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The Diversity of Lichenology: Jubilee Volume.A. Thell, M. R. D. Seaward & T. Feuerer (eds). Bibliotheca Lichenologica 100: 419–462.J. Cramer in der Gebrüder Borntraeger Verlagsbuchhandlung, Berlin · Stuttgart, 2009.

Key to European Usnea species

Tiina Randlane, Tiiu TõRRa, Andres Saag & Lauri Saag

Institute of Ecology and Earth Sciences, University of Tartu, Lai Street 38, 51005 Tartu, Estonia; e-mail: tiina.randlane@ut.ee

Abstract: A key for 32 Usnea species which have been reliably recorded in Europe is presented; short descriptions, extrapolated distribution maps and photographs of diagnostic characters are provided for each species.

Introduction

The genus Usnea Dill. ex Adans. is a large and cosmopolitan genus which includes macrolichens with an easily recognized beard-like morphology. It is among the richest genera in species within Parmeliaceae, including several hundreds of taxa. The distinction of species, however, is a very complicated task, and exact numbers are unknown for major areas of the world, even for the comparatively well-investigated Europe. About 30 lichen checklists and floras of European countries published during the last 15 years were investigated, and a list of 32 reliably recorded Usnea species was compiled; this list will certainly increase in the future. A few locally reported species which have not been seen by the authors or characterized sufficiently in the literature (e.g. U. anatolica Motyka, U. bithynica Motyka and U. czeczottiae Motyka from Bulgaria; U. decora Motyka and U. krempelhuberi Motyka from Spain; U. fascinata Bystrek from Poland, U. hookeri Motyka from Romania, U. subfaginea Nádv. from Austria), and thereby in need of further taxonomic investigation, are not included in the current study.

Our aim was to compile a practical key for identification of Usnea species in Europe. Therefore, the key was deliberately built up on the easiest characters or combinations of characters where possible, although such simplification can cause misidentifications in the case of specimens with untypical character states, which are not rare in this genus. The same key is provided in three different forms: (a) an interactive dichotomous key with numerous photogrpahs and more detailed information on the treated taxa; (b) a traditional, single-access dichotomous key with maps of extrapolated distribution patterns in Europe and photographs of diagnostic characters for each species; (c) a multi-access synoptic key; the first, interactive internet version is available at: http://www.ut.ee/ial5/k2n/key/usnea _eu/index.html) while two latter versions are presented in this paper.

A glossary of the main terms used in the keys together with brief explanations, supported by colour images, is provided.

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Material and methods

Diagnostic characters, useful for the identification of European Usnea species, were not invented by the authors. Most of the morphological characters commonly used for delimiting and identifying species, such as thallus habit, branching, base, segments, fibrils, isidia/isdiomorphs, soralia and papillae are thoroughly discussed 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 as well as on our own observations of variation in morphology and chemistry in more than 2000 specimens mainly deposited in TU, but also in BILAS, H, HBG, ICEB, MA, MACB, MAF, TALL, TAM, UPS and WI. Samples have been collected by the authors from Estonia, Finland, Great Britain, Latvia, Lithuania, Portugal, Sweden and Spain (incl. Canary Islands). Photographs were taken by the second author using a 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 descriptions, as well as the following lichen checklists and floras: a CHeCkliST of THe liCHen floRa of RuSSia (2009), apTRooT et al. (2004), BielCzyk (2003), BielCzyk et al. (2004), BiloviTz & mayRHofeR (2008), BLWG (2008), CaRvalHo (1998), CiuRCHea (1998), CleRC (2004a), diedeRiCH & SeRuSiaux (2000), diedeRiCH et al. (2008), fadeeva et al. (2007), Fałtynowicz (1993), foS (1998), HafellneR (2007), HafellneR & TüRk (2001), JameS et al. (2009), 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 (2002), nimiS & maRTelloS (2003), pišúT et al. (1996), piTeRanS (2001), SanTeSSon et al. (2004), SCHolz (2000), Seaward (2008), Sipman et al. (2005), SøCHTing et al. (2007), Suppan et al. (2000), THell et al. (2004), uRBanaviCHuS et al. (2008), Vĕzda & Liška (1999), viTikainen et al. (1997), wirth (1994, 1995a).

Distribution maps of Usnea species presented in the traditional key were composed using the listed local checklists and taxonomic papers, as well as lichen samples from herbaria mentioned above. The maps are extrapolated on a scale of individual countries, with a few exceptions, and therefore do not reveal the natural limits of species distributions. For the European part of Russia four major regions, following a CHeCkliST of THe liCHen floRa of RuSSia (2009), were recorded separately: northern, central and southern parts, and Russian part of Caucasus; furthermore, inside northern European Russia three smaller areas (Murmansk and Leningrad Regions and the Republic of Karelia), with independent checklists of lichen species, were also differentiated on the maps. The following states of presence were distinguished on the distribution maps: (a) present – indicated with dark green; (b) extinct or probably extinct – light green; (c) absent (missing in the checklist of the according country) – grey; (d) information deficient (no contemporary checklist of the country available) – white.

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Glossary

Apothecium (pl. apothecia) (Fig. 1) – a fruiting body containing asci with ascospores; in Usnea usually with marginal ray-like projections.

Base (trunk) – the basal part of the thallus, close to the attachment point.

Branch – a lateral projection of the main “stem” of the thallus. The following features of branches are diagnostically valuable (CleRC 1998): shape of branches in longitudinal section can be (a) tapering, i.e. narrowing slowly and gradually towards the end of the branch, or (b) clearly irregular; shape of branches in transverse section (Fig. 2) can be (a) terete or (b) irregular, with foveolae and ridges.

Branching – can be: (a) anisotomic-dichotomous – dividing branches are of different thickness (CleRC 1987b); (b) isotomic-dichotomous – dividing branches are more or less equal in thickness (CleRC 1987b).

Central axis (Fig. 3) – a cartilaginous strand of solid, compact, longitudinally arranged hyphae in the centre of Usnea branches. See also Thallus layers.

Cortex – outer layer of the thallus consisting of densely packed hyphae. See also Thallus layers.

Fibril (Fig. 4) – a short branch-like projection which includes a central axis similar to the usual branches, but their central axis is not attached to the axis of the branch on which they occur (CleRC & HeRReRa-CampoS 1997). Occurrence of numerous fibrils results in a “fish-bone” like appearance.

Growth habit (Fig. 5) – configuration of the thallus: (a) shrubby – thallus is more or less as wide as long, branches are generally horizontally oriented or even erect; (b) subpendent – similar to shrubby thallus but branches may be erect only at base while apices of branches are generally pendent; (c) pendent – thallus

Fig. 1. Apothecia of Usneas.

Fig. 3. Central axis.

Fig. 4. Fibrils.

Fig. 2. Shape of branches in trans-verse section. A – Terete branches. B – Irregular branches with foveolae and ridges.

A B

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is several times longer in length than in width, branches are pendent from the very base.

Isidium (pl. isidia) (Fig. 6) – vegetative propagule of lichens having spinulose habit, containing photobiont cells and being covered with cortex. Similar structures seen on the soralia of Usnea species have been termed “isidiomorphs” (CleRC 1998) because they are not considered true isidia as they are not formed as outgrowths of the cortex but are initiated from the hyphae of medulla. JameS (2003) points out that some isidia-like structures develop in soralia from soredia which may become secondarily corticated. In this paper the term “isidium” is applied to all isidia-like formations seen on Usnea-thalli. Distinguishing between true isidia and isidiomorphs needs ontogenetic studies and is probably not feasible for the users of the present key.

Medulla (Fig. 7) – the loose layer of hyphae below the cortex and algal layer; in Usnea species between the cortex and the central axis (algal layer directly below the cortex is often poorly visible); the consistency of the medulla can be: (a) compact – with agglutinated but not individually visible hyphae (CleRC 1987b); (b) dense – with agglutinated and individually visible hyphae (CleRC 1987b); (c) loose – with few separated and conspicuous hyphae (CleRC 1987b). See also Thallus layers.

Medullary substances – secondary metabolites of lichens located in the medulla are divided according to their quantity: (a) major or (b) minor, or to the constancy of their occurrence: (aa) accessory substances – substances which occur occasionally, only in some specimens of the same species; (bb) main substances – substances which occur in all or in many specimens of the same species; in the latter case different chemotypes (inside the species) are specified according to the main substances.

A B CFig. 5. Growth habit. A – Shrubby thallus. B – Subpendent thallus. C – Pendent thallus.

Fig. 6. Isidia.

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Papilla (pl. papillae) (Fig. 8) – short cylindric outgrowth of the cortex.

Pseudocyphella (pl. pseudocyphellae) (Fig. 9) – dot-like, fusiform or irregular area of the thallus where the cortex is broken and medullary hyphae reach the surface.

Segment (Fig. 10) – a part of the branch which is well demarcated by annular cracks (Halonen et al. 1999).

Soralium (pl. soralia) (Fig. 11) – collection of soredia, vegetative propagules of lichens. The following features of soralia are diagnostically valuable (CleRC 1998, HeRReRa-CampoS et al. 1998): flatness compared to the cortex of branches – (a) tuberculate soralia, (b) flat soralia, (c) concave soralia; shape – (a) rounded, (b) oblong-cylindrical, (c) transversely ellipsoid, (d) surrounding the branch bracelet-like, (c) irregular; size – (a) punctiform, (b) enlarged.

Thallus layers – see also Cortex, Medulla and Central axis. Comparison of the thickness of these three layers is an anatomical character useful for the identification of several Usnea species (CleRC 1987b). The ratio %C/%M/%A is measured, indicating the percent of the radius of the cortex and the medulla, and as a percent of the diameter of the axis.

Tubercle – a short outgrowth which is wider than papillae and with medulla inside.

A B C

Fig. 7. Medulla. A – Compact. B – Dense. C – Loose.

Fig. 8. Papillae. Fig. 9. Pseudo-cyphellae.

Fig. 10. Segments of thallus.

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Traditional dichotomous key

For the explanation of colours used on the distribution maps, see Material and methods (p. 420).

1 Thallus distinctly bicoloured, yellow, spotted with black bands, terminal parts widely blackened ........................................................ U. sphacelata

Thallus more or less uniform in colour, yellowish-green or red-orange, without black areas .................................................................................2

Fig. 11. Soralia. A, B – regularly rounded. C – oblong. D – transversely ellipsoid. E, F – bracelet-like. G, H – irregular, expanded. I – expanded, slightly tuberculate. J – isidate.

A B C D E

F G H I J

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2(1) Apothecia abundant; without any isidia or soralia ..................................3 Apothecia absent or a few, if present; isidia and/or soralia often

occur .......................................................................................................43(2) Thallus subpendent to pendent; ascospores 7.0–8.4 μm long; apothecial

disc Pd–, KC– ..................................................................... U. intermedia

Thallus shrubby; ascospores 8.5–11.0 μm long; apothecial disc Pd+ yellow, KC+ red (alectorialic acid) ............................................U. florida

4(3) Thallus pendent, may grow extremely long (up to 3 m); majority of branches almost undivided, decorticated, with numerous perpendicular fibrils ................................................................................... U. longissima

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Thallus shrubby or pendent but never longer than 60 cm; branches usually divided and always persistently corticated, with or without fibrils ..........................................................................................5

5(4) Thallus distinctly orange-red (pigment present in cortex) ....U. rubicunda

Thallus yellowish-green or grey (reddish pigments absent in cortex, however, medulla may be coloured) .......................................................6

6(5) Medulla and central axis totally or partly coloured (yellow, rose, orange, red) ..........................................................................................................7

Medulla and central axis totally white .................................................. 107(6) Outer part of the medulla white, inner part pale lemon to primrose

yellow; medulla loose ....................................................... U. flavocardia

Medulla and/or central axis differently coloured (rose, orange, red); dense to compact .....................................................................................8

8(7) Orangish or pinkish red pigment subcortical, limited to a thin medullary layer under the cortex......................................................... U. subcornuta

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Rose, orange or red pigment in ± whole medulla ....................................99(8) Medulla (and central axis) usually pink, C+ yellow; soralia at the top of

raised tubercles; contains diffractaic acid (main substance) plus barbatic and squamatic acids (accessories) ...........................................U. ceratina

Medulla wine red, C–; soralia flat or slightly tubercular; contains fatty acids (main substances) ......................................................... U. mutabilis

10(6) Thallus distinctly pendent, several times longer in length than in width .. 11 Thallus shrubby to subpendent, more or less as wide as long, main

branches erect on base and only apices may be pendent ....................... 1811(10) Older parts form clearly inflated sausage-like segments (terminal

branches less inflated) ......................................................... U. articulata

Branches do not form sausage-like segments ........................................ 1212(11) Branches even in thickness, slendering evenly towards the apices;

without foveolae and/or ridges; medulla dense or compact .................. 13

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Branches uneven in thickness, often with foveolae and/or ridges; medulla loose ........................................................................................ 17

13(12) Branches are divided into terete segments by annular cracks ± throughout the thallus ...................................................... U. chaetophora

Branches are not divided into segments or if cracked then only close to the base ................................................................................................. 14

14(13) Base clearly blackened; salazinic acid as the main medullary compound .. 15 Base greenish or brownish, but clearly not blackened; protocetraric acid

as the main medullary compound .......................................................... 1615(14) Mature soralia transversely elliptical to irregularly rounded, remaining

discrete, isidia present only on young soralia; cortex very thick, medulla very thin ................................................................................. U. silesiaca

Soralia usually remain punctiform, with abundant isidia; both cortex and medulla rather thick .............................................................. U. dasypoga

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16(14) Thallus clearly pendant; papillae always absent; cortex rather thick, matt ........................................................................... U. schadenbergiana

Thallus subpendant; papillae absent to abundant; cortex very thick, shiny .................................................................................U. subscabrosa

17(12) Branches conspicuously foveolate and ridged; fibrils absent to scarce; papillae, soralia and isidia absent .........................................U. cavernosa

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Branches slightly or distinctly foveolate and ridged; fibrils scarce to numerous; papillae absent to abundant; soralia few to abundant; isidia absent or few ............................................................................U. barbata

18(10) Papillae absent on all branches ............................................................. 19 Papillae present on main or on terminal branches or on both ................ 2219(18) Isidia always absent; medulla very loose ............................... U. glabrata

Isidia present; medulla various (loose to compact) ............................... 2020(19) Isidia numerous all along the branches; soralia punctiform; medulla

loose; contains fatty acids (main substances) and norstictic acid (accessory) ................................................................................... U. hirta

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Isidia occur only on soralia; soralia punctiform to enlarged (especially on terminal branches); medulla dense to compact; contains various depsidones, but no fatty acids ............................................................... 21

21(20) Base pale, without distinct annular cracks; contains galbinic, norstictic and salazinic acids (main substances) .......................................U. dasaea

Base pale, often with distinct annular cracks; contains stictic acid (as a main substance) and lobaric acid (accessory) .........................U. flammea

22(18) Secondary branches are distinctly constricted at their base, giving the branches an inflated appereance; medulla loose .................................... 23

Secondary branches not clearly constricted at the base, being more or less uniform in diameter; consistency of medulla various ..................... 25

23(22) Isidia absent .................................................................... U. esperantiana

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Isidia present ......................................................................................... 2424(23) Thallus clearly shrubby; soralia (and isidia) are concentrated at branch

tips, becoming confluent ..........................................................U. cornuta

Thallus shrubby to subpendent with divergent branches; soralia (containing isidia) are scattered over branches, and remain discrete .........

.......................................................................................... U. fragilescens

25(22) Isidia usually abundant ......................................................................... 26 Isidia absent or occasionally present on young soralia .......................... 3026(25) Thallus partly orange-red (always seen at the basal part of the main

stem) due to a red cortical pigment ......................................U. rubicunda

Thallus without red cortical pigment, totally yellowish-green or grey in normal conditions (however, some specimens may occasionally turn reddish, due to the decomposition of a medullary substance) ..................27

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27(26) Branches of uneven thickness, irregularly swollen, apical parts often sinuous; soralia punctiform and usually not expanding, bearing relatively tall isidia; contains salazinic acid (main substance) and accessory substances ............................................................U. diplotypus

Branches of even thickness, narrowing towards the apices, not swollen or sinuous; soralia minute to expanded, bearing relatively small isidia; contains other (besides salazinic acid) medullary substances ............... 28

28(27) Base greenish or brownish, basal part often with distinct annular cracks; contains stictic acid (main substance) .....................................U. flammea

Base black, often with transverse fissures but without annular cracks; contains other (besides stictic acid) medullary substances .................... 29

29(28) Contains norstictic acid ...................................................... U. praetervisa

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Contains squamatic or thamnolic acid.............................. U. subfloridana

30(25) Isidia occur on young soralia but are normally abraded on mature soralia ...31 Isidia totally absent ............................................................................... 3631(30) Cortex very thick (9–17%), medulla very thin (6–14%), central axis

thick (40–65%) ..................................................................................... 32 Proportions of thallus layers different (cortex mainly thinner and

medulla much thicker) .......................................................................... 3332(31) Base conspicuously blackened; fibrils present; contains salazinic acid

(main substance) .................................................................... U. silesiaca

Base pale greenish or brownish; fibrils absent or scarce; contains protocetraric acid or rarely thamnolic acid (main substance) ...U. subscabrosa

33(31) Branching mostly anisotomic-dichotomous; branches of uneven thickness, sometimes with foveolae or depressions; soralia often tuberculate ..........34

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Branching mostly isotomic-dichotomous; branches even and without foveolae; soralia often plane or slightly excavate ................................. 35

34(33) Thallus usually short, clearly shrubby; mature soralia enlarged, tuberculate to slightly excavate; soredia granulose ..............U. substerilis

Thallus shrubby to subpendent, apical parts often sinuous; mature soralia punctiform, plane to tuberculate; soredia farinose ....U. diplotypus

35(33) Soralia oblong-cylindrical; contains barbatic acid (main substance) and salazinic acid (accessory) .....................................................U. wasmuthii

Young soralia punctiform, later becoming rounded; medullary chemistry variable: contains norstictic acid (usually) or psoromic acid (rarely) as a main substance, salazinic and other substances occur as accessories ........ .......................................................................................... U. glabrescens

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36(30) Soralia (originally punctiform, later becoming larger) always remain distinctly rounded and discrete; fibrils sparse or absent .... U. glabrescens

Soralia becoming confluent and expanded; fibrils often abundant ........ 3737(36) Apical parts characteristically twisted; soralia especially crowded at the

terminal parts, remaining ± superficial ............................ U. esperantiana

Apical parts not characteristically twisted; soralia crowded or not, may become deeply concave when mature, and totally surround the terminal branches ................................................................................................ 38

38(37) Contains salazinic acid (usually) or psoromic acid (rarely) as a main substance; branches may have foveolae or depressions ....... U. lapponica

Contains norstictic acid or an unidentified compound (as a main substance); branches without foveolae and depressions ........................

.........................................................................................U. fulvoreagens

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Synoptic key

Synoptic keys have, regrettably, rarely been applied in lichenology, the most prominent example being that of elix (1993) for identifying genera in Parmeliaceae. Lists of Usnea species grouped according to their main characteristics by JameS (2003) also reveal some features of a synoptic key. The main advantages of synoptic keys include the possibilities for: (a) multi-access use – “…one starts wherever one wishes in the key, with whatever seems like a useful character” (koRf 1972), (b) progressive completion of the key – adding a new taxon or a new character to the key causes no problems, allowing such keys to be readily computerized (elix 1993) and (c) a comparatively compressed presentation of the key which in itself may serve to replace long descriptions of taxa (koRf 1972).

Usually the taxa in synoptic keys are successively numbered; the key consists of the list of characters and character states for each character, and the numbers of taxa that follow the character states which they share. For this work, short abbreviations of species epithets (listed in Table 1) were applied instead of numbering the species. In the present synoptic key, 13 characters and 51 character states have been used. Species for which only one character state of the according character is distinctive are marked in bold.

Identification of taxa using a synoptic key is as follows: (a) choose any character which is clearly distinguishable on your specimen, (b) decide which of the described character states is distinctive for your specimen, (c) write down all species abbreviations that are listed after this particular character state, (d) choose the next easily observed character, (e) select suitable character state, (f) compare the list of species abbreviations after this character state with your previous list, and cross out all the abbreviations that are not present in both lists, (g) continue choosing characters, selecting character states and comparing species lists until only one abbreviation is left uncrossed in your list, and (h) find the full name of the identified species in Table 1.

Table 1. Usnea species included in the synoptic key and their abbreviations.

Abbreviation Speciesart U. articulatabar U. barbatacav U. cavernosacer U. ceratinacha U. chaetophoracor U. cornutadasa U. dasaeadasy U. dasypogadip U. diplotypusesp U. esperantianaflam U. flammeaflav U. flavocardiaflo U. floridafra U. fragilescensful U. fulvoreagensglabra U. glabrata

Abbreviation Speciesglabre U. glabrescenshir U. hirtaint U. intermedialap U. lapponicalon U. longissimamut U. mutabilispra U. praetervisarub U. rubicundasch U. schadenbergianasil U. sileciacasph U. sphacelatasubc U. subcornutasubf U. subfloridanasubsc U. subscabrosasubst U. substeriliswas U. wasmuthii

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1. Presence of apothecia1.1. Apothecia abundant: flo, int1.2. Apothecia absent or few: art, bar, cav, cer, cha, cor, dasa, dasy, dip, esp,

flam, flav, fra, ful, glabra, glabre, hir, lap, lon, mut, pra, rub, sch, sil, sph, subc, subf, subsc, subst, was

2. Length of ascospores2.1. 7–8.4 μm: int2.2. 8.5–11 μm: flo2.3. Unknown (apothecia absent or rarely recorded): art, bar, cav, cer, cha,

cor, dasa, dasy, dip, esp, flam, flav, fra, ful, glabra, glabre, hir, lap, lon, mut, pra, rub, sch, sil, sph, subc, subf, subsc, subst, was

3. Thallus growth habit3.1. Thallus shrubby: cer, cor, dasa, dip, esp, flam, flav, flo, fra, ful, glabra,

glabre, hir, lap, mut, pra, rub, sil, sph, subc, subf, subsc, subst, was3.2. Thallus subpendent: cer, dasa, dip, flam, fra, glabre, int, mut, pra, rub,

subc, subf, sil, subsc, was3.3. Thallus pendent: art, bar, cav, cer, cha, dasy, int, lon, rub, sch, sil,

subsc4. Colour of the thallus4.1. Thallus distinctly bicoloured, yellow, spotted with black bands: sph4.2. Thallus more or less uniform in colour, orange-red: rub4.3. Thallus more or less uniform in colour, yellowish-green or grey: art, bar,

cav, cer, cha, cor, dasa, dasy, dip, esp, flo, flam, flav, fra, ful, glabra, glabre, hir, int, lap, lon, mut, pra, sch, sil, subc, subf, subsc, subst, was

5. Colour of the medulla5.1. Medulla wine red: mut5.2. Medulla pink: cer5.3. Medulla white in the inner part, orange-red under the cortex: subc5.4. Medulla white in the outer part, yellow in the inner part: fla5.5. Medulla totally white: art, bar, cav, cer, cha, cor, dasa, dasy, dip, esp,

flam, flo, fra, ful, glabra, glabre, hir, int, lap, lon, pra, rub, sch, sil, sph, subf, subsc, subst, was

6. Colour of the base6.1. Base clearly blackened: bar, cer, cha, cor, dasy, dip, flav, flo, fra, ful,

glabre, int, lap, lon, pra, sil, subf, subst, was6.2. Base concolorous to the branches or brownish, but clearly not blackened:

art, cav, cer, cha, cor, dasa, dip, esp, flam, flav, glabra, hir, int, lap, lon, mut, rub, sch, sph, subc, subsc, subst

7. Occurrence of cortex7.1. Thallus corticated throughout the whole thallus: art, bar, cav, cer, cha,

cor, dasa, dasy, dip, esp, flam, flav, flo, fra, ful, glabra, glabre, hir, int, lap, mut, pra, rub, sch, sil, sph, subc, subf, subsc, subst, was

7.2. Only base, side branches and fibrils are corticated, cortex is disintegrated on the primary branches (exposing the medulla): lon

8. Segmentation of thallus8.1. Thallus is segmented by annular cracks throughout the thallus or in its

major parts: art, cha, ful, sch, sil

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8.2. Thallus is not segmented or annular cracks only occur close to the base: bar, cav, cer, cor, dasa, dasy, dip, esp, flo, flam, flav, fra, ful, glabra, glabre, hir, int, lap, lon, mut, pra, rub, sil, sph, subc, subf, subsc, subst, was

9. Shape of branches in transverse section9.1. Terete: cer, cha, cor, dasa, dasy, dip, esp, flam, flav, flo, fra, ful, glabre,

int, lap, lon, mut, pra, rub, sch, sil, sph, subc, subf, subsc, subst, was9.2. Irregular (with foveolae and ridges): bar, cav, dip, glabra, hir, lap, sph,

subst9.3. Presence of inflated sausage-like segments (in older parts): art10. Presence of papillae10.1. Papillae occur on main or on terminal branches or on both: bar, cer, cha,

cor, dasy, dip, esp, flam, flav, flo, fra, ful, glabre, int, lap, pra, rub, sil, sph, subf, subsc, subst, was

10.2. Papillae absent on all branches: art, bar, cav, cha, dasa, flam, glabra, hir, lon, mut, sch, subc, subsc

11. Presence of isidia11.1. Isidia abundant: cor, dasa, dasy, dip, flam, hir, mut, pra, rub, subc, subsc,

subf11.2. Isidia scarce or occur on young soralia only: art, bar, cer, cha, cor, dasa,

dip, flav, fra, glabre, lon, sch, sil, subsc, subst, was11.3. Isidia absent: art, bar, cav, cer, cha, esp, flav, fra, flo, ful, glabra, glabre,

int, lap, lon, sch, sil, sph, subsc, was 12. Presence of soralia12.1. Soralia absent: art, bar, cav, cha, flo, int, lon12.2. Soralia present: bar, cer, cha, cor, dasa, dasy, dip, esp, flam, flav, fra,

ful, glabra, glabre, hir, lap, lon, mut, pra, rub, sch, sil, sph, subc, subf, subsc, subst, was

13. Occurrence of major medullary substances (species name in bold indicates that the according substance is treated as the main compound in (some chemotype of) that species; species name in regular type indicates that the according substance is accessory in the species; North or South American chemotypes are not considered)

13.1. Alectorialic acid present: dip, flo, subf13.2. Barbatic acid present: cer, dip, lap, lon, subsc, subst, was13.3. Bourgeanic acid (fatty acid) present: esp13.4. Diffractaic acid present: cer, ful, lon13.5. Fumarprotocetraric acid present: art, glabra, subsc13.6. Galbinic acid present: dasa13.7. Lobaric acid present: flam13.8. Menegazziaic acid present: flam13.9. Murolic acid (fatty acid) present: hir, mut13.10. Norstictic acid present: cor, dasa, flam, ful, glabra, glabre, hir, pra, rub,

subc13.11. Protoceraric acid present: art, bar, cor, dasy, dip, ful, glabra, glabre, lap,

sch, subsc, subst, was13.12. Psoromic acid present: flav, glabre, lap, rub, was

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13.13. Salazinic acid present: bar, cav, cha, cor, dasa, dasy, dip, esp, flav, ful, glabra, glabre, int, lap, rub, sil, subst, was

13.14. Squamatic acid present: cer, flo, ful, subf, was (?)13.15. Stictic acid present: cor, esp, flam, fra, ful, glabre, rub, subc13.16. Thamnolic acid present: flo, subf, was13.17. Unidentified fatty acid (neither bourgeanic nor murolic acid) present:

flav13.18. Unidentified substance (characteristics of the substance see in the

description of U. fulvoreagens) present: ful13.19. Medullary compounds absent: bar, cav, cha, dasy, ful, glabra, glabre, hir,

lap, sph, subst, was

The species

Usnea articulata (L.) Hoffm.Deutschl. Fl. 2: 133 (1796).—Lichen articulatus L., Spec. Plant. 2: 1156 (1753).

Morphology. For a detailed description, see SwinScow & krog (1976) and (JameS et al. 2009). Easily identified by the pendulous thallus with inflated (up to 3 mm) sausage-like segments which are conspicuous at the older part of the thallus; base concolorous to the branches or light brown; fibrils scarce or absent; papillae absent; isidia present or absent; soralia absent but soredia-like propagules may be produced by pseudocyphellae; pseudocyphellae usually present, punctiform, sometimes enlarged. Cortex thin; medulla thin and extremely loose.

Medullary chemistry. Five chemotypes have been identified in East Africa (SwinScow & krog 1976), one of which is known in Europe – with fumarprotocetraric acid as a main and protocetraric acid as an accessory substance.

Ecology & distribution. The species is generally distributed in Europe in its western, central and southern areas where it grows on branches of deciduous or coniferous trees but may also scramble over low scrub vegetation in coastal sites (JameS 2003); very sensitive to SO2 air pollution (JameS et al. 2009). Reported in Europe: Albania, Belgium (probably extinct), Czech Republic (probably extinct), France (probably extinct), Germany, Great Britain, Greece, Hungary, Ireland, Italy, Netherlands, Poland, Portugal, Romania, Russia (Caucasus, Republic of Adygeja), Slovakia (probably extinct), Slovenia, Spain, Switzerland (probable) and Ukraine.

Usnea barbata (L.) F.H. Wigg.Brit. Fl. 1: 206 (1780); emend. Jørgensen et al., Bot. J. Linn. Soc. 115: 280 (1994).—Usnea alpina Motyka, Lich. Gen. Usnea Stud. Monogr., Pars Syst. 1: 214 (1936).—Usnea caucasica Vain., Természetr Füzetek 22: 275 (1899).—Usnea cembricola Motyka, Lich. Gen. Usnea Stud. Monogr. Pars. Syst. 1: 152 (1936).—Usnea freyi Motyka, Lich. Gen. Usnea Stud. Monogr. Pars. Syst. 1: 213 (1936).—Usnea implexa (Lam.) Motyka, Lich. Gen. Usnea Stud. Monogr., Pars Syst. 1: 142 (1936).—Usnea maxima Motyka, Lich. Gen. Usnea Stud. Monogr., Pars Syst. 1: 154 (1936).—Usnea pendulina Motyka, Lich. Gen. Usnea Stud. Monogr., Pars Syst. 1: 136 (1936).—Usnea plicata (L.) Weber ex F. H.Wigg.—Usnea prostrata Vain. ex Räsänen, Medd. Soc. Fauna Fl. Fenn. 46: 160 (1921).—Usnea rugulosa Vain.—Usnea scabrata Nyl., Flora 58: 103 (1875).—Usnea

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scrobiculata Motyka, Lich. Gen. Usnea Stud. Monogr., Pars Syst. 1: 144 (1936).—Usnea silvatica Motyka, Lich. Gen. Usnea Stud. Monogr., Pars Syst. 1: 151 (1936).—Usnea tenax Motyka, Lich. Gen. Usnea Stud. Monogr., Pars Syst. 1: 157 (1936).—Usnea tortuosa De Not., Giorn. Bot. Ital. 2, 1(1): 202 (1846).

Morphology. For a detailed description, see Halonen et al. (1998), HeRReRa-CampoS et al. (1998), and CleRC (2007). The species is very polymorphic and may represent a collection of intergrading taxa; several characters (e.g. presence of fibrils, papillae and isidia; degree of depressions and ridges) vary greatly. Thallus pendulous, may be partly divided into irregular segments by annular cracks; branches uneven in thickness, often with depressions and/or ridges; base blackened; fibrils few to numerous; isidia few or absent [abundant in North America according to BRodo et al. (2001)]; papillae abundant, sparse or absent; soralia punctiform and irregular, few to abundant, develop on the top of eroded papillae, tubercles or ridges. Cortex thin; medulla thick and loose.

Medullary chemistry. Two chemotypes have been recorded: (1) with salazinic acid as a main substance (K+ yellow, orange or red, Pd+ yellow to orange) and protocetraric acid as an accessory substance; (2) without medullary substances (K–, Pd–) (Halonen et al. 1998).

Notes. Some specimens which have numerous fibrils may be confused with U. dasypoga; consistency of medulla should be checked then (loose medulla in U. barbata, and dense in U. dasypoga).

Ecology & distribution. Corticolous. Reported in Europe: Austria, Bulgaria, Czech Republic, Denmark, Estonia, Finland, Germany, Greece, Italy, Latvia, Lithuania, Norway, Poland, Romania, Russia (northern part, Caucasus), Slovakia, Slovenia, Spain, Sweden, Switzerland and Ukraine.

Usnea cavernosa Tuck.in Agassiz, Lake Superior, p. 171 (1850).

Morphology. For a detailed description, see Halonen et al. (1998), HeRReRa-CampoS et al. (1998) and CleRC (2007). Thallus pendulous, with parallel branches; base pale; branches uneven in thickness, conspicuously foveolate and ridged, annular cracks may be numerous but generally are inconspicuous; fibrils absent to scarce; papillae absent; soralia and isidia absent. Cortex thin, shiny; medulla loose to dense, thick; central axis often sinuous.

Medullary chemistry. Chemotype (1) with salazinic acid as a main substance (K+ red, Pd+ yellow to orange) is known from Europe, North America and Asia; chemotype (2) with no medullary compounds (K–, Pd–) is reported as very rare in British Columbia (Halonen et al. 1998).

Notes. Pendulous thallus with parallel foveolate branches, and absence of papillae, soralia and isidia are the diagnostic characters of this easily distinguished species.

Ecology & distribution. Corticolous, mainly on conifers (wirth 1995a, b; Halonen et al. 1998). Distributed in Europe, mainly in central and southern areas. Reported in Europe: Austria, Bulgaria, Germany, Italy, Poland, Romania, Russia (central part, Caucasus), Slovakia (probably extinct), Slovenia, Switzerland and Ukraine.

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Usnea ceratina Ach.Lichenogr. Univ.: 619 (1810).

Morphology. For a detailed description, see Halonen et al. (1998), HeRReRa-CampoS et al. (1998) and CleRC (2007). Thallus shrubby to pendulous, coarse and tough; base concolorous to the branches or grey; fibrils and papillae sparse to numerous; tubercles conspicuous and numerous on larger branches, becoming white at the top and bearing soralia and/or isidia. Cortex thick and glossy; medulla thick and dense, light pink to pink, occasionally white; central axis pink to almost red, rarely white.

Medullary chemistry. Diffractaic acid (K–, Pd–, C+ pale yellow, CK+ yellow to yellow-orange) is present as a main substance, barbatic and squamatic acids as accessory substances; amount of unidentified pink and/or yellow pigments varies.

Notes. Distinguished by the coarse-texured thallus and unique chemistry (presence of diffractaic acid); pink medulla and axis are of help in determination of juvenile specimens (JameS 2003).

Ecology & distribution. Corticolous, on old trees with a rather acid bark in well-lit situations (diedeRiCH et al. 2008, JameS et al. 2009). The species is widely distributed both in the Northern and Southern hemispheres; reported in Europe: Austria, Belgium, Bulgaria, Czech Republic (probably extinct), France, Germany, Great Britain, Hungary, Italy, Ireland, Latvia, Luxembourg (probably extinct), Netherlands (probably extinct), Poland, Portugal, Romania, Russia (Caucasus), Slovakia (probably extinct), Slovenia, Spain, Sweden (one locality in southern part, probably extinct), Switzerland and Ukraine.

Usnea chaetophora Stirt.Scott. Naturalist Nov. Ser. 1: 76 (1883).—Usnea leiopoga Motyka, Lich. Gen. Usnea Stud. Monogr. Pars. Syst. 1: 187 (1936).

Morphology. For a detailed description, see Halonen et al. (1998). Thallus pendulous, with numerous and smooth branches; most branches are divided by annular cracks into regular segments up to almost terminal parts; fibrils, isidia, papillae and tubercles absent or scarce; soralia few, punctiform. Cortex rather thick; medulla thin and dense.

Medullary chemistry. Two chemotypes have been reported by Halonen et al. (1998) from British Columbia, Canada: (1) with salazinic acid as a main substance (K+ yellow, orange or red, Pd+ yellow to orange) is more usual; (2) without medullary substances (K–, Pd–) occurs occasionally. Both are known also from Europe (TõRRa & Randlane 2007).

Notes. Pendulous thallus, absence (or scarce presence) of fibrils and isidia, and annulation of branches throughout the thallus (not only at the base) are the diagnostic characters. Sometimes may resemble U. barbata and then consistency of medulla should be checked (dense medulla in U. chaetophora, and loose in U. barbata).

Ecology & distribution. Corticolous. Bulgaria, Estonia, Germany, Great Britain (Scotland), Norway, Poland, Russia (Caucasus), Slovakia, Spain, Sweden and Ukraine.

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Usnea cornuta Körb.Parerga lichenologica, p. 2, Breslau (1865).—Usnea confusa Asahina, Lich. Jap. 3: 97 (1956).—Usnea inflata Delise ex Duby, Botanicon Gallicum 2: 615 (1830), nom. nud.—Usnea inflata (Duby) Motyka, Lich. Gen. Usnea Stud. Monogr., Pars Syst. 2(1): 510 (1937).—Usnea intexta Stirt.

Morphology. For a detailed description, see CleRC (1987b, 2007) and JameS et al. (2009). Thallus clearly shrubby, 2–6(–10) cm; main branches inflated, secondary branches distinctly constricted at their base, secondary branches often curved; base concolorous to the branches or light brown; fibrils present, often numerous on the tips; papillae few to numerous; soralia (and isidia) are concentrated at branch tips (including fibrils), becoming confluent, while young soralia are punctiform; isidia are numerous at the beginning, but often eroded on old soralia. Cortex glossy, thin; medulla thick and loose.

Medullary chemistry. Two chemotypes have been recorded by CleRC (1987b) and JameS et al. (2009) from Europe: (1) with salazinic acid as a main substance (K+ red, Pd+ yellow to orange) and protocetraric acid as an accessory and (2) with stictic and norstictic acids as main substances (K+ yellow to orange, Pd+ yellow to orange) and salacinic acid as an accessory. Further chemotypes are reported from North America, Sonoran region by CleRC (2007): (3) with lobaric and norstictic acids as main substances, (4) with norstictic acid alone as a main substance, (5) with protocetraric acid alone as a main substance and (6) with no medullary compounds. Various substances (e.g. consalazinic, constictic, cryptostictic, menegazziaic acids or fatty acids) may additionally occur as minor accessories in different chemotypes.

Notes. Belongs to the U. fragilescens aggregate. Morphologically a highly variable taxon.

Ecology & distribution. Mainly corticolous (81%), but may also grow on rocks (19%) (CleRC 1987b). Reported in Europe: Belgium, Bulgaria, Czech Republic (probably extinct), France (probably extinct), Germany, Great Britain, Greece, Ireland, Italy, Luxembourg (probably extinct), Netherlands, Norway (southern part only), Poland, Portugal, Romania, Switzerland and Spain.

Usnea dasaea Stirt.Scott. Naturalist 6: 106 (1881).—Usnea dolosa Motyka, Lich. Gen. Usnea Stud. Monogr., Pars Syst. 2(1): 494 (1937).—Usnea galbinifera Asahina, J. Jap. Bot. 38: 257 (1963).—Usnea spinigera Asahina, Lich. Jap. 3: 85 (1956).—Usnea spinulifera (Vain.) Motyka, Lich. Gen. Usnea Stud. Monogr., Pars Syst. 2(1): 518 (1937).—Usnea undulata Stirt., Scott. Naturalist 6: 104 (1881).

Morphology. For a detailed description, see CleRC & HeRReRa-CampoS (1997) and CleRC (2007). Thallus shrubby to subpendent, 2–15 cm; base greenish or pale brownish, without distinct annular cracks; secondary branches slightly to distinctly constricted at their point of attachment; fibrils present, occasionally numerous, spinulous; papillae absent on all branches; soralia punctiform to slightly elliptic longitudinally (especially on terminal branches), with isidia. Cortex glossy, thin; medulla thick, dense to compact.

Medullary chemistry. Galbinic, norstictic and salazinic acids are present as main substances (K+ red, Pd+ orange).

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Notes. Belongs to the U. fragilescens aggregate. Presence of numerous fibrils, while papillae are totally absent are characters to distinguish this taxon from other shrubby species. May be confused with U. hirta, which has numerous isidia all over the thallus, and a different chemistry.

Ecology & distribution. Mainly corticolous, but may also grow on rocks (CleRC & HeRReRa-CampoS 1997). Worldwide (CleRC 2007); distribution in Europe is southwestern (foS & CleRC 2000). Reported in Europe: France, Italy (?), Portugal, Romania, Slovenia and Spain.

Usnea dasypoga (Ach.) Nyl.(1875), according to Halonen & Ahti, in litt.—Usnea capillaris Motyka, Lich. Gen. Usnea Stud. Monogr., Pars Syst. 1: 185 (1936).—Usnea esthonica Räsänen, Ann. Acad. Sci. Fenn., Ser. A4, 34(4): 18–19 (1931).—Usnea filipendula Stirt., Scott. Naturalist 6: 104 (1881).—Usnea flagellata Motyka, Lich. Gen. Usnea Stud. Monogr., Pars Syst. 1: 204 (1936).—Usnea hirtella (Arnold) Motyka, Lich. Gen. Usnea Stud. Monogr., Pars Syst. 1: 220 (1936).—Usnea muricata Motyka, Lich. Gen. Usnea Stud. Monogr., Pars Syst. 1: 219 (1936).—Usnea sublaxa Vain.

Morphology. For a detailed description, see Halonen et al. (1998) and HeRReRa-CampoS et al. (1998). Variable taxon. Thallus pendulous; base blackened; branches gradually tapering; fibrils and isidia conspicuous and numerous; papillae and tubercles sparse to abundant, mostly on main branches; soralia punctiform, rarely enlarging, often bearing isidia. Cortex thick; medulla rather thick, dense.

Medullary chemistry. (1) chemotype with salazinic acid as a main substance (K+ yellow, orange or red, Pd+ yellow to orange) and protocetraric acid as an accessory substance is known from Europe and North America; (2) chemotype without medullary substances (K–, Pd–) has been reported from Europe (Halonen et al. 1998).

Notes. Distinction from U. barbata see under that species.Ecology & distribution. Corticolous. Reported in Europe: Austria, Belgium,

Bulgaria, Czech Republic, Denmark, Estonia, Finland, France, Germany, Great Britain, Hungary, Ireland, Italy, Latvia, Lithuania, Luxembourg, Netherlands (probably extinct), Norway, Poland, Romania, Russia (northern and central parts, Caucasus), Slovakia, Slovenia, Spain, Sweden, Switzerland and Ukraine.

Usnea diplotypus Vain.Medd. Soc. Fauna Fl. Fenn. 48: 172 (1925).

Morphology. For a detailed description, see Halonen et al. (1998, 1999). Thallus shrubby, often subpendent; base concolorous to the branches to distinctly blackened; branching mainly anisotomic-dichotomous; branches of uneven thickness, may be irregularly swollen and have depressions, branch tips often twisted; fibrils and papillae present but their number is variable; isidia frequently numerous and relatively long; soralia punctiform and usually not expanding, soredia farinose. Cortex thin; medulla variable both in density and thickness.

Medullary chemistry. Salazinic acid (K+ yellow, orange or red, Pd+ yellow to orange) is present as a main substance, and protocetraric, barbatic, 4-O-demethylbarbatic and alectorialic acids occur as accessories in Europe and North America (CleRC 1987b; Halonen et al. 1998; TõRRa & Randlane 2007).

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Notes. Close to U. lapponica and U. substerilis: all these taxa have a more or less shrubby thallus, anisotomic-dichotomous branching, and branches of uneven thickness, with occasional foveolae and depressions. U. diplotypus often has a subpendent thallus, twisted branch tips and comparatively long isidia, while on U. substerilis short isidia are present only on young soralia, and on U. lapponica they are totally absent. All three species have similar chemotypes (with salazinic acid as a main substance) and therefore identification of medullary compounds is no help for distinguishing these taxa.

Ecology & distribution. Corticolous. Reported in Europe: Austria, Bulgaria, Czech Republic, Estonia, Finland, Germany, Hungary, Italy, Lithuania, Norway, Poland, Russia (northern, central and southern parts), Slovenia, Spain, Sweden and Switzerland.

Usnea esperantiana P. ClercCandollea 47: 2 (1992).

Morphology. For a detailed description, see CleRC (1992, 2007) and JameS et al. (2009). Thallus clearly shrubby, erect, 4–6 cm; secondary branches distinctly constricted at their base; base pale to light brownish, never blackened; fibrils present, short and numerous over the whole thallus, terminal branches often twisted, resembling octopus arms; papillae small, scarce; soralia numerous, small or usually large and rounded to irregularly shaped but always without isidia. Medulla loose.

Medullary chemistry. Contains salazinic (K+ red, Pd+ orange) acid and stictic acid complex together with bourgeanic acid (a fatty acid).

Notes. Belongs to the U. fragilescens aggregate. Constriction of branches at their base and absence of isidia on numerous flat soralia are the diagnostic morphological characters; presence of bourgeanic acid is a unique chemical character, but its identification is only possible using TLC.

Ecology & distribution. Corticolous on a large variety of trees and bushes, especially on twigs and thin branches. It has a distinct south European-Atlantic distribution (foS & CleRC 2000). Reported in Europe: Great Britain, France, Greece, Ireland, Italy, Netherlands, Portugal, Russia (Caucasus) and Spain.

Usnea flammea Stirt.Scott. Naturalist 6: 104 (1881).—Usnea dalmatica Motyka, Lich. Gen. Usnea Stud. Monogr., Pars Syst. 1: 263 (1936).—Usnea rupestris Motyka, Lich. Gen. Usnea Stud. Monogr., Pars Syst. 2(1): 323 (1937).

Morphology. For a detailed description, see CleRC (1987b) and JameS et al. (2009). Thallus shrubby, erect to subpendent, 3–8 cm; base pale, basal part often with distinct annular cracks; branches of even thickness, narrowing towards the apices, not swollen or inflated; fibrils present; papillae absent (especially in the basal area) or few, verrucous when present; soralia usually large, densely covered with isidia. Thickness and shining of the cortex varies; medulla dense to compact.

Medullary chemistry. Contains stictic acid as a main substance (K+ yellow to red, Pd+ orange) and lobaric, menegazziaic and norstictic acids as accessories. Lobaric acid is present in c. 80% of the specimens tested; it can be used as a diagnostic character for this taxon as lobaric acid has not been recorded in any other European Usnea (CleRC & may 2007).

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Notes. Belongs to the U. fragilescens aggregate. Occurrence of distinct white annular cracks in the basal part helps to recognize the species. Both cortex and inner structures (axis and medulla adjacent to the axis) may sometimes become orange due to decomposition of a medullary substance.

Ecology & distribution. Mainly corticolous (67%), may grow on mossy trees, shrubs, Calluna stems, decorticated wood etc., but also on rocks (33%) (CleRC 1987b). Its distribution is considered euoceanic, extending from the south-western coast of Norway and the British Isles to the Mediterranian region (foS & CleRC 2000). Reported in Europe: Croatia, France, Greece, Great Britain, Ireland, Italy, Luxembourg (probably extinct), Norway (southern part only), Portugal and Spain.

Usnea flavocardia RäsänenRevista Universitaria (Santiago) 21: 139 (1936).—Usnea quercina Bystrek & Gorzynska, Ann. Univ. Mariae Curie Sklodowska, Sect. 3, Biol. 17: 184 (1985).—Usnea wirthii P. Clerc, Saussurea 15: 33–36 (1984).

Morphology. For a detailed description, see CleRC (1984b, 2007) and JameS et al. (2009). Thallus shrubby, erect, to 5 cm long; base greenish or brownish to almost black; branches rather stout, may be constricted at the base, distinctly segmented by conspicuous annular cracks (bordered with white rings of medullary tissue on the main branches); fibrils sparse or numerous; papillae present, low, inconspicuous; soralia numerous, especially towards the apical parts of the thallus, convex, plane or slightly excavate, soredia rather coarse; isidia few (on young soralia) or absent (on mature soralia). Cortex thin, often covered by scattered red spots; medulla thick, loose (around the axis) and more compact close to the cortex; inner part of medulla and axis are pale lemon to primrose yellow, while outer part of medulla is white.

Medullary chemistry. Chemotype (1) with psoromic acid (K+ yellow, Pd+ yellow) as a main substance and salazinic acid and unidentified fatty acid as accessories is known from Europe; chemotype (2) with norstictic and stictic acids (K+ yellow to red, Pd+ orange) is reported from North America (Halonen et al. 1998); chemotype (3) with salazinic (K+ yellow to red, Pd+ orange), norstictic and galbinic acids as main substances was detected in the type material from Chile (CleRC 2004b); chemotype (4) without medullary substances (K–, Pd–) has been reported from Sonora, North America (CleRC 2007).

Psoromic acid in chemotype (1) is concentrated in soralia, therefore the colour test with Pd should be done on soralia rather than on medulla.

Ecology & distribution. Corticolous on deciduous trees (e.g. Fagus, Quercus, Salix and Sorbus), rarely on mossy boulders (CleRC 2004b, JameS et al. 2009). Reported in Europe: France, Great Britain, Greece, Ireland, Netherlands, Portugal and Spain.

Usnea florida (L.) F. H. WiggPrim. Fl. Holsat. 2: 7 (1780).—Lichen floridus L., Spec. Plant. 2: 1156 (1753).—Usnea tominii Räsänen in Tomin, Trudy Tyflissk. Bot. Inst. 1: 371 (1933).

Morphology. For a detailed description, see CleRC (1984a) and JameS et al. (2009). Thallus shrubby; base blackened; fibrils numerous, becoming curved at the tips; isidia absent, papillae abundant, low, mostly on main branches; soralia

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absent; apothecia frequent, arising at apices of primary and secondary branches, with long (up to 5 mm) marginal projections. Ascospores 8.5–11 μm. Cortex rather thick; medulla thin, dense.

Medullary chemistry. Two chemotypes are known in Europe: (1) with thamnolic acid as a major substance (K+ yellow, Pd+ orange) and alectorialic acid as an accessory substance (in apothecia, K+ yellow, Pd+ yellow, KC+ red on disc); (2) with squamatic acid (K–, Pd–) (CleRC 1984a; aRTiCuS et al. 2002). Chemotype (1) is more widely recorded (CleRC 1984a). CleRC (2007) reported chemotype (3) with salazinic acid as a major substance and norstictic acid as an accessory from Sonora, North America, but is unsure whether this chemotype can be accepted as U. florida s.str.

Notes. The species is typically richly fertile and always lacking any vegatative propagules (soralia or isidia). Specimens with both soralia/isidia and apothecia (usually with only a few apothecia) are assigned to U. subfloridana (JameS 2003).

This species differs from another fertile European taxon, U. intermedia, by its shrubby thallus and longer ascospores (7.0–8.4 μm long in U. intermedia). Positive Pd and KC colour tests on the apothecial disc are useful for the identification of U. florida specimens belonging to the more widely distributed chemotype (1), with thamnolic and alectorialic acids.

U. florida is considered to be the primary, fertile counterpart in a species pair where U. subfloridana is the sterile, secondary counterpart (CleRC 1984a), but phylogenetic analyses have demonstrated that the specimens of these two taxa do not form two monophyletic clades according to the method of reproduction, but fall into one intermixed group (aRTiCuS et al. 2002).

Ecology & distribution. Corticolous, preferring to grow on old deciduous trees in areas with high atmospheric humidity, but also reported from conifers (e.g. Abies and Picea) (CleRC 1984). A serious decline is recorded or suspected due to rising levels of eutrophication (JameS 2003). Recorded in Europe: Albania, Austria, Belgium, Bosnia, Bulgaria, Czech Republic, Denmark (probably extinct), France, Germany, Great Britain, Hungary, Italy, Latvia, Lithuania, Luxembourg, Netherlands (probably extinct), Norway, Poland, Portugal, Romania, Russia (northern and central parts, Caucasus), Slovakia, Slovenia, Spain, Sweden (southern part only), Switzerland and Ukraine.

Usnea fragilescens Hav. ex LyngeSkr. Vidensk.-Selsk. Christiana, Math.-Naturvidensk. Kl. 7: 230 (1921).

Morphology. For a detailed description, see CleRC (1987b, 2007) and JameS et al. (2009). Thallus shrubby to subpendent, with divergent branches, 3–5(–12) cm; base black; main branches elongate, somewhat inflated, secondary branches distinctly constricted at their base; fibrils few or numerous, rather long; papillae numerous; soralia scattered over branches, punctiform at first, and large when mature but remaining discrete; isidia few, usually seen on the tips of branches and absent on mature soralia. Cortex glossy, thin; medulla thick and loose.

Medullary chemistry. Chemotype (1) with stictic acid complex (K+ yellow to red, Pd+ orange) is known in Europe (CleRC (1987b); further chemical variability is reported from Sonora, North America (CleRC 2007): chemotype (2) with psoromic acid as a major substance (K+ yellow, Pd+ yellow); chemotype (3) with salazinic acid as a major substance (K+ yellow to red, Pd+ orange).

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Notes. Most of saxicolous specimens belong to var. fragilescens, while corticolous specimens are treated as var. mollis (Vain.) P. Clerc (CleRC (1987b), which is shorter, more tufted and more isidiate.

Ecology & distribution. Grows on rocks and boulders as well as on trees, mainly on broad-leaved (JameS et al. 2009). Reported in Europe: Belgium, France, Germany, Great Britain, Ireland, Italy, Netherlands (probably extinct), Norway (southern part only), Poland, Russia (central part and Caucasus) and Spain.

Usnea fulvoreagens (Räsänen) RäsänenLich. Fenn. Exs. no 13 (1935).—U. glabrescens (Nyl. ex Vain.) Vain. var. fulvoreagens Räsänen, Ann. Acad. Sci. Fenn. Ser. A4, 34(4): 20 (1931).

Morphology. For a detailed description, see Halonen et al. (1999) and CleRC (2007). Thallus shrubby, usually richly branched, mainly isotomic-dichotomous, branches gradually tapering; base distinctly blackened; annular cracks often abundant and with thick white medullary rings; fibrils numerous; isidia always absent; papillae abundant on main branches; soralia excavate when mature and may totally surround the terminal branches. Cortex thick; medulla rather thin, loose to dense.

Medullary chemistry. Chemically very variable but the presence of norstictic acid can be used as a diagnostic character in many cases. Treatment of chemotypes also varies by different authors (JameS et al. 2009; Halonen et al. 1999; foS & CleRC 2000). The following chemotypes are accepted here: (1) chemotype with norstictic acid (K+ red, Pd+ orange) as a main substance and different accessory substances (stictic acid complex, protocetraric and diffractaic acids) is the commonest in Europe (JameS et al. 2009; Halonen et al. 1999); (2) chemotype with salazinic and norstictic acids (K+ red, Pd+ yellow to orange) plus accessory substances reported from Fennoscandia (Halonen et al. 1999); (3) chemotype with norstictic and squamatic acids as main compounds reported from Spain (foS & CleRC 2000). Two further chemotypes are reported by TõRRa & Randlane (2007): (4) with an unknown substance (Rf class 2 in A, dark fingerprint-like spot in UV 254, blue in UV 366, dark yellow after treatment with H2SO4, dark blue in UV 366 after acid and heating, not belonging to the stictic acid complex) as a main substance (K–, Pd–); (5) without medullary substances (K–, Pd–).

Notes. Close to U. glabrescens and U. wasmuthii: they all have shrubby thalli, isotomic-dichotomous branching, and branches without foveolae or depressions. U. fulvoreagens always lacks isidia and is often characterized by bracelet-like soralia which may totally surround terminal branches, becoming excavate when mature. Both U. glabrescens and U. wasmuthii may have isidia on young soralia, while their soralia are somewhat different in the shape; U. glabrescens has young punctiform soralia, later becoming regularly rounded but still staying discrete, but U. wasmuthii has typically oblong-cylindrical soralia.

Ecology & distribution. Corticolous. Recorded in Europe: Austria, Belgium, Bulgaria, Czech Republic, Estonia, Finland, Germany, Great Britain (Scotland), Hungary, Ireland, Italy, Latvia, Lithuania, Luxembourg, Netherlands, Norway, Poland, Portugal, Romania, Russia (northern and central parts, Caucasus), Slovakia (probably extinct), Slovenia, Spain, Sweden, Switzerland and Ukraine.

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Usnea glabrata (Ach.) Vain.Ann. Acad. Sci. Fenn., Ser. A4, 6(7): 7 (1915).—Usnea plicata (L.) F.H. Wigg. var. glabrata Ach., Lichenogr. Univ.: 624 (1810).—Usnea sorediifera (Arnold) Lynge, Skr. Vidensk.-Selsk. Christiana, Math.-Naturvidensk. Kl. 7: 229 (1921).

Morphology. For a detailed description, see myllyS (1994), Halonen et al. (1998, 1999) and CleRC (2007). Thallus shrubby, small (not exceeding 5 cm, often less); branches somewhat inflated, foveolate and constricted at ramification points; base of the same colour as the rest of the thallus; fibrils numerous; isidia absent; papillae usually absent; conspicuous soralia mostly near the apices of branches and fibrils, large and may become confluent. Cortex thin, shiny; medulla thick, very loose; central axis thin.

Medullary chemistry. (1) chemotype with protocetraric and fumarprotocetraric acids as main compounds (K± brownish, Pd+ red) and several substances as accessories is known in Europe and North America; (2) chemotype with salazinic and norstictic acids as main substances (K+ red, Pd+ yellow to orange) and with different accessory compounds has been reported from Fennoscandia (Halonen et al. 1999); (3) acid deficient chemotype without medullary substances (K–, Pd–) occurs both in Europe and North America (CleRC 1987b, myllyS 1994, BRodo et al. 2001).

Notes. Easily recognized by morphological characters (small shrubby thallus, constriction of secondary branches at their base, presence of rather large soralia, and absence of both papillae and isidia). Medullary chemistry is of great help in case of chemotype (1), as fumarprotocetraric and protocetraric acids do not occur as main compounds in other shrubby species.

Ecology & distribution. Corticolous. Reported in Europe: Austria, Belgium, Bulgaria, Czech Republic (probably extinct), Denmark, Estonia (probably extinct), Finland, Germany, Great Britain, Hungary, Italy, Lithuania (probably extinct), Netherlands (probably extinxt), Norway, Poland, Portugal, Romania, Russia (northern and central parts, Caucasus), Slovakia (probably extinct), Slovenia, Spain, Sweden, Switzerland and Ukraine.

Usnea glabrescens (Nyl. ex Vain.) Vain.Medd. Soc. Fauna Fl. Fenn. 48: 173 (1925).—Usnea barbata (L.) F. H. Wigg. var. glabrescens Nyl. ex Vain., Meddel. Soc. Fauna Fl. Fenn. 2: 46 (1878).—Usnea betulina Motyka, Lich. Gen. Usnea Stud. Monogr., Pars Syst. 1: 297 (1936).—Usnea compacta Motyka, Lich. Gen. Usnea Stud. Monogr., Pars Syst. 1: 294 (1936).—Usnea distincta Motyka, Lich. Gen. Usnea Stud. Monogr., Pars Syst. 1: 298 (1936), nom. illeg.—U. extensa Vain., Ann. Acad. Sci. Fenn., Ser. A4, 27(6): 68 (1928).

Morphology. For a detailed description, see Halonen et al. (1998, 1999). Thallus originally shrubby, later may become subpendent; branching mainly isotomic-dichotomous; base distinctly blackened, often with transverse annular cracks; fibrils present at basal parts and sparse to absent at apical parts; isidia rarely present only on young soralia; papillae present on main branches and absent on secondary branches; young soralia punctiform, later becoming larger but usually staying distinctly rounded and discrete. Cortex rather thick; medulla variable.

Medullary chemistry. Chemistry is variable, with several chemotypes reported: (1) chemotype with norstictic and salazinic acids (K+ red, Pd+ yellow to orange) as main compounds, plus other compounds of the stictic acid complex

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and protocetraric acid as accessory substances is the commonest in Fennoscandia; (2) with norstictic acid as main substance (K+ red, Pd+ orange) plus stictic acid complex as accessories is widely known in Fennoscandia (Halonen et al. 1999) and Great Britain (JameS 2003); (3) chemotype with psoromic acid (K–, Pd+ yellow) and accessory substances is rare in Great Britain (CleRC 1992; JameS 2003); (4) chemotype without medullary substances (K–, Pd–) has been reported as rare in east Fennoscandia (Halonen et al. 1999).

Notes. For diferences from closely related taxa, see under U. fulvoreagens.Ecology & distribution. Corticolous. Reported in Europe: Austria, Bulgaria,

Czech Republic, Denmark, Estonia, Finland, Germany, Great Britain, Greece, Hungary, Ireland, Italy, Latvia, Lithuania, Norway, Poland, Portugal, Romania, Russia (northern and central parts, Caucasus), Slovakia, Slovenia, Spain, Sweden, Switzerland and Ukraine.

Usnea hirta (L.) F.H. Wigg.Prim. Fl. Hols.: 91 (1780).—Lichen hirtus L., Spec. Plant. 2: 1155 (1753).—Usnea foveata Vain.—Usnea glaucescens Vain., Meddel. Soc. Fauna Fl. Fenn. 48: 172 (1925).—Usnea pulvinata Räsänen, Ann. Acad. Sci. Fenn. Ser. A 34(4): 20 (1931), nom. illeg.—Usnea romanica Cretzoiu—Usnea variolosa Motyka, Lich. Gen. Usnea Stud. Monogr., Pars Syst. 1: 104 (1936).

Morphology. For a detailed description, see Halonen & puolaSmaa (1995) and Halonen et al. (1998). Thallus shrubby, richly branched; branching mainly anisotomic-dichotomous; main branches slightly deformed and foveolate, also constrictions may occur; base pale greenish or brownish; fibrils often abundant; isidia numerous, scattered or in clusters, more abundant at the terminal parts; papillae absent; soralia punctiform and develop on the scars where isidia have broken off. Cortex thin; medulla thick and usually loose.

Medullary chemistry. (1) chemotype with fatty acids (of the murolic acid complex) (K–, Pd–) is widely distributed both in Europe and North America, with the presence of norstictic acid (K+ red, Pd+ orange) as an accessory substance reported in Eastern Fennoscandia (Halonen & puolaSmaa 1995); (2) chemotype without any medullary substances is known from North America (Halonen et al. 1998).

Notes. Shrubby thallus and presence of numerous isidia are similar to U. subfloridana. Pale base, slightly deformed main branches and lack of any papillae are the diagnostic features of U. hirta. Medullary chemistry (presence of fatty acids as main compounds) is helpful to verify identification. CleRC (2007) note that U. hirta lacks isidiomorphs, and that young fibrils can be mistakenly treated as isidiomorphs.

Ecology & distribution. Corticolous and lignicolous, prefers acid bark (foS & CleRC 2000). Reported in Europe: Albania, Austria, Belgium, Bulgaria, Czech Republic, Denmark, Estonia, Finland, France, Germany, Great Britain, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Netherlands, Norway, Poland, Portugal, Romania, Russia, Slovakia, Slovenia, Spain, Sweden, Switzerland and Ukraine.

Usnea intermedia (A. Massal.) JattaFlora Ital. Cryptog. 3: 145 (1909).—Usnea barbata var. intermedia A. Massal., Schedul.

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Critic. 3: 62 (1856).—Usnea carpatica Motyka, Lich. Gen. Usnea Stud. Monogr., Pars Syst. 2(1): 469 (1937).—Usnea faginea Motyka, Lich. Gen. Usnea Stud. Monogr., Pars Syst. 1: 172 (1936).—Usnea glauca Motyka, Lich. Gen. Usnea Stud. Monogr., Pars Syst. 1: 167 (1936).—U. hapalotera (Harm.) Motyka, Lich. Gen. Usnea Stud. Monogr., Pars Syst. 1: 235 (1936).—Usnea harmandii Motyka, Lich. Gen. Usnea Stud. Monogr., Pars Syst. 1: 163 (1936).—Usnea montana Motyka, Lich. Gen. Usnea Stud. Monogr., Pars Syst. 1: 234 (1936).—Usnea neglecta Motyka, Lich. Gen. Usnea Stud. Monogr., Pars Syst. 1: 179 (1936).—Usnea protea Motyka, Lich. Gen. Usnea Stud. Monogr., Pars Syst. 1: 232 (1936).—Usnea quasirigida Lendemer & I.I. Tav., Proc. Acad. Nat. Sci. Philadelphia 153: 179 (2003).—Usnea rigida Motyka, Lich. Gen. Usnea Stud. Monogr., Pars Syst. 1: 177 (1936), nom. illeg., non Usnea rigida Vainio (1901).—Usnea smaragdina Motyka, Lich. Gen. Usnea Stud. Monogr., Pars Syst. 1: 161 (1936).

Morphology. For a detailed description, see CleRC (1984a, 2007) and Halonen et al. (1998). Thallus shrubby to pendent; base pale or blackened; branches are irregularly swollen and may have foveoles and depressions on the surface; fibrils numerous; papillae abundant, verrucose or cylindrical; soralia and isidia absent; apothecia frequent, arising at apices of primary and secondary branches, with long marginal projections; ascospores 7.0–8.4 μm long. Cortex thin; medulla thin, loose.

Medullary chemistry. Chemotype (1) with salazinic acid (K+ yellow to red, Pd+ orange) as a main substance is known in Europe; chemotype (2) with protocetraric acid (K–, Pd+ orange) as a main substance is known in North America (Halonen et al. (1998); chemotype (3) without medullary compounds (K–, Pd–) has also been reported from North America (CleRC 2007).

Notes. Differs from another fertile European taxon, U. florida, by its subpendent to pendent thallus, medullary chemistry and shorter ascospores (8–11 μm long in U. florida).

Ecology & distribution. Corticolous, often on coniferous trees in submontane areas (wirth 1995a, b). Reported in Europe: Austria, Bulgaria, Czech Republic, Germany, Italy, Poland, Romania, Russia (central part and Caucasus), Slovakia, Slovenia, Switzerland, Spain and Ukraine.

Usnea lapponica Vain.Meddel. Soc. Fauna Fl. Fenn. 48: 173 (1925).—Usnea arnoldii Motyka, Lich. Gen. Usnea Stud. Monogr., Pars Syst. 1: 288 (1936).—Usnea fulvoreagens auct. non (Räsänen) Räsänen

Morphology. For a detailed description, see Halonen et al. (1998, 1999) and CleRC (2007). Thallus shrubby, richly branched, mainly anisotomic-dichotomous; branches often with depressions and foveolae; base pale to blackened; fibrils abundant; isidia always absent; papillae numerous; soralia large, becoming expanded and irregular or bracelet-like, flat to deeply concave, cortex around soralia is often torn. Cortex thin; medulla variable in thickness, loose to dense.

Medullary chemistry. (1) the main chemotype contains salazinic acid (K+ red, Pd+ yellow to orange) with different accessory substances (protocetraric, barbatic, caperatic acids) (Halonen et al. 1998); (2) chemotype with psoromic acid (K–, Pd+ yellow) is the rarest (Halonen et al. 1999); (3) chemotype without medullary compounds (K–, Pd–) is known both in Europe and North America.

Notes. For distinction from closely related taxa see under U. diplotypus.

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Ecology & distribution. Corticolous. Reported in Europe: Austria, Bulgaria, Czech Republic, Estonia, Finland, Germany, Italy, Latvia, Lithuania, Norway, Poland, Romania, Russia (northern and central parts, Caucasus), Slovakia, Slovenia, Spain, Sweden, Switzerland and Ukraine.

Usnea longissima Ach. Lichenogr. Univ.: 626 (1810).

Morphology. For a detailed description, see Halonen et al. (1998). Thallus pendulous, long to extremely long (up to 3 m); base pale to blackened; the main stem is only some mm long, covered with persistent cortex; numerous primary branches are almost undivided, with numerous perpendicular fibrils; papillae absent; isidia and soralia occasionally occur on side branches or fibrils. Cortex disintegrated on the primary branches exposing the thin compact medulla; central axis very thick, originally white but becoming pink to almost red or brown in decorticated branches. I+ blue reaction on the central axis is helpful in identification of juvenile specimens.

Medullary chemistry. Several chemotypes have been reported; diffractaic, evernic and barbatic acids (all react K–, Pd–) seem to be the commonest substances in U. longissima in Europe and North America (Halonen et al. 1998), while salazinic and fumarprotocetraric acids and atranorin are additionally known in Japan (aSaHina 1967).

Ecology & distribution. The species is distributed in the northern hemisphere, having circumboreal distribution pattern and occurring in humid forests, often near lakes or streams (nimiS 1993, BRodo et al. 2001). Corticolous, e.g. in eastern Fennoscandia it has been recorded on Picea and Betula (Halonen 1997); extremely sensitive to the changes of the environment (wirth 1995a, b). Reported in Europe: Austria, Bulgaria, Czech Republic (probably extinct), Finland, Germany, Italy, Latvia, Norway, Poland, Romania, Russia (northern and central parts, Caucasus), Slovakia (probably extinct), Slovenia, Spain, Sweden, Switzerland and Ukraine.

Usnea mutabilis Stirt.Scott. Naturalist 6: 107 (1881).—Usnea marocana Motyka, Lich. Gen. Usnea Stud. Monogr., Pars Syst. 2(1): 359 (1937).

Morphology. For a detailed description, see CleRC (1994, 2007) and CleRC & HeRReRa-CampoS (1997). Thallus shrubby to subpendent; base pale greenish or brownish; fibrils present, sparse; papillae absent; soralia punctiform, flat or slightly tubercular; isidia numerous. Cortex thin, glossy; medulla thin, dense, wine red.

Medullary chemistry. Chemotype (1) with fatty acids of the murolic acid complex (K–, Pd–) as main compounds (foS & CleRC 2000) is known in Europe; chemotype (2) with eumitrin A2 as a main compound and fatty acids of the murolic acid complex and norstictic acid as accessories were recently reported from Sonora, North America (CleRC 2007).

Notes. Morphologically and chemically resembles U. hirta (foS & CleRC 2000).

Ecology & distribution. Mainly corticolous, rarely saxicolous (CleRC & HeRReRa-CampoS 1997), prefers humid sites. In Europe it is present in the

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Mediterranean region only (foS & CleRC 2000). Reported in Europe: France, Italy, Portugal and Spain.

Usnea praetervisa (Asahina) P. ClercBibl. Lichenol. 88: 85 (2004).—Usnea comosa ssp. praetervisa Asahina, Lich. Jap. III. Genus Usnea: 95 (1956).—Usnea subfloridana ssp. praetervisa (Asahina) P. Clerc, Lichenologist 32: 83 (2000).

Morphology. For a detailed description, see CleRC (2004b, 2007). Thallus shrubby to subpendent, richly branched, mainly isotomic-dichotomous; base blackened, often with transverse annular cracks; fibrils present already on very young branches, acting like diaspores – fibrils are shed leaving small fibercles, while soredia and isidia may develop inside these fibercles; papillae present, predominantly on main branches; soralia minute, plane, later becoming confluent; isdia short, numerous on young soralia but present also on mature ones. Cortex rather thick; medulla thin and dense.

Medullary chemistry. Contains norstictic (K+ red, Pd+ yellow to orange) and connorstictic acids.

Notes. Morphologically similar to U. subfloridana, but differences in the development of soralia have been noticed (CleRC 2004b). Originally the taxon was described as having only different chemistry (norstictic acid, biosynthetically a distant medullary compound from thamnolic and squamatic acids, which are produced in U. subfloridana).

Ecology & distribution. Corticolous, on deciduous trees (Crataegus, Quercus) and on Erica (CleRC 2004). Reported in Europe: France (Corsica), Portugal and Spain.

Usnea rubicunda Stirt.Scott. Naturalist 6: 104 (1881).—Usnea protensa Stirt.—Usnea sublurida Stirt.

Morphology. For a detailed description, see CleRC (2007) and JameS et al. (2009). Thallus 3–10(–20) cm long, at first erect, later becoming pendulous; surface reddish-brown, more rarely greenish-grey with numerous red-brown flecks, especially at the basal part; base not blackened; branches may be segmented but not inflated; fibrils present, few to abundant; papillae and tubercles frequent on main branches; soralia punctiform, covered with abundant clustered isidia. Cortex thick, contains red pigment; medulla compact.

Medullary chemistry. Chemotype (1) with stictic acid (K+ yellow to red, Pd+ orange) as a main substance and norstictic and psoromic acids as accessories; chemotype (2) with salazinic (K+ red, Pd+ orange) acid as a main substance and norstictic acid as an accessory (JameS et al. 2009).

Notes. Usually easily recognized due to red-orange or reddish-brown thallus colour, but in some specimens the pigment is sparse or spotty and the basic colour of the thallus is grayish-green (BRodo et al. 2001; JameS 2003). Numerous isidia on minute soralia are also characteristic of this taxon. U. rubrotincta Stirt. (incl. U. rubescens Stirt.) and U. pensylvanica Motyka were considered synonyms to U. rubicunda by CleRC (2007), but molecular studies by oHmuRa (2008) support the monophyly of each species.

Ecology & distribution. Corticolous, on various deciduous trees and rarely on conifers, mostly on branches; occasionally on sandstone rocks (diedeRiCH

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et al. 2008). Grows in ancient woodlands or on isolated trees. Photophilous and hygrophilous, common in areas with an oceanic climate. In Europe it is the commonest Usnea species in the western part of the continent (foS & CleRC 2000). Reported in Europe: Albania, Austria, Belgium (probably extinct), Germany, Great Britain, Ireland, Italy, Luxembourg (probably extinct), Netherlands (probably extinct), Portugal, Russia (Caucasus), Slovakia (probably extinct), Slovenia and Spain.

Usnea schadenbergiana Göpp. & Stein60. Jahresber. Schles. Ges. Vaterl. Cult.: 229 (1883).—Usnea elongata Motyka, Lich. Gen. Usnea Stud. Monogr., Pars Syst. 2(1): 411 (1937).—Usnea hesperina Motyka, Lich. Gen. Usnea Stud. Monogr., Pars Syst. 2(1): 383 (1937).—Usnea subgracilis Vain., Ann. Acad. Sci. Fenn., Ser. A 6: 7 (1915).—Usnea subplicata (Vain.) Motyka, Lich. Gen. Usnea Stud. Monogr., Pars Syst. 2(1): 558 (1937).

Morphology. For a detailed description, see CleRC (1997, 2007), Halonen et al. (1998) and HeRReRa-CampoS et al. (1998) (also under the name U. hesperina). Thallus pendulous; base pale; branches even in thickness, slendering evenly towards the apices, without foveolae and/or ridges; distinctly segmented by annular cracks close to the base; fibrils present, often long and curved, sparse to abundant; papillae absent; soralia present, punctiform, slightly tuberculate, mostly immature and resembling pseudocyphellae; isidia small, on young soralia only. Cortex mat, relatively thick; medulla thin and compact; central axis thick.

Medullary chemistry. Chemotype (1) with protocetraric acid only (K+ yellow, Pd+ orange) occurs widely in Europe, North and South America, and Africa; chemotype (2) with stictic acid complex has been reported from Asia (CleRC 1997) and the Caribbean Islands (CleRC 2007).

Ecology & distribution. Corticolous, on deciduous (e.g. Laurus, Quercus) or coniferous trees (Picea, Tsuga), rarely on rocks (Halonen et al. 1998, HeRReRa-CampoS et al. 1998). Reported in Europe: France and Slovenia (specimens from Spain have been re-identified by Arroyo & Seriñá, in litt.).

Usnea silesiaca MotykaWydaw. Muz. Slask. Katowicach Dzial 3(2): 19 (1930).—Usnea madeirensis Motyka, in Tavares, Revista Biol. (Lisbon) 4: 131–134 (1964).

Morphology. For a detailed description, see CleRC (1991, 2007), Halonen et al. (1998) and JameS et al. (2009) (also under the name U. madeirensis). Thallus 6–12 cm long, shrubby, erect to pendulous, richly branched, branches somewhat interwoven; base thick, extensively blackened, with numerous annular cracks which may occur also in distant parts of the main branches; branches tapering; fibrils present, few to numerous; papillae present, dense on basal parts of main branches; soralia conspicuous, punctate to transversely elliptical to irregularly rounded, remaining discrete; isidia irregularly present, but usually absent on mature soralia. Cortex very thick (9–14%), mat; medulla very thin (7–12%) and compact.

Medullary chemistry. Contains salazinic (K+ yellow to red, Pd+ orange) acid as a main substance.

Ecology & distribution. Mainly corticolous, on various deciduous trees and, rarely, on rocks. Reported in Europe: Austria, Belgium (probably extinct), France,

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Germany, Great Britain, Italy, Luxembourg (probably extinct), Norway (southern part only), Poland, Portugal, Russia (Caucasus), Spain, Sweden (southern part only), Switzerland and Ukraine.

Usnea sphacelata R. Br.Chloris Melvilliana: 49 (1823).—Neuropogon sphacelatus (R. Br.) D.J. Galloway, DSIR Land Resources Scientific Report 26: 7 (1992).—Usnea sulphurea (J. König) Th. Fr. (1867), nom. illeg.

Morphology. For a description of traditional treatment, see waLker (1985). Thallus up to 4 cm long, shrubby, erect, attached to the substratum by a holdfast; pale to bright yellow with distinct black bands, base yellow, terminal parts of the branches mostly black; main branches terete and smooth or verruculose and scabrid; annular cracks occasional; fibrils absent; papillae minute, may be pigmented; soralia conspicuous, rounded, mostly black, becoming convex and eroded; isidia usually absent. Apothecia not seen. Cortex consists of pachydermatous, strongly conglutinated hyphae with mainly radial orientation (oHmuRa & kanda 2004); medulla thick, loose; axis comparatively thin, ≤ 50% (SeymouR et al. 2007).

Medullary chemistry. Chemotype (1) with norstictic acid (K+ red, Pd+ orange) is reported from Antarctica (THomSon 1984); chemotype (2) without medullary compounds is more widely distributed.

Notes. This is the only neuropogonoid species in Europe, the group being distinguished from other Usnea species by several unique features, such as the presence of a black pigment in the thallus, a dark brown apothecial disc and mainly saxicolous habitat. The group has been recognized as an independent genus or as subgenus or section within Usnea; however, phylogenetic analyses have demonstrated the polyphyletic character of the group (wirtz et al. 2006, 2008). Recent molecular studies (SeymouR et al. 2007, wirtz et al. 2008) revealed that U. sphacelata is also heterogenous and the material traditionally assigned to the taxon, is in fact related to U. perpusilla. Formal recombinations and descriprions of new species are expected.

Ecology & distribution. Grows on rocks, preferably granitic or basaltic; distribution characteristically bipolar – known both in the Arctic (almost circumpolar) and the Antarctic (Antarctic Peninsula, high Andean regions of South America, and the South Island of New Zealand) (SeymouR et al. 2007). Reported in Europe: Greenland, Iceland, Russia (Arctic islands), Svalbard.

Usnea subcornuta Stirt.Scott. Naturalist 6: 107 (1881).

Morphology. Thallus shrubby to subpendent; lateral branches lightly constricted at the point of attachment, branches with annular cracks; base pale; fibrils present, scarce to abundant; papillae absent; soralia usually large, with numerous isidia. Cortex glossy; medulla loose, contains subcortically (under the cortex) an orange pigment.

Medullary chemistry. Contains stictic (K+ yellow to red, Pd+ orange) and norstictic acids as main substances (foS & CleRC 2000).

Notes. Considered as a synonym of U. cornuta, but CleRC (1987b) indicated that this is a distinct species characterized by the presence of orange pigment

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under the cortex. Morphologically similar to U. flammea (foS & CleRC 2000) and probably belongs to the U. fragilescens aggregate.

Ecology & distribution. Corticolous, on deciduous trees (e.g. Quercus suber), mostly on exposed branches of young trees (foS & CleRC 2000). A rare species, known in Europe from a few southern localities only. Reported in Europe: Portugal, Russia (Caucasus) and Spain.

Usnea subfloridana Stirt.Scott. Naturalist 6: 294 (1882).—Usnea comosa (Ach.) Vain., Meddel. Soc. Fauna Fl. Fenn. 48: 173(1925), nom. illeg., non Usnea comosa Pers.—Usnea similis (Motyka) Räsänen, Ann. Acad. Sci. Fenn., Ser. A4, 34(4): 19 (1931).

Morphology. For a detailed description, see Halonen et al. (1998, 1999). Thallus shrubby to subpendent, richly branched, mainly isotomic-dichotomous; base blackened, often with transverse annular cracks; fibrils present, abundant near the base and sparse terminally; isidia and papillae usually numerous; soralia vary from punctiform to enlarged and typically bear short isidia. Cortex rather thick; medulla thin and dense.

Medullary chemistry. Three chemotypes are reported: (1) with squamatic acid (K–, Pd–, UV+ whitish blue) as a main substance; (2) with thamnolic acid (K+ yellow, Pd+ orange) as a main substance; (3) with both squamatic and thamnolic acids (Halonen et al. 1998, 1999). Alectorialic acid may occur as an accessory.

Notes. Usually easily recognized by its black base and presence of numerous isidia. Sometimes may be confused with U. diplotypus or U. wasmuthii, then the identification of medullary substances can help – squamatic or thamnolic acids which are the main compounds in U. subfloridana are usually absent in U. diplotypus and U. wasmuthii, except the chemotype (4) of the latter.

Ecology & distribution. Corticolous, occasionally also lignicolous or on rocks. Reported in Europe: Austria, Belgium, Bulgaria, Czech Republic, Denmark, Estonia, Faeroe Islands, Finland, France, Germany, Great Britain, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Netherlands, Norway, Poland, Portugal, Romania, Russia, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland and Ukraine.

Usnea subscabrosa MotykaLich. Gen. Usnea Stud. Monogr., Pars Syst. 2(1): 313 (1937).

Morphology. For a detailed description, see CleRC (1992, 2007) and HeRReRa-CampoS et al. (1998). Thallus erect, subpendent to pendent, up to 25 cm long, stiff; base pale or red-brown pigmented; branches even in thickness, slendering evenly towards the apices, not constricted at the point of attachment; fibrils usually absent, occassionally scarce, rarely numerous; papillae absent or present, verrucous; soralia present, punctiform to somewhat enlarged (less than half width of branch bearing them), mainly on small branches and the apices; isidia absent to abundant (on young soralia). Cortex very thick (9–17%), characteristically shiny; medulla thin, compact.

Medullary chemistry. Chemotype (1) with protocetraric acid (K–, Pd+ orange) as a main substance and fumarprotocetraric and barbatic acids as accessories (HeRReRa-CampoS et al. 1998); chemotype (2) with thamnolic acid

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as a main substance (K+ yellow to slowly red, P+ orange) and squamatic acid as an accessory has been reported from Azores (CleRC 2006).

Notes. Morphologically very variable species (the characters which mainly vary being growth habit from shrubby to pendulous, presence and abundance of fibrils, papillae and isidia, shape of soralia); important diagnostic characters include the very thick and vitreous cortex, and protocetraric acid as a main medullary substance.

Ecology & distribution. Both corticolous and saxicolous; moderately acidophilous, anitrophilous and toxitolerant (foS & CleRC 2000). Distributed in south-western areas of Europe. Reported in Europe: Great Britain (Cornwall), Italy, Portugal and Spain.

Usnea substerilis MotykaWydaw. Muz. Slask. Katowic. 3(2): 24 (1930).—Usnea sorediifera Motyka, Wydaw. Muz. Slask. Katowic. 3(2): 24 (1930), nom. illeg., non Usnea sorediifera (Arnold) Lynge (1921).—Usnea stuppea (Räsänen) Motyka

Morphology. For a detailed description, see Halonen et al. (1998, 1999) and CleRC (2007). Thallus shrubby, usually short, richly branched, mainly anisotomic-dichotomous; base greenish or brownish to blackened; branches of uneven thickness, may be irregularly deformed, swollen and foveolate, with annular cracks which may have white medullary rings; fibrils present, sometimes abundant also terminally; isidia short, present at least on young soralia (and abraded on mature soralia); papillae numerous; soralia irregular, slightly tuberculate to slightly excavate, with granulose soredia. Cortex thin; medulla variable in thickness and density.

Medullary chemistry. (1) the main chemotype contains salazinic acid (K+ red, Pd+ yellow to orange) with different accessory substances (protocetraric, barbatic, 4-O-demethylbarbatic acids); (2) chemotype without medullary compounds (K–, Pd–) is also known (Halonen et al. 1998).

Notes. For distinction from closely related taxa see under U. diplotypus.Ecology & distribution. Corticolous both on coniferous and on deciduous

trees. Reported in Europe: Austria, Bulgaria, Estonia, Finland, Germany, Italy, Latvia, Lithuania, Norway, Poland, Romania, Russia (northern part and Caucasus), Slovakia, Spain, Sweden, Switzerland and Ukraine.

Usnea wasmuthii RäsänenAnn. Acad. Sci. Fenn., Ser. A4, 34(4): 19 (1931).

Morphology. For a detailed description, see CleRC (1992, 2007) and Halonen et al. (1999). Thallus shrubby or rarely subpendent, rather richly branched, branches gradually tapering; branching mainly isotomic-dichotomous; base distinctly blackened, often with both transverse and longitudinal cracks; fibrils present, but usually few near apices; isidia short, few, present on young soralia (and abraded on mature soralia); papillae present; soralia small to enlarged, oblong-cylindrical, slightly excavate. Cortex thick; medulla thin, dense.

Medullary chemistry. Five chemotypes have been reported (CleRC 1992; Halonen et al. 1999; foS & CleRC 2000; oHmuRa 2001): (1) chemotype with barbatic acid (K–, Pd–) as the main substance; (2) chemotype with salazinic acid (K+ red, Pd+ yellow to orange) as the main substance; (3) chemotype with both

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barbatic and salazinic acids (K+ red, Pd+ yellow to orange) as main substances; (4) chemotype with thamnolic acid (K+ yellow, Pd+ orange) as the main substance; (5) chemotype without medullary compounds (K–, Pd–). Different accessory compounds (protocetraric, 4-O-demethylbarbatic, psoromic acids) may occur in chemotypes (1) and (2), and squamatic acid additionally in the chemotype (4); the latter (recorded in Japan and Spain) has also been considered a possible hybrid, since thamnolic and squamatic acids are typical compounds for U. subfloridana.

Notes. For distinction from closely related taxa see under U. fulvoreagens.Ecology & distribution. Corticolous. Reported in Europe: Austria, Belgium

(probably extinct), Bulgaria, Estonia, Finland, Germany, Great Britain, Hungary, Ireland, Italy, Lithuania, Luxembourg, Netherlands, Norway, Poland, Romania, Russia (northern and central parts, Caucasus), Slovakia, Spain, Sweden and Switzerland.

Acknowledgements

The authors thank the curators of the herbaria who made their specimens available and all those fellow lichenologists who sent valuable remarks for improving the (interactive) key. Special thanks go to Teuvo Ahti, James Lendemer, Thorsten Lumbsch and Christoph Scheidegger for useful comments and support; criticism from Philippe Clerc is also acknowledged. Mark Seaward is sincerely thanked for revising the English. The key was prepared in the framework of the project KeyToNature. Financial support was received from the Estonian Science Foundation (grant no 7470), from the Estonian Ministry of Education and Research (targeted financing no 0153), from the Norwegian Financial Mechanisms and EEA Financial Mechanisms (grant EMP9) and from the European Union through the European Regional Development Fund (Center of Excellence FIBIR).

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