[BGBM-Logo] Lichen determination keys
- neotropical Stereocaulon -		 [BGBM-Foto klein]

Key to the Stereocaulon species in the Neotropics

by H. Sipman, 27 Aug. 2002 / general remarks

1a Pseudopodetia absent; thallus consisting only of phyllocladia directly attached to the substrate, up to a few mm tall (primary thallus) --- 2
1b Pseudopodetia present, usually over 1 cm tall, up to over 10 cm; primary thallus present or absent --- 3

2a Phyllocladia wart-like to short-cylindrical, ca. 0.4 mm wide and up to 1 mm tall, with apical soralia (Atranorin, lobaric acid; cephalodia spherical; Brazil, Minas Gerais, 2200 m; widespread in temperate areas of the world.) --- S. pileatum Ach.
2b Phyllocladia scale-like, scales to ca. 2 mm wide and long, with crenate margin, growing in several tiers on top of each other to ca. 10 mm, without soralia (Atranorin, norstictic, stictic acid agg.; cephalodia spherical; Galapagos; 500-1000 m; endemic; this lichen reminds much of the Cladonia miniata group, with a different chemistry.) --- S. azulense Yoshim. & W.A. Weber

3a Phyllocladia cylindrical, more or less branched, sometimes blending into pseudopodetium branches, sometimes scarce --- 4
3b Phyllocladia granular to wart-like, peltate or scale-like --- 20

4a Soredia (ca. 50 mu wide) or soredium-like (corticate) granules (ca. 100 mu wide) present --- 5
4b Soredia and soredium-like granules absent --- 14

5a Soredium-like granules present, usually at the tips of the pseudopodetia --- 6
5b Farinose soredia present, usually over larger areas or at the tip of the pseudopodetia --- 8

6a Cephalodia slightly pruinose; didymic acid present (Atranorin, didymic acid with a trace of stictic acid; cephalodia sacculate; Ecuador, Colombia, Venezuela, Costa Rica; 1700-2500(-3400) m; restricted to the neotropics.) --- S. didymicum I.M. Lamb
6b Cephalodia not pruinose; didymic acid absent --- 7

7a Stictic acid present (Atranorin, stictic acid and satellite substances, sometimes with traces of norstictic, perlatolic (sometimes dominant), anziaic, glomelliferic, bourgeanic acids; cephalodia sacculate; Brazil, Bolivia, Peru, Ecuador, Colombia, Venezuela, Costa Rica, El Salvador, Mexico, Galapagos; (700-)1100-2400(-3700) m, lowest elevations in SE Brazil; restricted to the neotropics but also reported from Tahiti.) --- S. microcarpum Müll. Arg.
7b Protocetraric acid present (Atranorin, protocetraric, traces of perlatolic (sometimes dominant) or lecanoric, traces etc.; cephalodia sacculate; Peru, Ecuador, Colombia, Venezuela, Mexico; 2500-4500 m; restricted to the neotropics.) --- S. pachycephalum Vain.

8a Soralia on the underside of flattened, slanting pseudopodetium tips; cephalodia composed of one or more elongate, finger-like branches, rather like the phyllocladia but darker grey (Atranorin, porphyrilic acid; cephalodia sacculate; primary thallus persistent; Brazil (Itatiaia), Bolivia, Peru. Ecuador, Colombia, Venezuela, Costa Rica, Mexico, Dominican Republic; 1800-3800 m; restricted to the neotropics; sorediate individuals are treated as var. compressum (Nyl.) I.M. Lamb.) --- S. strictum Th. Fr.
8b Soralia on all sides of erect pseudopodetium tips or spreading over large parts of the pseudopodetia; cephalodia globose, very different from the phyllocladia --- 9

9a Cephalodia bluish or brownish, translucent when wet, completely gelatinous internally (protosacculate) (Atranorin, stictic, norstictic; Bolivia, Ecuador, Colombia, Costa Rica, Mexico; 3450-4300 m; restricted to the neotropics and Africa.) --- S. claviceps Th. Fr.
9b Cephalodia greyish, not translucent and with non-gelatinous, aerated parts internally (sacculate) --- 10

10a Phyllocladia hardly developed, pseudopodetia largely sorediate; cephalodia densely verrucose; rangiformic acid dominant lichen substance (Atranorin, rangiformic, norrangiformic acid; cephalodia sacculate; Colombia, Costa Rica; 3350-3750 m; widespread over the world.) --- S. delisei Bory
10b Phyllocladia distinct, at least in the lower parts of the pseudopodetia; soredia apical on the pseudopodetia, sometimes spreading further downward; cephalodia with smooth or somewhat folded surface; stictic or perlatolic acid dominant lichen substance --- 11

11a Soredia spread over upper parts of pseudopodetia and terminal branchlets --- 12
11b Soredia concentrated in swollen, apical structures consisting of soredia mixed with tiny branchlets --- 13

12a Phyllocladia present only at the base of the pseudopodetia (Atranorin, stictic acid and associated substances, sometimes with minor quantities of norstictic, perlatolic, ursolic acids; in Colombia also a strain with atranorin and perlatolic acid only; cephalodia sacculate; Bolivia, Peru, Ecuador, Colombia, Venezuela, Costa Rica; 2000-4300 m; restricted to the neotropics, the Atlantic Islands and Africa; Colombian reports of S. corticatulum Nyl. concern stunted plants of this species.) --- S. atlanticum (I.M. Lamb) I.M. Lamb
12b Phyllocladia present over the whole pseudopodetia, shorter towards the tips (Atranorin, perlatolic acid; cephalodia sacculate; Bolivia, Peru, Ecuador, Colombia, Venezuela, Mexico; 3000-4300 m.; restricted to the neotropics, southern South America and Africa.) --- S. meyeri Stein

13a Soralia irregularly lobed, sorediate and greenish outside (Atranorin, perlatolic acid, sometimes with a trace of anziaic acid; cephalodia sacculate; Peru, Ecuador, Colombia, Costa Rica; 3400-4340 m; restricted to the neotropics.) --- S. crambidiocephalum I.M. Lamb
13b Soralia rounded, covered by peltate, brownish plates and smooth outside (Atranorin, perlatolic acid; cephalodia sacculate; Colombia, Ecuador; 3750-4300 m; endemic.) --- S. globisorum Sipman

14a (4) Phyllocladia with greenish-grey, flattened upper side and whitish to pale brownish, convex lower side, most distinctly so towards the base of the pseudopodetia, not blending into pseudopodetia (Atranorin, stictic acid with minor quantities of norstictic, menegazziaic, cryptostictic and constictic acids, sometimes norstictic acid dominant; cephalodia spherical; Costa Rica, Nicaragua, West Indies (a.o. Dominica, Guadeloupe, Puerto Rico, Saba); 700-1300 m; restricted to the neotropics.) --- S. virgatum Ach.
14b Phyllocladia of similar shape and colour on all sides, truly cylindrical --- 15

15a Cephalodia completely gelatinous, bluish to brownish and more or less translucent (spherical), usually between short pseudopodetia on the ground; pseudopodetia rarely over 1(-2) cm tall (Atranorin, lobaric acid; apothecia terminal, large, to 3 mm wide; primary thallus persistent; Bolivia, Peru, Ecuador, Colombia, Mexico; 3650-4800 m; widespread in the world.) --- S. glareosum (Sav.) H. Magn.
15b Cephalodia with differentiated cortex and aerated parts, always opaque and grey (sacculate or protosacculate); pseudopodetia usually over 2 cm tall. --- 16

16a Cephalodia composed of one or more elongate, finger-like branches, not unlike the phyllocladia but darker grey (Atranorin, porphyrilic acid; cephalodia sacculate; apothecia terminal, to 1.5 mm wide, with black disc; primary thallus persistent; Brazil (Itatiaia), Bolivia, Peru. Ecuador, Colombia, Venezuela, Costa Rica, Mexico, Dominican Republic; 1800-3800 m; restricted to the neotropics; fertile individuals of this species tend to be non-sorediate and are treated as var. strictum, they are much less common and seemingly of restricted distribution.) --- S. strictum Th. Fr.
16b Cephalodia clavate to globose --- 17

17a Cephalodia gelatinous throughout, globose, often of waxy appearance (protosacculate); stictic or norstictic acid present (Atranorin, with norstictic acid or with stictic acid and its satellites, usually with a trace of norstictic acid; Peru, Ecuador, Colombia, Venezuela, Mexico; (1500-)2700-3800 m; widespread in the tropical mountains world-wide.) --- S. pomiferum P.A. Duvign.
17b Cephalodia with aerated tissue, grey and opaque (sacculate); stictic acid absent --- 18

18a Cephalodia with white ridges (Atranorin, perlatolic acid with traces of protocetraric and sometimes anziaic acid; cephalodia sacculate; Ecuador, Colombia; 2100-3750 m; endemic.) --- S. novogranatense I.M. Lamb
18b Cephalodia uniformly grey-coloured --- 19

19a Thallus P+ red; protocetraric acid present; known only from Cerro Duida-Marahuaca, Amazonas, Venezuela, at about 800 m (Protocetraric and succinprotocetraric acids; cephalodia sacculate; Venezuela - Amazonas; ca. 750 m; endemic.) --- S. follmannii V. Marcano, A. Morales et Galiz
19b Thallus P- or P+ yellowish; protocetraric acid absent; common and widespread above ca. 2000 m (Atranorin, perlatolic acid, often with a trace of anziaic acid; cephalodia sacculate; Brazil, Bolivia, Peru, Ecuador, Colombia, Venezuela, Costa Rica, Mexico, Cuba, Dominican Republic, Puerto Rico; (1000-)1900-4000(-4500) m, lowest elevations in SE Brazil; widespread in the southern hemisphere and the neotropical mountains.) --- S. ramulosum (Sw.) Räusch.
19c Species characterised by soredium-like granules may key out here, when the granules are scarce or fallen off. They grow generally at lower elevation, below 2500 m, and have darker brown apothecia and different chemical patterns --- 6

20a (3) Phyllocladia much elongated, to over 1 mm long and divided into ca. 0.2 mm wide slips, subcylindrical above and more distinctly foliose at the base of the pseudopodetium (Atranorin, stictic acid with minor quantities of norstictic, menegazziaic, cryptostictic and constictic acids, sometimes norstictic acid dominant; cephalodia spherical; Costa Rica, Nicaragua, West Indies (e.g. Dominica, Guadeloupe, Puerto Rico, Saba); 700-1300 m; restricted to the neotropics.) --- S. virgatum Ach.
20b Phyllocladia more or less wart-like, mostly shorter than wide, occasionally near the base of the pseudopodetium more pronouncedly foliose --- 21

21a Phyllocladia wart-like blending over the whole pseudopodetia into minutely scale-like, ca. 0.2-0.4 mm wide, deeply crenate or with elongate lobules, uniformly coloured --- 22
21b Phyllocladia wart-like blending towards the base of the pseudopodetia into peltate or scale-like, then with distinct, pale margins --- 24

22a Podetia covered with thick felt layer covering the cephalodia; apothecia usually small, under 1 mm wide, numerous on short subapical branchlets; pseudopodetia P+ orange, K+ orange (stictic acid present); widespread (Atranorin, stictic acid and its satellites, often with traces of norstictic acid; cephalodia spherical; Bolivia, Peru, Ecuador, Colombia, Venezuela, Costa Rica, Mexico, Dominican Republic; (2300-)2500-4400 m; widespread in the world; S. myriocarpum Th. Fr. is included here because the differentiating characters, thinner and smoother tomentum, more developed cephalodia (subglobose, botryose-divided, bluish-grey), do not allow a clear separation in the available material.) --- S. tomentosum Fr.
22b Podetia with scarce felt leaving the (scarce) cephalodia free; apothecia larger, to ca. 2 mm wide, with few at the pseudopodetium tips; pseudopodetia P- or P+ pale yellowish, K+ pale yellow (stictic acid absent); from Peru southward --- 23

23a Cephalodia inconspicuous, pale grey and rounded (Atranorin, lobaric acid (rarely absent); cephalodia spherical; Peru; widespread in the temperate and cold zones of the world, reaching the tropics only in Peru.) --- S. alpinum Laurer
23b Cephalodia conspicuous, black and with rough surface, abundant near the tips of the podetia (Atranorin, lobaric acid; cephalodia spherical, containing Stygonema, not Nostoc, as photobiont; Peru; 2500 m; widespread in the temperate and cold zones of the world, reaching the tropics only in Peru.) --- S. paschale Ach.

24a Basal phyllocladia distinctly scale-like, with whitish margins, not peltate; podetia erect and largely unbranched, often with numerous tiny apothecia on short lateral branches (Atranorin, stictic acid and its satellites, often with a trace of norstictic acid; cephalodia spherical; Venezuela, Costa Rica, Greater Antilles (Cuba, Jamaica); 1300-1400 m; restricted to the neotropics.) --- S. cornutum Müll. Arg.
24b Basal phyllocladia peltate or wart-like --- 25

25a Upper half of pseudopodetia bearing ca. 0.5 mm wide granules, larger phyllocladia only present in lower half; only known from the Galapagos Islands, below 1000 m (Atranorin, lobaric acid; cephalodia spherical; Galapagos Islands; 800 m; endemic.) --- S. weberi I.M. Lamb
25b Granules absent or restricted to pseudopodetium tips, rest bearing over 0.1 mm wide, wartlike or peltate phyllocladia; widespread in high mountains above 2500 m --- 26

26a Peltate phyllocladia numerous at pseudopodetium base and sometimes higher up --- 27
26b Peltate phyllocladia (almost) absent, basal phyllocladia warty --- 28

27a Phyllocladia P+ orange, K+ orange (stictic acid present) (Atranorin, stictic acid and its satellites, often with a trace of norstictic acid; cephalodia spherical; Bolivia, Peru, Ecuador, Colombia, Venezuela, Costa Rica, Mexico, Dominican Republic; 2100-4500 m; common in temperate and cold areas worldwide; a variable species as regards soredium production and ramification; preferably on volcanic rock, on sandstone often replaced by S. pityrizans.) --- S. vesuvianum Pers.
27b Phyllocladia P- or P+ pale yellowish, K+ pale yellow (stictic acid absent) (Atranorin, lobaric acid (sometimes absent); cephalodia spherical; Ecuador, Panama, Costa Rica, Guatemala; (1700-)3300-4000 m; restricted to the neotropics.) --- S. obesum Th. Fr.

28a Apothecia to 2.5 mm wide, with black disc and prominent, pale margin; pseudopodetia erect (Bolivia, Peru, Colombia, Venezuela, Costa Rica; 2200-3500(-4000) m; atranorin, stictic, norstictic; cephalodia spherical; restricted to the neotropics.) --- S. pityrizans Nyl.
28b Apothecia to 0.5 mm wide, brown with inconspicuous margin; pseudopodetia often creeping (Atranorin, stictic acid and its satellites, usually with a trace of norstictic acid; cephalodia spherical; Ecuador, Colombia; 3400-4500 m; restricted to southern South America, but extending northwards along the Andes; in the Neotropics mainly in a creeping form growing loosely over the soil (var. surreptans (I.M. Lamb) I.M. Lamb).) --- S. verruciferum Nyl.

General remarks / key

After my plan for a treatment of Neotropical Stereocaulon was put on ice (there is little to add to Lamb's treatment!), I present here the information gathered so far in the form of an identification key. It is based on the literature cited below and on specimens in herbarium B.

Most Stereocaulon species have a shrub-like, strongly branched thallus. The branches have a woody medulla initially covered by an outer layer containing the photobionts and a cortex. They soon become denudated of this layer, and the photobiont is contained in specialised, rather clearly differentiated branchlets called phyllocladia. They may be cylindrical, wart-like or more or less scale-like. In the latter case they remind of the genus Cladonia, and in analogy of this genus, the fruticose, non-photosynthesizing parts are called pseudopodetia.

The juvenile stage of the pseudopodetia resembles phyllocladia. In some species the substrate is extensively covered with swarms of such phyllocladia, called primary thallus, surrounding the more mature, fruticose pseudopodetia, like in S. strictum. In most species there are no such swarms and the populations in the field are dominated by tufts of shrubby pseudopodetia. In a few species the primary thallus does not develop into pseudopodetia but remains low, up to few mm tall, .e.g. in S. pileatum. S. glareosum is intermediary, with short pseudopodetia mixed with primary thallus.

Most Stereocaulon species have cephalodia. These contain the cyanobacterium Nostoc as photobiont in all neotropical species except S. paschale. With increasing complexity three types can be distinguished:

- spherical, consisting of a more or less globose, gelatinous mass of Nostoc colonies containing bundles of fungal hyphae. Such cephalodia have a brownish to blackish colour and are translucent, at least when wet.

- protosacculate, with more differentiated fungal tissue forming a cortical layer surrounding the gelatinous Nostoc colonies. These have a more or less blue-grey colour, with somewhat waxy appearance.

- sacculate, like the preceding, but with medullary, air-containing tissue between the gelatinous Nostoc colonies. These have a paler grey colour, without waxy appearance.

The morphological characters of the species are often poorly expressed, and a chemical analysis is often highly desirable for certain identification.

The species grow on siliceous, more or less weathered rock in humid, sheltered but sufficiently light sites. Common habitats are stones and gravel on the soil in low and open vegetation, and road banks. Most species are restricted to high elevations, above ca. 3000 m. Some descend to below 2000 m, mainly on man-made clearings. Remarkably low occurrences are found in the Caribbean and the Galapagos Archipelago, where Stereocaulon may grow well below 1000 m elevation.

References:

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