Introduction
Phyllopeltula Kalb, a genus in the Lichinomycetes, comprises two species. The type species, Phyllopeltula corticola (Büdel & R. Sant.) Kalb, was originally described from a single locality in Kenya as Peltula corticola Büdel & R. Sant. (in Büdel Reference Büdel1987). It has since been reported from the Seychelles(Seaward & Aptroot Reference Seaward and Aptroot2006), Aldabra (Seaward & Aptroot Reference Seaward and Aptroot2009), Namibia, Yemen, California (Büdel et al. Reference Büdel, Rauhut, Schulz, Nash, Gries and Bungartz2007) and Taiwan, where it is rather common (Aptroot & Sparrius Reference Aptroot and Sparrius2003). The other species, P. steppae Kalb, is known only from two collections from South America (Kalb Reference Kalb2001).
Both Phyllopeltula species occur on exposed, dusty trees, except in Taiwan, where P. corticola was mostly found on dry rock. During our collecting trips we found the type species mostly in the lowlands (below 40 m alt. except in Taiwan, where it was once found at 700 m alt.), generally in coastal areas, but in countries as far apart as Hawaii, Puerto Rico, Taiwan, Thailand and the Philippines. Together with the known records from Africa, this shows that Phyllopeltula corticola is pantropical. When found, it is usually quite abundant and covers most of a tree trunk (or rock face) and may quite often be found even in cities on roadside trees, such as in Honolulu and in San Juan. The species is probably generally overlooked or mistaken, for Phaeophyscia species, which have a somewhat similar colour and lobe configuration, but which differ by the presence of rhizines and green algae instead of cyanobacteria.
In one locality in the Philippines, part of the material bears a multitude of peculiar, simple or branched dorsiventral lobes with an internal structure similar to normal Phyllopeltula corticola, but differing markedly by soredia being formed all over the lower surface of the lobes rather than in lip-shaped soralia and by the marked papillose cells of the lower cortex, but especially by the presence of green algae instead of cyanobacteria. Virtually all specimens of Phyllopeltula corticola on one tree bear one or more (up to many dozens per specimen) of such lobes. In total, many thousands of such folioles have been collected and many more have been left undisturbed. Significantly, these lobes are found only on specimens of Phyllopeltula corticola, not directly on the bark or on other lichens.
Material and Methods
Identification and descriptive work was carried out in Soest using an Olympus SZX7 stereomicroscope and an Olympus BX50 compound microscope with interference contrast, connected to a Nikon Coolpix digital camera and in Wangen using a Wild A. M3 stereomicroscope, a PZO Biolar compound microscope with interference contrast, a Canon EOS 40D camera with MP-E 65 mm and a Mic HM 560 cryotome. The materials are preserved in ABL, BM, F, and hb. Schumm.
Selected specimens studied. Phyllopeltula corticola. Hawaii: Oahu: Honolulu, Waikiki beach, 1989, A. & M. Aptroot 26258 (ABL).—Puerto Rico: San Juan, Punta Piedrita, May 1989, A. & M. Aptroot 24901 (ABL); Ponce, Reserva forestal de Guanica, May 1989, A. & M. Aptroot 25815 (ABL).—Seychelles: Bird Islands, 4 iv 2001, J. Gerlach (ABL, BM).—Aldabra: Bassin Flamant, 1973, R. J. Hnatiuk (BM).—Taiwan: Koahsiung County: Kaohsiung, Tsaishan, 2001, Aptroot 53033 (F). Pingtung County: Kenting, near Frog Rock, 2001, Aptroot 53340 (F). Taichung County: 30 km E of Taichung, 5 km W of Kukwan, 2001, Aptroot 53530 (F). Taipei County: 25 km N of Taipei, near Sanji, 2001, Aptroot 53600 (F).—Thailand: Kanchanaburi, 2002, F. Schumm 9527 (ABL, hb. Schumm).—Philippines: Negros: Negros Oriental, Dumaguete, 2000, F. Schumm 7349 & Schwarz (ABL, hb. Schumm).
Phyllopeltula steppae. Venezuela: Lara, Torres, 35 km E of Barquisimeto, 1989, K. & A. Kalb, distributed in Kalb, Lichenes Neotropici no. 469 sub Physcia crispa (ABL—isotype).
Description of the green algal parts
Lobes containing green algae originating from thalli of Phyllopeltula corticola containing cyanobacteria, are usually situated on the soredia. Lobes (Fig. 1A & C) grey, dorsiventrally applanate, simple to repeatedly dichotomously to flabellately branched, 0·2–0·4 mm wide, up to 2 mm long, usually slightly curved downward, on the lower surface and on the tips with granular soredia of c. 20–40 μm diam. Soredia (fig 1E) originating on lower surface mostly green, those originating on lobe tips grey, cells with papillae. Upper cortex dull, smooth, paraplectenchymatous, not deviating from cyanobacteria-containing Phyllopeltula corticola (Fig. 1D). Medulla (Fig. 1B) with green algae with cells c. 5 μm diam. Lower cortex dull, paraplectenchymatous, cells c. 5 μm diam., strongly papillose (Fig. 1E). Papillae on lower cortex and on soredia hemispherical, c. 1 μm wide and high, with up to 30 papillae per cell.
Phyllopeltula corticola with chimeras (Schumm 7349 & Schwarz). A & C, habitus; B, section through chimera; D, section through cyanobacteria-containing thallus; E, soredia with green algae and papillose cells. Scales: A = 1 mm; B = 20 μm; C = 2 mm; D = 100 μm; E = 10 μm.
Discussion
Given the similarity in upper cortex structure between Phyllopeltula corticola and the folioles, and the strict association of the two elements, we have no doubt that the folioles represent another manifestation of the same lichen. Such photosymbiodemes, where cyanobacterium-containing species bear folioles with green algae, have been called chimeras and have so far been reported from only a few genera in the Peltigerales in the Lecanoromycetes (James & Henssen Reference James, Henssen, Brown, Hawksworth and Bailey1976; Armaleo & Clerc Reference Armaleo and Clerc1991). In the inverse cases, where green algae-containing lichens bear structures with cyanobacteria, the structures (which can be foliole-shaped or not) are called cephalodia or sometimes also chimeras in a wider sense. They are more common than chimeras with green algae and known from various lichen orders (James & Henssen Reference James, Henssen, Brown, Hawksworth and Bailey1976), though so far equally unknown from the Lichinomycetes. The genus Euopsis, which is only doubtfully classified in the Lichinales, is the only known possible member of this order that can contain cyanobacteria and algae simultaneously. However, its thallus is crustose and the sections containing algae are not morphologically recognizeable. As Phyllopeltula belongs to the Peltulaceae (Kalb Reference Kalb2001), which is classified in the Lichinales in the Lichinomycetes, a lichen group unrelated to the Peltigerales or even the Lecanoromycetes, this implies the first observation of chimeras in a totally unrelated group. The classification of at least the type species of Phyllopeltula in the Peltulaceae has been confirmed with molecular methods (Rauhut Reference Rauhut2006); it even clusters within the genus Peltula.
Strongly papillose cells are rare in lichenized ascomycetes (and unknown in non-lichenized ascomycetes). They occur only in the Verrucariaceae genus Agonimia Zahblr. (including the synonymous genera Agonimiella H. Harada and Flakea O. Erikss., see Aptroot et al. Reference Aptroot, Diederich, Sérusiaux and Sipman1997) and in the only doubtfully different genus Psoroglaena Müll. Arg. (see Lücking Reference Lücking2008). Virtually indistinguishable but markedly larger structures occur in the monospecific lichenized basidiomycete Acantholichen P. M. Jørg. (Jørgensen Reference Jørgensen1998).
Harrie Sipman is warmly thanked for a discussion of the species and a valued second opinion on the specimen with chimeras.
