TWO NEW SOREDIATE TAXA OFPELTIGERA

Lichenologist 27(1): 43–58 (1995)

TWO NEW SOREDIATE TAXA OF PELTIGERA B. GOFFINET* and R. I. HASTINGS*‡

Abstract: Examination of specimens of Peltigera didactyla, from Africa, Asia, Europe and North America revealed that this sorediate species includes three entities that can be separated on morphological characters. A new species, P. lambinonii, is described from East Africa, and a new combination P. didactyla var. extenuata, is proposed to accommodate morphs from mesic forest habitats in Asia, Europe and North America. Despite this taxonomic reduction, P. didactyla var. didactyla remains a ubiquitous taxon. The former two taxa often produce methyl gyrophorate, which can co-occur with traces of gyrophoric acid. These tridepsides were only rarely detected in var. didactyla; their occasional presence seems to be best explained by hybridization. The taxonomic and ecological significance of these substances is discussed.

Introduction When Gyelnik (1933) attempted to provide a key to all known species of Peltigera, he accepted four taxa with laminal soredia: P. erumpens (Tayl.) Elenkin, P. hazslinszkyi Gyelnik in Anders, P. leptoderma Nyl. and P. ulcerata Müll. Arg., the last species being restricted to the Southern Hemisphere. Peltigera canina (L.) Willd. var. extenuata Nyl. ex Vainio, a sorediate, broadly lobate taxon described from Finland (Vainio 1878) was considered synonymous with P. erumpens by Gyelnik (label annotations from September 1927 on type specimen of extenuata). Peltigera spuria (Ach.) DC. included small esorediate tomentose specimens with erect lobes bearing apothecia. The observation of Dahl (1950) on the development of one individual thallus showed that the sorediate form P. erumpens is not a distinct species but a juvenile stage of P. spuria and that P. hazslinszkyi was in fact an intermediate stage of the two. In his North American revision of the genus, Thomson (1950) considered P. spuria as a variety [P. canina (L.) Willd. var. spuria (Ach.) Schaerer], and all sorediate taxa known from the Northern Hemisphere as growth forms (P. canina var. spuria f. sorediata Schaerer). However, his concept did not withstand more recent treatments (Kurokawa et al. 1966; Ozenda & Clauzade 1970; Vitikainen 1981; Purvis et al. 1992). Peltigera didactyla (With.) Laundon (the earlier name for P. spuria, see Laundon 1984) produces soredia in the early stages of development ‘but as fruiting bodies are formed the soralia are reduced so that old fruiting thalli are devoid of soralia’ (Jahns 1973). This concept is now widely accepted in Europe (e.g. Ozenda & Clauzade 1970; Wirth 1980; Vitikainen 1981; Purvis et al. 1992). However, in North America, Thomson (1984) still considered *Botany Department, The University of Alberta, Edmonton, Alberta, Canada T6G 2E9. ‡Provincial Museum of Alberta, Natural History Section, 12845 102 Avenue, Edmonton, Alberta, Canada T5N 0M6. 0024–2829/95/010043+16 $08.00/0

? 1995 The British Lichen Society

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P. didactyla at the infraspecific level [P. canina (L.) Willd. f. sorediata Schaerer] whereas Weber (1990) accepted P. erumpens (defined by small cup-shaped sorediate thalli) as distinct from P. didactyla. Recent studies on thallus formation of P. didactyla, however, reveal that the soredia develop into small cup-shaped thalli that can produce soredia when about 5 months old, resume growth, and then develop fruiting bodies (Stocker-Wörgötter & Türk 1990). Therefore, P. erumpens must be considered as a stage in the life cycle of P. didactyla and is not worthy of taxonomic recognition, as was suggested by Lambinon (1966), Hawksworth et al. (1980) and Vitikainen (1981). Consequently, P. erumpens should be deleted from the North American checklist of Egan (1991). The type of P. didactyla (OXF) represents a mature thallus with erect fertile lobes and soredial scars at their base (note: the type specimen was not available for study and our observations are based solely on photographs provided by OXF). The genus Peltigera is at present characterized by the absence of positive spot tests, but several species, especially in the P. polydactyla group, produce numerous triterpenoids and tridepsides (Vitikainen 1981). In the P. canina group, including the taxa with appressed tomentum and cyanobacterial photobiont, only P. retifoveata Vitik. from the Northern Hemisphere is so far known to invariably produce the depsides tenuiorin, and methyl gyrophorate (in trace amounts) &gyrophoric acid, and the triterpenoid hopanes zeorin and dolichorrhizin (Vitikainen 1985). Peltigera didactyla is said to be a ubiquitous species that occurs on most continents (Thomson 1950; Kurokawa et al. 1966; Vitikainen 1981; Awasthi & Joshi 1982; Galloway 1985; Wirth 1987; Swinscow & Krog 1988). According to Culberson (1969, 1970), based on reports from Germany, Japan and North America, P. didactyla does not produce lichen substances. In New Zealand, identical observations were made by Galloway (1985). However, from East Africa, Swinscow & Krog (1988) reported methyl gyrophorate and gyrophoric acid in the soralia of P. didactyla. During a revision of the genus Peltigera in Alberta, Canada (Goffinet & Hastings 1994) several specimens of P. didactyla could be segregated based on their broad, spreading lobes, and their lower surface with pale veins throughout and numerous, fibrillose rhizines. Such thalli typically grow in mesic forested sites. Morphologically, they contrast well with specimens from disturbed open localities. The latter, typical P. didactyla, are often reduced to a small, deeply concave thallus that grows into erect fertile lobes and their veins typically darken towards the centre, where their mostly simple rhizines are concentrated. In addition, specimens from mesic sites appear to produce methyl gyrophorate&gyrophoric acid in all or at least some, mostly sorediate, parts of their thallus. By contrast, specimens from drier sites are typically lacking such tridepsides. Examination of material from Europe revealed that this pattern is widespread. The African material of P. didactyla s. lat., can be segregated in a similar fashion. Here, however, typical P. didactyla contrasts with rather broadly lobate specimens, the lower surface of which bears a dense mat of abundantly branched dark brown rhizines. These specimens further produced methyl gyrophorate&gyrophoric acid in their soralia, whereas typical African P. didactyla also lacked such tridepsides.

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Examination of specimens from Asia, East Africa, Europe and North America, led us to consider P. didactyla as actually being composed of three entities. To account for the variation from the distinct morphology of typical P. didactyla, a new combination P. didactyla var. extenuata (Nyl. ex Vainio) and a new species P. lambinonii are proposed. Both new taxa can produce methyl gyrophorate&gyrophoric acid (often in trace amounts). The significance of the chemical variation among the three taxa is discussed below. Materials and Methods This study is based on nearly 180 specimens from the following herbaria: ALTA, BM (African material only), BP (P. hazslinszkyi only), CAFB, CANL, Goffinet (personal herbarium), Goward (UBC personal herbarium), LG (part only), PMAE and UBC (part only). Almost all collections, depending on the amount of material available were analysed by thin-layer chromatography in solvent G (toluene-ethyl acetate-formic acid: 139:83:8) following Culberson (1972) and White & James (1985).

The Species Peltigera lambinonii Goffinet sp. nov. Peltigerae didactylae affinis a qua imprimis differt rhizinis maxime numerosis, dense ramosis et anastomosantibus, stratum compactum formantibus, et sorediis gyrophoratem methylicum et acidum gyrophoricum producentibus. Typus: Zaïre: Kivu, Top of Mt. Biega, heath with Erica bequaertii and Philippia, 2740 m, 6 January 1972, Lambinon 72/Z/102 (LG—holotypus; herb. Goffinet—isotypus).

The species is named in honour of Prof. Jacques Lambinon (Liège, Belgium) who collected the typus. Thallus medium-sized to 8·0 cm across, tan to light brown when dry; lobes 1·0–1·5 cm broad, flat to concave with upright margins, thin but robust, with maculiform to submarginal soralia, 2–4 mm wide, round to elongate, bluishgrey with brownish margin, eventually confluent; soredia granular, 50–75 ìm in diam.; upper surface smooth, dull, with tomentum appressed near margin and lacking toward centre; lower surface with distinct veins, 0·5 mm wide, pale to dark brown toward the centre; rhizines up to 4 mm long, pale and somewhat fasciculate when young (near margin) but becoming rapidly dark brown, densely branched to fibrillose and anastomosed, forming a dense spongy carpet hiding the lower surface. Cortex paraplectenchymatous, 25– 50 ìm, photobiont layer 50–65 ìm, containing Nostoc, medulla 130–160 ìm. Apothecia up to 4·5 (–6) mm wide, on elongate upright lobes, disc round to elliptical, hazelnut brown, saddle-shaped; hypothecium pale brown; hymenium 70–110 ìm; paraphyses simple; asci clavate to cylindrical 55– 85#11 ìm, containing 8 ascospores; spores acicular, mainly straight, triseptate 35–65#3–4 ìm. Chemistry: Cortex and non-exposed medulla C", K", PD", lacking lichen substances (only trace amounts of unidentified substances); soralia (exposed medulla) patchily C+red and KC+red (quickly disappearing), K", PD", producing the tridepsides methyl gyrophorate, &gyrophoric acid (the

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latter one often in small amounts) and occasionally traces of unknown substances. The presence of gyrophoric acid results in faint C+red and KC+red reactions of the medulla that are best seen when tested on young soralia from which the soredia have been removed. Ecology: Peltigera lambinonii is so far known to grow over soil and humus, among mosses in open sites, in the upper tropical montane forest between 1700 and 2740 m. Distribution: So far, P. lambinonii is known only from East Africa. All collections were made in the mountainous region that links Rwanda, Uganda and Zaïre (Kivu), where it occurs sympatrically with P. didactyla. Remarks: Peltigera lambinonii is easily distinguished from P. didactyla by its abundant, densely branched to mainly fibrillose rhizines that form a thick, dark brown, spongy layer over the paler, hidden, lower surface of the thallus (Fig. 1; Table 1). By contrast, the latter species typically bears a few thread-like to somewhat fibrillose pale rhizines that are mostly restricted to the centre of the thallus. Chemically the two taxa diverge as well: the depsides methyl gyrophorate and &gyrophoric acid appear to be invariably produced in the soralia of P. lambinonii whereas they are typically absent in P. didactyla (Fig. 2, no. 14–17). Dodge (1964) described P. kenyensis based on two collections from Kenya and Uganda. The type material (BM!) lacks vegetative propagules, but is otherwise morphologically identical to typical fertile P. didactyla; the thallus consists of erect apothecia-bearing lobes, the lower surface of which is pale, with few rhizines restricted to the base of the lobes. Chemically the type of P. kenyensis is, however, similar to P. lambinonii in producing the two tridepsides. This observation appears to be best explained by hybridization (see discussion below). On the sole basis of the distinct morphology we have little doubt that P. lambinonii represents a different taxon from P. didactyla. Swinscow & Krog (1988) treated all sorediate and tomentose specimens from East Africa under P. didactyla. Their description of this species broadly overlaps with our concept of P. lambinonii. Examination of herbarium material reveals that both species are actually present there. Further investigations may reveal that P. lambinonii extends eastward and is actually more widespread than reported here. Indeed most characters of P. lambinonii are in agreement with those of P. didactyla sensu Swinscow & Krog (1988) except for their spore size (33–65 versus 70–80 ìm), a difference that can be accounted for either by the small number of spores seen in each study or by the fact that fertile P. didactyla s.str. is included in the material of Swinscow & Krog. Two additional sorediate species occur sympatrically with P. lambinonii and P. didactyla in East Africa: P. ulcerata and P. cichoracea Jatta. Both can be distinguished from the former two taxa by their glabrous and shiny upper cortex. Selected specimens examined: Rwanda: Gishwati forest, 30th km on Gisenyi-Kibuye road, on steep muddy embankment, 2050 m, 1972, Lambinon 72/Rw/500 (H, LG); Rugege forest, at about km 91 on the Butare–Cyangugu road (between Pindura and Uwinka), cool embankment (‘rotten’ metamorphic schist), edge of secondary montane forest, 2400 m, 1974, Lambinon 74/788 (LG, hb. Goffinet).—Uganda: Kigezi: Elephant valley, about 30 miles W of Kabale, near Kabale Gap,

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F. 1. Peltigera lambinonii (Isotypus, Lambinon 72/Z/102). A, Habit (the arrows point on the submarginal soralia). B, Some of the rhizines have been removed (left) in order to show the lower surface. Scales in mm.

2250 m, 1967, Burnet 218 (BM); Toro, among the leopard rock crags above Kilembe, common on mossy turf, 1700 m 1971, Pentecost RE42 (BM); Toro, Ruwenzori, at 5900* level Kilembe Mine, frequent on steep grassy bank, 2000 m, 1971, Pentecost RE123 (BM).—Zaïre: Kivu: Kahuzi Massif, at about km 37 on the Bukavu-Walikale road, in the lower part of the bamboo forest, clearing, next to the road, heath with hair-cap mosses, 2300 m, 1971, Lambinon 71/Z/1111 (LG, hb., Goffinet). Intermediate specimen examined (Peltigera didactyla s.str.–methyl gyrophorate and gyrophoric acid): Kenya: Abedare Mountains, Kinangop, bank of stream in forest, 8890–9000*, April 1938, Chandler 2275 (holotype of P. kenyensis (Dodge; BM).

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T 1. Morphological and chemical characteristics separating taxa within Peltigera didactyla s.lat.

Character

P. didactyla var. didactyla

P. lambinonii

P. didactyla var. extenuata

Thallus

Branched, medium, up to 8 cm across

Mostly unilobate, small, up to 4 cm across

Branched, medium, up to 8 cm across

Veins

Dark brown almost throughout

Pale brown, gradually darkening toward centre

Whitish to pale brown near centre

Rhizines

Densely branched to fibrillose, forming a dense mat, dark brown

Simple to loosely branched, sparse, whitish to pale brown

Mostly abundantly fibrillose, forming a loose mat, whitish to pale brown

Chemistry (tridepsides)

Methyl gyrophorate &gyrophoric acid (in sorediate lobes)

None

Methyl gyrophorate &gyrophoric acid (patchily in whole thallus)

Distribution

East Africa

Cosmopolitan

Circumboreal Europe, North America and Eastern Asia

Peltigera didactyla var. extenuata (Nyl. ex Vainio) Goffinet & Hastings comb. nov. Peltigera canina var. extenuata Nyl. ex Vainio, Meddeland. Soc. Fauna Fl. Fenn. 2: 49 (1878); type: Finland: Tavastia australis, Asikkala, Kaitas 1863, Silén & Norrlin (H!—lectotype). Peltigera canina var. extenuata Nyl. ex Norrlin, Not. Sällsk. Fauna Fl. Fenn. Förh. 11: 178, 1870–nomen nudum.

Thallus medium-sized, up to 8·0 cm broad, pale to greyish brown when dry; lobes up to 1·0–1·5 cm broad and 4·0 cm long, flat or concave, or even wavy, with slightly revolute margins, thin and fragile, with maculiform, rarely widely confluent, soralia 2 mm wide; soredia mainly between 50–75 ìm in diam. (rarely up to 120 ìm); upper surface smooth, typically dull with thick appressed tomentum sometimes becoming loose and detached from cortex, glabrous toward centre; lower surface with veins that are whitish, becoming greyish to brown toward the centre, flat and narrow with large whitish rounded to slightly elongate interstices; rhizines white, densely branched to fibrillose, rarely simple, often forming a dense mat near margin, becoming darker and sparser toward the centre, up to 5 mm long. Cortex paraplectenchymatous 25–55 ìm, photobiont layer 30–65 ìm, containing Nostoc, medulla 100– 150 ìm thick. Apothecia (only one seen) 5 mm wide, on short, elongate, upright lobe, saddle-shaped, with brown disc; hypothecium brown; hymenium hyaline; paraphyses simple; asci clavate 71–80#8–11 ìm, containing eight ascospores, spores acicular mainly straight, tri- to pluricellular (many spores not clearly septate), 41–60#3–4 ìm.

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F. 2. Thin-layer chromatography plate (Merck, silica gel 60F-254, solvent G from White & James 1985; herbarium given for specimens not cited in text). 1 & 18, Pleurosticta acetabulum (Muhr 3134, ALTA) and Platismatia glauca (Goffinet 74, hb. Goffinet); 2, Peltigera didactyla var. extenuata (France, Sérusiaux 10948); 3, P. didactyla var. extenuata (Finland, Goward & Ahti 81-1010); 4, P. didactyla var. didactyla (Finland, Vitikainen 9741, ALTA); 5, P. didactyla var. extenuata (Newfoundland, Ahti 5832); 6, P. didactyla var. didactyla (Newfoundland, Ahti 5832); 7, P. didactyla var. extenuata (Goffinet C90.4.293); 8, P. didactyla var. didactyla (Goffinet C90.4.293); 9, P. lactucifolia (Sérusiaux 10920, LG & hb. Goffinet); 10, Ochrolechia androgyna (Goffinet 47, hb. Goffinet); 11, P. didactyla var. extenuata (Hastings C91.5.20b); 12, P. didactyla var. extenuata (British Columbia; Goward 79-1073); 13, P. didactyla var. didactyla (British Columbia; Goward 79-1068, hb. Goward); 14, P. lambinonii (Lambinon 72/Rw/500, with soredia); 15, P. lambinonii (Lambinon 72/Rw/500, without soredia); 16, P. lambinonii (Lambinon 71/Z/1111, with soredia); 17, P. lambinonii (Lambinon 71/Z/1111, without soredia). Identified lichen substances: references (1 & 18): A, atranorin; N, norstictic acid; S, connorstictic acid; tridepsides: G, gyrophoric acid; M, methyl gyrophorate; T, tenuiorin; triterpenoids hopanes: D, dolichorrhizin; P, peltidactylin; Z, zeorin.

Chemistry: Cortex C", K", PD"; medulla patchy C+red and KC+red (quickly disappearing, and particularly visible near lobe margin), K", PD"; soralia C+red and KC+red (quickly disappearing), K" & PD"; thallus containing the tridepsides methyl gyrophorate and gyrophoric acid (the latter one in small quantities, sometimes not detected) mostly in sorediate lobes. Ecology: Peltigera didactyla var. extenuata occupies a wide-range of ecosystems, but most specimens are from lowland boreal and montane forests. A few collections are from alpine tundra and from the Great Lakes Pinus-Acer-Betula forests. In the boreal forest, var. extenuata occurs in mesic to moist sites, including Picea mariana/Betula-Salix stands, Larix fens, and lakeside Salix swamps. In mountainous areas it ranges from montane Pinus contorta-Picea glauca forests to the alpine tundra. Again, var. extenuata is typically found in more mesic microsites in these higher elevation ecosystems. In most areas var.

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F. 3. World distribution of Peltigera didactyla var. extenuata.

extenuata grows over mosses and particularly epixylic bryophytes. It also occurs rarely on mineral soil or granitic rock. Distribution: At present P. didactyla var. extenuata has been found mainly from North America (Fig. 3). It is widespread across Canada, from westcentral Yukon Territory, southward to Vancouver and eastward to Greenland. At present, a single specimen from northern Colorado is the known farthest southern locality of the variety. Examination of a limited number of European specimens of P. didactyla s. lat. revealed that the var. extenuata is in at least three localities (including the type locality), two from the boreal zone in southern Finland and the other from the montane eastern Pyrenees in France. So far, it is not known from the lowlands of western Europe, where only var. didactyla is known to occur. A similar observation has been made in British Columbia; the var. didactyla is widely distributed, whereas var. extenuata is only found inland and not in coastal localities (T. Goward, pers. comm.). Peltigera didactyla var. extenuata is further known from a single locality in northern China.

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Peltigera didactyla var. extenuata appears to have a circumpolar, borealmontane distribution with some incursions into temperate areas. It is to be expected that as more herbarium specimens of P. didactyla are examined the known range of var. extenuata will increase. Given the widespread occurrence of its habitat type, the latter variety should be found in the Pacific Northwest of the U.S.A., and the Great Lakes and New England states. Although European and Asian distributional data are limited, they correlate well with what is known from North America. We expect P. didactyla var. extenuata in Europe to have a range similar to that described for P. neopolydactyla (Gyelnik) Gyelnik by Vitikainen (1987). In Eastern Asia, further studies may reveal a wide distribution of the taxon in the boreal biome. Remarks: Throughout its range, var. extenuata can be mistaken for the type variety of P. didactyla s.str., as both develop laminal soralia. However, in var. extenuata the veins typically remain pale throughout (occasionally becoming pale brown towards the centre) and the rhizines are typically densely branched to fibrillose and abundant (Fig. 4; Table 1). By contrast, in var. didactyla, the veins generally become dark brown in the centre of the thallus. Its rhizines are simple to scarcely branched, rarely fibrillose except in the centre, where they are often confined, and abundant, otherwise the rhizines are sparse. The lobes of var. extenuata are abundantly branched and overlapping; the older central part does not disintegrate as in var. didactyla. The thalli are often better developed in mesic forested sites, when they grow flat over rotten logs and pleurocarpous mosses. Peltigera didactyla s.str. is rarely found in the latter habitat, and occurs mainly on soil as a pioneer (Wirth 1987). When growing among mosses, the lobes of P. didactyla s.str. often develop an erect habit and become isolated from each other. Furthermore P. didactyla var. extenuata produces methyl gyrophorate and gyrophoric acid (which is rarely undetected) in at least some parts of its thallus, unlike P. didactyla (Culberson 1969, 1970, Fig. 2, nos. 2–8 and 11–13). The presence of gyrophoric acid results in C+red and KC+red reactions of the medulla (best seen on soralia); however, the amount is often limited so that the reactions are faint (these observations are further discussed below). Based on the keys of Gyelnik (1928) and Ozenda & Clauzade (1970), which provide a short description of all synonymized taxa of P. didactyla (as P. spuria; including P. erumpens and P. hazslinszkyi) the specimens here defined as P. didactyla var. extenuata would key out as P. hazslinszkyi. Gyelnik (1928) described P. hazslinszkyi from Central Europe and reported it later also from North America (Gyelnik 1932). We have been unable to obtain the type specimen of this taxon but we have examined material identified as P. hazslinszkyi by Gyelnik (numbers from BP: 3376, 3378, 3380, 3382, 3383, 3392, 3396, 3397, 3401, 3402, 3408, 37358 and 37362). Peltigera hazslinszkyi has ochraceous to centrally dark brown veins, with simple, sparse to numerous rhizines restricted to the inner part of the thallus, whereas P. didactyla var. extenuata develops numerous typically fibrillose rhizines throughout. Some of the specimens of P. hazslinszkyi (3376, 3382, 3396 and 3397) were examined and identified as P. spuria by Vitikainen in 1976. In his key to the European species of Peltigera, Vitikainen (1981) synonymized P. hazslinszkyi with

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F. 4. Peltigera didactyla var. extenuata (Hastings C91.5.20b; PMAE). A, Upper surface. B, Lower surface. Scales in mm.

P. didactyla (as P. spuria) including it in the P. canina group, which is characterized by having ‘no or few (inconstant?) lichen substances’ (Vitikainen 1981). Chromatographic analysis of collections of P. hazslinszkyi cited above, indeed revealed the complete absence of lichen substances. By contrast, methyl gyrophorate and &gyrophoric acid were detected in at least some parts of each thallus of var. extenuata, unlike in any other taxa related to P. canina, ‘which usually lack lichen substances’ (Vitikainen 1985). Thus considering both the morphological and chemical differences, P. hazslinszkyi remains in synonymy with P. didactyla s.str. The type material of P. erumpens (FH!) is also in complete agreement both morphologically and chemically with our concept of P. didactyla s.str. Specimens with broad lobes, abundant,

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fibrillose, pale rhizines, pale veins and producing methyl gyrophorate& gyrophoric acid correspond both morphologically and chemically with the type of P. canina var. extenuata. Considering the correlation between the chemical pattern both with morphological characters and ecological trends, but without distinct geographical differences as both taxa are sympatric, varietal rank appears appropriate to accommodate the new taxon. The thallus of var. extenuata is cup-shaped and unilobate in the early young stages. Identification of such small, immature thalli is more reliable if based on chemical analysis. Indeed, four specimens (Marsh 1857 [ALTA], Brodo 14987 [CANL], Clayden 2697 [CANL], Scotter 4906 [CANL]) with small, strongly concave sorediate thalli, morphologically similar to those found in var. didactyla, were found to produce methyl gyrophorate and gyrophoric acid. We therefore include these specimens in var. extenuata. Because the two tridepsides are produced throughout development, we rejected the hypotheses that var. extenuata represents only a growth stage of P. didactyla s.str. and that the chemicals would be produced only in older thalli of the latter species. When growing together (Goffinet C90.4.293 ALTA; Ahti 5832 (CANL) P. didactyla var. extenuata and P. didactyla s.str. maintain the above morphological (Fig. 5) and chemical (Fig. 2, nos. 5–6 and 7–8, respectively) differences, supporting the hypothesis that the chemical pattern and the distinct morphologies are not induced by, or correlated with, environmental factors. As observed among African material, some specimens from the Northern Hemisphere that are morphologically in agreement with our concept of P. didactyla s.str. were found to produce methyl gyrophorate and gyrophoric acid. These observations appear to be best explained by hybridization (see below). Selected specimens examined: Canada: Alberta: Coleman, 50 miles N of town, 0·5 miles N of summit of Plateau Mountain, 50)13*N, 114)32*W, on ground, 2400 m alt., 1969, Brodo et al. 14987 (CANL); About 90 km south of Red Earth, west of highway 88, 56)20*N, 115)15*W, on hummock (with Peltigera didactyla s.str.), 1990, Goffinet C90.4.293 (PMAE); Waterton Lakes National Park, Lineham Lake trail, coniferous forests one mile from base of trail, 1963, Scotter 4906 (CANL); Fort McMurray area, southeast short of Winefred Lake, 55)28*N, 110)26*W, 602 m, 1991, Hastings C91.5.20b (PMAE, ALTA, CANL & LG). British Columbia: Wells Gray Provincial Park, lower oroboreal zone, Murtle Lake Lagoon trail, 1150 m, 1979, Goward 79–1073 (hb. Goward); Vancouver area, Whytecliff Park, Lowland rain forest of Tsuga, Thuja and Acer, 1987, Marsh 1857 (ALTA). New Brunswick: Labique River, on earth, July 1864, Hay (CANL). Newfoundland: Humber East Distr., 3 miles NW of Little Falls, Upper Humber River, recent burned (with Peltigera didactyla s.str.), 1956, Ahti 5832 (CANL); Labrador, Elisabeth Lake 54)46*N, 66)54*W, rocky shoreline on NE side of lake, 620 m, 1982, Clayden 2697 (CANL). Ontario: Algoma District, Rix Twp. 47)15*N, 84)40*W, Montreal River harbor gorge, 1983, Fishlin 120 (CANL). Quebec: Ottawa District, on earth in woods, Montmorency River, 1905, Macoun (CANL). Saskatchewan: NE of Lytle Lake, 59)28*N, 105)11*W, forest burned, 1973, Wong & Miller 1105 (CANL). Yukon: Dempster Highway, mile 39·9, 64)28*N, 138)15*W, 1270 m, 1973, Ostafichuk 5345 (ALTA).—China: Nei Mongol, Da Hinggan Ling, Mangui, on earth, 52)10*N, 122)20*E, 900 m, 1975, Xi-Ling 3207 (hb. Goffinet).—Finland: Uusimaa: Helsinki, Nordsjö, 60)12*N, 25)11*E, 19 April 1981, Goward & Ahti 81-1010 (hb. Goward).— France: Pyrénées-Orientales: NE slope of the Canigou, Llech valley, below the refuge of the Molina, 1000 m, 1990, Sérusiaux 10948 (LG).—Greenland: Ikâsaulaq, 65)59*N, 37)26*W, 10 m, 1970, Hansen 556 (BM).—U.S.A.: Colorado: Boulder Co., 5 miles W of Nederland, 0·6 miles W of Hessie, 39)57*10+N, 105)36*35+W, along South Fork Middle Boulder Creek, 2895 m, 1973, Shushan sl-6413 ( ALTA). Intermediate specimens examined (a) (Peltigera didactyla var. didactyla–methyl gyrophorate and gyrophoric acid): Canada: Alberta: Morningside campground area, Spruce-larch swamp, 1963, Barclay 1015 (CANL); Waterton Lakes National Park, mile 10, Chief Mountain road, 1966,

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F. 5. Peltigera didactyla var. extenuata (A) and var. didactyla (B) from the same collection (Ahti 5832, CANL). Scales in mm.

Ostafichuk 266-7 (ALTA); Carrot Creek, 1966, Ostafichuk 275-5 (ALTA). Manitoba: Churchill, on burned area in high tundra, ridge E of town, 1950; Thomson 3363 (CANL). Newfoundland: Humber East District, N shore of NE end of Birchy Lake, 1956, Ahti 5853 (CANL); Terra Nova National Park, road cut beside the Trans Canada Hwy, 1967, Ostafichuk 283-3 (ALTA). Ontario: Lake Superior, 1869, Macoun (CANL). Prince Edward Island: West Barkley Beach: 14 miles NW of Charlottetown, 46)26*N, 63)12*W, 1970, Fabieszewski & Grandtner (CANL). (b) (Peltigera didactyla var. extenuata–no chemicals detected): Canada: Alberta: Jasper National Park; Moosehorn Creek trail, 1390 m 1979, Marsh JE9008 (ALTA). Quebec: Lac Ste. Anne, N of Quebec City, c. 800 m, 1959, Shushan 23294 (CANL).—France: Pyrénées-Orientales: Vernet-lesBains, between St-Martin du Canigou and the Col de Segales, 1250 m, 1990, Sérusiaux 10912 (LG).

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Significance and interpretation of tridepsides in P. didactyla s.lat. The two tridepsides methyl gyrophorate and gyrophoric acid, are found in Peltigerae, with laminal soralia growing in rather mesic forested sites. Sorediate specimens from drier open sites lack the tridepsides. Under mesic conditions, decomposition rates can be considered high, when compared to open rather disturbed sites. Guzman et al. (1990) suggested that hopane triterpenoids could provide increased resistance to decomposition. Even though parallel analysis has not been undertaken for the role of depsides, it could be argued that methyl gyrophorate (and maybe gyrophoric acid) has antibacterial or antifungal properties, and would thus protect the thallus from precocious decomposition. These tridepsides would further allow the soredia producing them to withstand fungal and bacterial attack, to develop into a thallus, and thus make possible their establishment in forested localities. By contrast, specimens lacking the tridepsides would be restricted to growing in sites with less stable hydric conditions. This preventive role may be even more significant for the mature sorediate thallus. Methyl gyrophorate could possibly prevent parasitism by lichenicolous fungi that could infest the thalli through its most vulnerable parts, the exposed soralia. If such interpretations, although speculative, reflect actual ‘strategies’, the different chemical trends observed in P. didactyla s.lat. should be viewed as any other specific character that has led to adaptations to different environments. Within the taxa of the P. didactyla complex, some chemical variation has been detected. Discussed here are : (a) the absence or the production in small amounts of gyrophoric acid, and (b) the contradiction between morphology and chemistry for some specimens. In addition to methyl gyrophorate, many specimens contained gyrophoric acid, even though often only in trace amounts. A similar situation exists in P. retifoveata where gyrophoric acid is sometimes detected, but even then only in small quantities. The metabolic link between methyl gyrophorate and its precursor gyrophoric acid in the acetate–polymalonate pathway could account for these observations. Gyrophoric acid may not always accumulate in species that also synthesize methyl gyrophorate and may be fairly continuously processed into the latter. The occasional absence of gyrophoric acid in chromatograms further suggests that the synthesis of the tridepsides is periodic or at least not constant and thus the amounts detected by chemical analysis may vary with the time of collection. Among the material examined some specimens were morphologically in agreement with one taxon but showed the chemical characters of another. The first category includes specimens of P. didactyla s.str. that produced methyl gyrophorate&gyrophoric acid. Such observations were made in the Northern Hemisphere (Ostafichuk 266-7, 275-5 and 283-3 [all ALTA], Ahti 5853 [CANL], Barclay 1015 [CANL], Fabiszewski and Grandtner 27 July 1970 [CANL], Macoun July 1869 [CANL] and Thomson 3363 [CANL]) as well as among African material (Chandler 2275 [BM]). Their morphology was not in agreement with either that of P. didactyla var. extenuata nor that of P. lambinonii, respectively; their veins were pale to dark brown in the centre and the rhizines were sparse and scarcely branched. By contrast, three other specimens

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(Marsh JE9008 [ALTA], Sérusiaux 10912 [LG] and Shushan 23294 [ALTA]) have morphologies that fit our description of P. didactyla var. extenuata, but lack their characteristic lichen substances. These aberrations are best explained by hybridization. Attachment of microconidia to trichogynes has been confirmed in Cladonia furcata (Honegger 1984) and the possibility of their fusion has been invoked to account for observed hybridization in the Cladonia chlorophaea complex (Culberson et al. 1988). As in the case of intermediates found between species in ‘Alectoriae’ (Brodo 1978) and subspecies in the Cladonia gracilis group (Ahti 1980), the aberrations cited here are found in those parts of the range where species are sympatric and, furthermore some of these intermediate specimens are from stands where at least one of the progenitor taxa also occurs. Unfortunately, the absence of chemicals in P. didactyla makes it difficult to assign our specimens to one or more of the hybridization categories proposed by Brodo (1978), i.e. chemical replacement or addition. Observations by Stocker-Wörgötter & Türk (1990) that the thalli of P. didactyla always originated from fused neighboring soredia, and the fact that var. extenuata and var. didactyla can be found growing together make hybridization between adjacent thalli quite plausible. Brodo (1978) suggested that in the absence of sexual recombination, chemical addition in morphological intermediates or specimens retaining only the morphotype of one, could be explained by polyploidization (i.e. diploidization and heterokaryosis). However, we reject this hypothesis for two reasons. First, because it would require, in the absence of morphotypic hybrids (as in our case we have no specimens combining erect fertile lobes with abundant fibrillose rhizines throughout and producing tridepsides), the silencing in the intermediates of all ‘morphological’ genes of one progenitor. Second, considering the alternative solution to silencing, which is invoking the rules of dominance and recessiveness of alleles, the dominance would be reversed in the two series of intermediates found here (chemical alleles of P. didactyla var. extenuata and morphological alleles of P. didactyla s.str. dominant in the first category; chemical alleles of P. didactyla s.str. and morphological alleles of P. didactyla var. extenuata dominant in the second category). Another explanation for intermediates with chemical additions could be thallus fusion (Brodo 1978). Even though ‘the hyphae themselves do not fuse and exchange nuclei, the genotypes of the parents would presumably affect the final morphological and chemical character of the resulting composite’ (Brodo 1978). This appears to be the ‘easiest method of chemical addition’ (Brodo 1978), and could be supported by the demonstration of the required soredia fusion in the asexual reproductive life cycle of P. didactyla s.str. (Stocker-Wörgötter & Türk 1990). However, we dismiss this hypothesis as it would again require opposite effects of genotypic dominance (see above) to explain the characters observed in both series. Introgressive hybridization is the best way to explain the intermediates. It requires sexual reproduction and recombination; the hybrid of the first generation is back-crossed to one progenitor and this cycle repeats itself between the hybrid of the second generation and the same progenitor leading to the incorporation of part of the genome of species A into species B. In our case the process would have to take place as follows: soredia from two taxa (P. didactyla s.str. with either P. didactyla var. extenuata or P. lambinonii) fuse

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together, plasmogamy between different ‘strains’ results in dikaryotic ascogenous hyphae that eventually undergo meiosis during which recombination occurs. Genes accounting for the production of the two depsides specific to P. didactyla var. extenuata or P. lambinonii would be exchanged. The spores resulting from sexual reproduction would be dispersed, associate with a photobiont and develop into a hybrid thallus. This thallus would propagate by means of soredia. Adjacent soredia of the hybrid and P. didactyla s.str. would fuse and undergo lichenization and a new hybridization cycle is made possible. The final result would be specimens with the P. didactyla-like morphology but containing methyl gyrophorate and gyrophoric acid. This hypothesis is supported by the fact that all intermediate specimens of this type (except Ostafichuk 283-3) are fertile, making recombination and subsequent incorporation of genes possible from P. didactyla var. extenuata, via intermediates, into P. didactyla s.str. The second category of intermediates, P. didactyla var. extenuata morphotypes lacking chemicals could be explained in a similar manner. It could represent the alternative product of a recombination affecting only the ‘chemical genes’ in the first generation of hybridization. Introgressive hybridization may not occur as no fruiting bodies were observed on the two intermediate specimens of this type. Given the distinct morphology and chemistry of the large majority of specimens we attribute to P. didactyla var. extenuata (which in addition shows differences in regional distribution) or to P. lambinonii (Table 1), we have no doubt that they represent distinct taxa. Introgressive hybridization appears to be the most parsimonious way to account for intermediates. This study was supported by the Provincial Museum of Alberta and an NSERC operating grant to Dale Vitt. We thank the curators of the cited herbaria for the loan of material, as well as Prof. C. Xi-Ling (IFP) for sending a duplicate of the single Asian collection of var. extenuata. We are particularly grateful to T. Goward (UBC), C. Lafarge-England (ALTA), Dr E. Sérusiaux (LG), and Dr D. Vitt (ALTA) for continuous support and interest in this work and for valuable comments on an earlier version of the manuscript. Special thanks are due to O. Vitikainen (H) for corresponding over critical issues. Constructive criticism was also provided by Dr T. Ahti (H) as well as two anonymous reviewers. Dr W. Culberson kindly clarified some confusion regarding methyl gyrophorate and methylgyrophoric acid. Dr E. Sérusiaux generously provided the Latin diagnosis for P. lambinonii. Miss Marner (OXF) kindly made photographs of the type of P. didactyla available to us. Finally, we thank Drs W. R. Buck and R. C. Harris (NY) as well as Prof. Dr J. Poelt (GZU) for their help in making critical literature available to us. R Ahti, T. (1980) Taxonomic revision of Cladonia gracilis and its allies. Annales Botanici Fennici 17: 195–243. Awasthi, D. D. & Joshi, M. (1982) The lichen genus Peltigera from India and Nepal. Kavaka 10: 47–62. Brodo, I. M. (1978) Changing concepts regarding chemical diversity in lichens. Lichenologist 10: 1–11. Culberson, C. F. (1969) Chemical and Botanical Guide to Lichen Products. University of North Carolina, Chapel Hill. Culberson, C. F. (1970) Supplement to ‘‘Chemical and Botanical Guide to Lichen Products’’. Bryologist 73: 177–377. Culberson, C. F. (1972) Improved conditions and new data for the identification of lichen products by a standardized thin-layer chromatographic method. Journal of Chromatography 72: 113–125.

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