During a revision of type material of tropical lichenized fungi housed in the herbarium of the Naturhistorisches Museum Wien (W), the first author came across the original material of Phyllobathelium nudum, described by Zahlbruckner (Reference Zahlbruckner1928) from the island of Java in Indonesia. Phyllobathelium is a small genus of chiefly foliicolous, more rarely corticolous, lichens in the family Strigulaceae in the class Dothideomycetes (Santesson Reference Santesson1952; Harris Reference Harris1995; Lücking et al. Reference Lücking, Aptroot and Thor1997; Roux & Sérusiaux Reference Roux and Sérusiaux2004; Lücking Reference Lücking2008; Nelsen et al. Reference Nelsen, Lücking, Grube, Mbatchou, Muggia, Rivas-Plata and Lumbsch2009, Reference Nelsen, Lücking, Mbatchou, Andrew, Spielmann and Lumbsch2011; Lumbsch & Huhndorf Reference Lumbsch and Huhndorf2010; Lücking & Nelsen Reference Lücking and Nelsen2013). It is characterized by a shiny, grey-green thallus with metallic glance and perithecia usually covered by the thallus, and with a powdery, black mass of crystals between the thallus and excipulum.
The species described as Phyllobathelium nudum was considered non-lichenized by Santesson (Reference Santesson1952: 288) and therefore not further treated in his monograph on foliicolous lichens. However, revision of the type material revealed that it is in fact lichenized with a trentepohlioid photobiont, but that it does not belong in Phyllobathelium, since the perithecia feature a compact, exposed, black involucrellum lacking a crystalline powder, a fact already recognized by Zahlbruckner (Reference Zahlbruckner1928), and are instead similar to those of Strigula. The combination of Strigula-like perithecia and muriform ascospores places this species in the genus Phyllocratera Sérus. & Aptroot (Aptroot et al. Reference Aptroot, Diederich, Sérusiaux and Sipman1997), which thus far includes only the type species, P. papuana Sérus. & Aptroot, known from Papua New Guinea.
Phyllobathelium nudum agrees with Phyllocratera papuana in all aspects, except that the perithecia are smaller (0·4–0·8 mm vs. 0·8–1·2 mm), but the ascospores are longer (75–90×13–17 µm vs. 55–75×13–18 µm). These inverted size differences suggest Phyllobathelium nudum represents a second species in Phyllocratera, which is supported by its different distribution, as far as can be judged from the only available specimen. Therefore, we propose the following new combination:
Phyllocratera nuda (Zahlbr.) Lücking & Sérus. comb. nov.
MycoBank No.: MB 804335
Phyllobathelium nudum Zahlbr., Ann. Crypt. Exot. 1: 115 (1928); type: Indonesia (Java), Mt. Gede, 21 January 1924, Schiffner 3464 (W—holotype!).
(Fig. 1)
A, holotype specimen of Phyllobathelium nudum (W); B, Phyllocratera nuda, thallus and perithecia (holotype in W); C, P. papuana, thallus and perithecia (isotype in F). Scales: B & C = 1 mm. In colour online.
Notes. Phyllocratera nuda shares with P. papuana the general thallus and perithecial morphology and anatomy, and a full description of the latter species is given in Aptroot et al. (Reference Aptroot, Diederich, Sérusiaux and Sipman1997). The thallus is superficial and easily detached from the leaf surface. The photobiont was left unidentified by Aptroot et al. (Reference Aptroot, Diederich, Sérusiaux and Sipman1997), but is identical to that found in Strigula phyllogena and related species (Lücking Reference Lücking2008) in the development of cylindrical but strongly curved cells with interspaces, forming a characteristic network; in Phyllocratera, the photobiont is concentrated in lines and patches, giving the thallus surface a variegated or marmorate appearance. The perithecial involucrellum is completely carbonized and very thick and basally spreading, similar to most species of Strigula; the excipulum is more or less hyaline and rather thin and prosoplectenchymatous in the upper and basal portions but thicker and distinctly paraplectenchymatous along the outer basal edges. The hamathecium is very dense (see fig. 90 in Aptroot et al. Reference Aptroot, Diederich, Sérusiaux and Sipman1997: 134). The muriform ascospores are very similar to those of Phyllobathelium species (see fig. 91 in Aptroot et al. Reference Aptroot, Diederich, Sérusiaux and Sipman1997: 135). Phyllocratera papuana and P. nuda share all of the above features, and the only differences are morphometrical, with P. nuda having smaller perithecia (about half the size of P. papuana on average) but larger ascospores (about 25–30% larger on average). This inverted size difference, together with the occurrence in Indonesia (Sundaland floristic province), whereas P. papuana is known from Papua New Guinea (New Guinea and Bismarck Archipelago floristic province), supports the distinction of these two species and makes Phyllocratera a genus characteristic of the Malesia biogeographic region.
Except for the large, muriform ascospores, which are similar to those of Phyllobathelium, species of Phyllocratera closely resemble those of the Strigula phyllogena group; this differs from other foliicolous species of Strigula in the supracuticular growth and very uniform perithecial anatomy, and it was previously considered a separate genus, Phylloporis (Santesson Reference Santesson1952; Vězda Reference Vězda1984; Harris Reference Harris1995; Lücking Reference Lücking2008). The very broad concept of Strigula currently applied (Harris Reference Harris1995; McCarthy Reference McCarthy1997, Reference McCarthy2009; Roux & Sérusiaux Reference Roux and Sérusiaux2004; Lücking & Nelsen Reference Lücking and Nelsen2013) would suggest including Phyllocratera within Strigula, because muriform ascospores occur in non-foliicolous species currently accepted in the latter. However, the morphological and anatomical uniformity within, and distinctiveness between, species recognized in Strigula s. str. (S. elegans group), the S. phyllogena group, and Phyllocratera, compared to non-foliicolous species, suggests that this group contains several distinct genus-level lineages, and molecular data are needed to address this problem. We therefore continue to recognize Phyllocratera as a separate genus. The marmorate disposition of the photobiont and the partially paraplectenchymatous excipulum support this view.
This study was made possible by two grants provided by the United States National Science Foundation (NSF) to The Field Museum: “Neotropical Epiphytic Microlichens” (DEB 0715660; PI Lücking) and “ATM—Assembling a taxonomic monograph: The lichen family Graphidaceae” (DEB 1025861; PI Lumbsch, Co-PI Lücking). The head of the cryptogam collection at W, Anton Igersheim, as well as Othmar Breuss, are warmly thanked for their assistance in examining the material.
