Pyxine Fr., Syst. Orb. Veget.

Mongkolsuk, Pachara, Meesim, Sanya, Poengsungnoen, Vasun & Kalb, Klaus, 2012, The lichen family Physciaceae in Thailand-I. The genus Pyxine, Phytotaxa 59 (1), pp. 32-54 : 33-35

Pyxine Fr., Syst. Orb. Veget. 1: 267 (1825).

Type:— P. sorediata (Ach.) Mont. in Ramón de la Sagra, Hist. phys., polit. natur. Cuba, Bot. Plant. Cellul. 2: 188 (1842) .

Thallus foliose, continuous, lobate, loosely to tightly adnate, 1–20 cm wide. Lobes irregular to radiating, discrete or contiguous, 0.2–2.0 (–5.0) mm wide, eciliate; apices rounded to truncate. Upper surface white, grey-white to bluish grey, lead-grey or yellow-grey, plane to convex, or concave towards the periphery, ± reticulately ridged, glossy or dull, usually pruinose; soredia, isidia and polysidiangia (= dactyls; Fig. 4E ; for a detailed description of these structures see Swinscow & Krog, 1978: 162 and Kalb, 1987: 17 and Fig. 8) present or absent; pseudocyphellae usually present, of irregular linear form, usually white or pale grey, red in Pyxine coccifera . In distribution they may be laminal or marginal or both. In some cases, e.g. in P. coccifera and P. subcinerea , marginal pseudocyphellae develop into soralia. Upper cortex paraplectenchymatous, formed by vertically orientated hyphae. Medulla uniformly white or upper part pigmented yellow, orange, salmon-pink or scarlet, rarely uniformly pigmented. Lower surface usually brown-black or black, often paler towards the periphery, rarely grey-white or pale brown, rhizinate; rhizines simple or furcate; lower cortex prosoplectenchymatous, formed of horizontally orientated hyphae. Ascomata apothecial, laminal, rounded, sessile or subpedicellate, with a distinct internal stipe that is white, brown or red; disc black, rarely pruinose; thalline exciple prominent or reflexed, either distinct and persistent ( physciaeformis - type), or distinct in young apothecia, but becoming excluded, so that the apothecia appear lecideine ( cocoës - type), or absent and all apothecia appearing lecideine ( obscurascens - type); proper exciple present and persistent, ± blackened. Epihymenium bluish black, K+ purple. Hymenium colourless. Hypothecium brown to dark brown. Paraphyses septate, simple or with short branches near the apices; apices generally capitate, brown-black, K+ purple. Asci of Biatora - type, clavate, with a well-developed amyloid tholus with a paler subconical axial mass and an ocular chamber, 8-spored. Ascospores brown, 1–3-septate, thick-walled, ellipsoidal, mischoblastiomorphic [usually Dirinaria - type, rarely Physcia - type (Mayrhofer 1982)], 10–23 × 4–9 μm. Conidiomata pycnidial, laminal, immersed; conidiophores of type VI (sensu Vobis, 1980), pleurogenous. Conidia bacilliform, 3–4 × 0.8–1.2 μm.

Pyxine is a mainly pantropical to subtropical genus, with several species extending into temperate or oceanic regions; currently considered to comprise ca. 70 species, 20 of which occur in Thailand. These lichens grow on bark, wood, mosses or rocks.

Notes:—The genus most closely related to Pyxine is Dirinaria ( Jungbluth & Marcelli 2012) . The latter lacks rhizines and the species are fastened to the substrate by hapters. Furthermore, the epihymenium is K- and does not turn purple when K is added. Characteristic substances in Pyxine are atranorin or lichexanthone in the cortex and especially terpenes in the medulla, in Dirinaria however divaricatic or sekikaic acid are found in the medulla together with a few terpenes. Also some species of Physcia may resemble a Pyxine , but these are easily separated by the K- epithecium and a colourless hypothecium. Many Physcia species contain zeorin, but never lichexanthone, testacein or norstictic acid like numerous Pyxine species. In some keys ( Zahlbruckner 1926, Aptroot 1988a ['1987']), the separation of Pyxine from Dirinaria is made on the basis of lecideine versus lecanorine apothecia, although Stirton (1898) previously described both types as well as an intermediate type from Pyxine . For the same reason, this character cannot be used to discriminate Pyxine from Physcia .

Key to the species of Pyxine in Thailand ( P. berteriana and P. farinosa are included for convenience)

1. Thallus UV+ yellow, lichexanthone present ...................................................................................................... 2.

- Thallus UV-, atranorin present .......................................................................................................................... 7.

2. (1.) Thallus sorediate ................................................................................................................................................ 3.

- Thallus without vegetative propagules............................................................................................................... 4.

3. Medulla uniformly white........................................................................................................................ P. cocoës

- Medulla—at least the upper part— lemon-yellow to yellow ........................................................... P. subcinerea

4. (2.) Medulla uniformly white ................................................................................................................... P. petricola

- Medulla – at least the upper part – pale yellow, lemon yellow or orange.......................................................... 5.

5. Lobes 0.5–1.5 mm wide; upper medulla (pale) yellow, lower medulla white; apothecia of cocoës - type ........... .......................................................................................................................................................... P.berteriana

- Lobes 0.3–1.0 mm wide; medulla pale yellow, lemon yellow or orange; apothecia of obscurascens - type ..... 6.

6. Lobes 0.5–0.8 mm wide, medulla uniformly pale yellow or lemon yellow ................................. P. australiensis

- Lobes 0.3–1.0 mm wide, medulla orange in upper part, lower medulla white .................................... P. cognata

7. (1.) Vegetative propagules absent ............................................................................................................................ 8.

- Polysidiangia (dactyls), soralia or isidia present ( Fig. 3A, E ; Fig. 4A, B, E ) ................................................. 11.

8. Medulla K- or K+ slightly violet in patches, norstictic acid absent .................................................................. 9.

- Medulla K+ yellow → red, norstictic acid present .......................................................................................... 10.

9. Medulla uniformly creamy to sulfur yellow .................................................................................. P. meissnerina

- Medulla uniformly white.................................................................................................................... P. schmidtii

10. Terpene profile identical to that of P. retirugella , P. copelandii and cylindrica ( Fig. 1 , 2 ) .............. P. philippina

- Terpene profile identical to that of P.fallax and P. boonpragobiana ( Fig. 1 , 2 )................................ P. profallax

11. (7.) True cylindrical isidia present ( Fig. 3E )........................................................................................................... 12.

- True cylindrical isidia absent, soralia or polysidiangia present ..................................................................... 13.

12. Medulla K-, norstictic acid absent ........................................................................................ P. pseudokeralensis

- Medulla K+ yellow → red, norstictic acid present .......................................................................... P. cylindrica

13. (11.) True soralia present, polysidiangia absent ...................................................................................................... 14.

- True soralia absent, polysidiangia present which may simulate soralia when abraded ( Fig. 4E ) ................... 19.

14. Pseudocyphellae and soredia scarlet .................................................................................................. P. coccifera

- Pseudocyphellae and soredia ± pale cream to whitish .................................................................................... 15.

15. Medulla uniformly white...................................................................................................................... P. asiatica

- Medulla coloured, at least in the upper part.................................................................................................... 16.

16. Medulla uniformly creamy to sulfur yellow, soralia marginal ( Fig. 4B ), pruina in extended patches near the apices of the lobes ( Fig. 4D ) ......................................................................................................... P. meissnerina

- Medulla not uniformly coloured, lower part white, soralia laminal ( Fig. 4A ) or laminal and marginal, pruina absent or punctiform near the apices of the lobes ( Fig. 4C ) ............................................................................ 17.

17. Soralia starting from marginal fissures, atranorin often lacking or present in traces only ............... P. sorediata

- Soralia starting from laminal warts, atranorin always present as a major substance ...................................... 18.

18. Soralia sessile, upper medulla beige, creamy or pale orange............................................................. P. daedalea

- Soralia distinctly elevated, upper medulla orange to orange-red ......................................................... P. farinosa

19. (13.) Medulla coloured creamy yellow, yellow-orange or yellow-brown, at least the upper part............................ 20.

- Medulla uniformly white ................................................................................................................................. 21.

20. A characteristic purple terpene spot with Rf-values 59, 61, 49 on TLC plates in solvents A, B' and C .............. .................................................................................................................................................... P. subcoralligera

- A characteristic brown terpene spot with Rf-values 54, 45, 47 on TLC plates in solvents A, B' and C .............. ......................................................................................................................................................... P. coralligera

21. Medulla K-, norstictic acid absent ......................................................................................... P. dactyloschmidtii

- Medulla K+ yellow → red, norstictic acid present ......................................................................................... 22.

22. Terpene profile identical to that of P. copelandii , P. philippina and P. cylindrica , a characteristic purple terpene spot with Rf-values 58, 34, 36 on TLC plates in solvents A, B' and C ( Fig. 1 , 2 ) .......................... P. retirugella

- Terpene profile identical to that of P. fallax and P. profallax , no purple terpene spots, but a characteristic brown major terpene spot with Rf-values 63, 52, 52 on TLC plates in solvents A, B' and C ( Fig. 1 , 2 ) ........................ ............................................................................................................................................... P. boonpragobiana

Figures

FIGURE 1. TLC profiles of some Pyxine species in solvent A. Run 1: Relative standard Rf-values (downwards) 75 (atranorin), 70 (usnic acid), 59 (sordidone), 42 (unknown), 40 (norstictic acid), 34 (notatic acid), 30 (unknown), 27 (stictic acid), 12 (physodic acid), 10 (salazinic acid), 6 (unknown), 3 (protocetraric acid); run 2: P.retirugella, run 3: P. fallax; run 4: P. boonpragobiana; run 5: P. subcoralligera; run 6: P. coralligera; run 7: P.schmidtii; run 8: P. dactyloschmidtii; run 9: P. keralensis; run 10: P. pseudokeralensis.

FIGURE 2. TLC profiles of some Pyxine species in solvent C. Run 1: Relative standard Rf-values (downwards) in solvent C: 79 (atranorin), 71 (usnic acid), 49 (unknown), 45 (4-O-methylhypoprotocetraric acid) 38 (notatic acid), 30 (norstictic acid), 23 (physodic acid), 18 (stictic acid); 8 (unknown); 5 (protocetraric acid); 4 (salazinic acid), 2 (unknown); run 2: P. retirugella, run 3: P. fallax; run 4: P. boonpragobiana; run 5: P. subcoralligera; run 6: P. coralligera; run 7: P. schmidtii; run 8: P. dactyloschmidtii; run 9: P. keralensis; run 10: P. pseudokeralensis.

FIGURE 3. A. Pyxine boonpragobiana (hb. K. Kalb 36928), thallus with polysidiangia; Scale: 3 mm. B. Pyxine dactyloschmidtii (holotype), thallus with polysidiangia; Scale: 3 mm. C. Pyxine pseudoceralensis (holotype), thallus with isidia; Scale 2 mm. D. Pyxine subcoralligera (holotype), thallus with polysidiangia; Scale 3 mm. E. Pyxine cylindrica (hb. K. Kalb 36836), thallus with marginal and partly laminal isidia; Scale 2 mm. F. Pyxine cognata (hb. K. Kalb 12344), thallus with obscurascens-type apothecia and patchy priuna; Scale 3 mm.

FIGURE 4. A. Pyxine fallax (hb. K. Kalb 33866), thallus with laminal orbicular soralia; Scale 1 mm. B. Pyxine subcinerea (hb. K. Kalb 21749), thallus with marginal soralia; Scale 3 mm. C. Pyxine sorediata (hb. K. Kalb 35553), lobe tips with punctiform pruina and marginal pseudocyphellae; Scale 1 mm. D. Pyxine meissnerina (lectotype), lobe tips with patchy pruina; Scale 2 mm. E. Pyxine coralligera (hb. K. Kalb 36599) polysidiangia; Scale 1 mm. F. Pyxine retirugella (hb. K. Kalb 30629) lobe tips with pseudocyphellae; Scale 1 mm.