community in Europe.


Statements from the students

The numerous coloured images of morphological and anatomical details are highly appreciated. The short texts to explain these details are proposed to be added.

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