|TAXONOMY OF THE CALICIALES|
We have proposed the following classification of the crustaceous lichenized Caliciales in Norway
|The delimitation of Chaenotheca versus Cybebe Article from The Lichenologist: Tibell (2001)|
|The delimitation of Chaenotheca versus Sclerophora|
Description of the Caliciaceae Fee.
Thallus crustaceous. Phycobiont Trebouxia. Apothecia stalked, sessile, or immersed. Mazaedium black. Excipulum well developed, thick or thin. Pruina absent or present. Asci cylindrical or clavate; formed singly, croziers present. Spores one-septate, ellipsoid, dark brown with a surface of irregular cracks, spirally arranged ridges, or almost smooth.
Thallus endosubstratal or granular, green to grey. Phycobiont Trebouxia. Apothecia black or rarely dark brown, stalked. Excipulum well developed. Mazaedium black. Pruina on the apothecium brown, yellow, white, or absent. Asci cylindrical or clavate. Spores one-septate, ellipsoid, dark brown with a surface of spirally arranged ridges or more or less irregular cracks.
Thallus episubstratal, verrucose, yellow, grey or greenish grey. Phycobiont Trebouxia. Apothecia black, sessile or immersed. Excipulum thin, or thick at the base. Mazaedium black. Pruina white on excipular margin, or absent. Asci cylindrical or broadly clavate. Spores one-septate, dark brown with a surface of irregular cracks or almost smooth.
THELOMMA Massal. emend Tibell
Only one species belonging to the genus Thelomma has been found in Norway, Thelomma ocellatum (Korber) Tibell Thallus verrucose, grey. Black isidia occur in globular areas. Medulla I+ dark blue. Phycobiont Trebouxia, Chlorococcales. Apothecia immersed, very rare in Norway. Mazaedium black. Excipulum thick at the base. Pruina absent. Asci cylindrical. Spores ellipsoid, 22-28 x 12-15 pm, one-septate with an almost smooth surface. Secondary substances usually absent, but some specimens contained either atranorin or norstictic acid in the thallus. Tibell (1976b) reported usnic acid, epanorin and rhizocarpic acid. T. ocellatum is lignicolous on worked timber in exposed habitats (fence posts, wooden roofs etc.). It is an ornithocoprophilous species.
Remarks. This is the first report of a fertile r. ocellatum in Fennoscandia. There are two fertile specimens collected in Norway: Sogn & Fjordane, Aurland, 1968, 0vstedal; and Oppland, Vaga, Veomoan, Mattsson & Middelborg 553. Our collection is from an old wooden fence. The thallus is well developed, but isidia are less frequent than usual. Apothecia are rare, only three apothecia were found in this collection. The other collection contains only one apothecium. Fertile specimens are more common in Central Europe (Tibell 1976b).
Description of the Coniocybaceae Reichenb.
Thallus crustaceous. Phycobionts Dictyochloropsis, Stichococcus, Trebouxia, or Trentepohlia. Apothecia stalked. Mazaedium brown or pale brown. Excipulum well developed or poorly developed, collar absent or present. Pruina usually present. Asci cylindrical or of irregular shape; catenulate or formed singly, croziers present or absent. Spores non-septate, globose or ellipsoid, brown or pale brown with a reticulate or cracked surface.
CHAENOTHECA (Th.Fr.) Th.Fr.
Chaenotheca is a heterogeneous genus. Thallus endosubstratal or episubstratal, granular, farinaceous, verrucose or squamulose. Thalline colour green, yellow or grey. Phycobiont Dictyochloropsis or Trebouxia (Chlorococcales), Stichococcus or Trentepohlia (Tibell 1980b). Apothecia are stalked, 0.5-3.0 mm tall.black or dark brown. Excipulum well or poorly developed, without collar. Mazaedium medium or pale brown. Pruina on the apothecium yellow, yellowish green, white or reddish brown; or absent. Asci cylindrical or irregular; catenulate or formed singly, croziers present or absent. Spores globose or ellipsoid, nonseptate, brown. Spore surface with irregular cracks.The identified secondary substances occurring in Chaenotheca are vulpinic acid, pulvinic acid, pulvinic dilactone, atranorin, baeomycesic acid, squamatic acid, and anthraquinoid pigments.
Thallus endosubstratal. Phycobiont Trentepohlia. Apothecia brown or pale, stalked, 0.4-1.5 mm tall.. The hyphae of the stalk are pale brown, and periclinally arranged. Excipulum poorly or well developed, with or without a collar. Mazaedium pale brown. Pruina yellow, reddish-brown or violet, K- or K+ violet. Asci cylindrical. They are formed singly, and croziers are present in the formation of the ascus. Spores globose, non-septate, pale, with a reticulate surface. Anthraquinoid pigments occur in the apothecia.
Description of the Microcaliciaceae Tibell
Parasites or parasymbionts on Caliciales species, parasites on algae, or saprophytes on bark or lignum. Apothecia stalked or sessile. Mazaedium greenish black. Excipulum well developed. Pruina absent. Asci cylindrical; catenulate, croziers absent. Spores 1-3-7-septate, ellipsoid, green with a surface of spirally arranged ridges.
Thallus endosubstratal, saprophytic on lignum, parasymbiontic, or parasitic on algae or lichens. Apothecia black, sessile or stalked. Excipulum well developed. Mazaedium greenish black or dark brown, sclerotized hyphae present or absent. Pruina absent. The mazaedium contains a probably intracellular, greenish, K+ brown pigment. Asci cylindrical, formed in chains without croziers (Schmidt 1970a). Spores ellipsoid, greenish, 1-3(-7)-septate with a surface of spirally arranged ridges. Pycnidia present or absent.
DELIMITATION OF CHAENOTHECA (Th.Fr.) Th.Fr. VERSUS CYBEBE Tibell AND SCLEROPHORA Chevall.
Tibell (1984) has revised the taxonomy of the Caliciales. He placed the species belonging to Coniocybe in Chaenotheca and in Sclerophora and established the monotypic genus Cybebe. He also gave a description of the families.
Description of Cybebe
Cybebe is a monotypic genus containing Cybebe gracilenta (Ach.) Tibell, syn. Chaenotheca gracilenta (Ach.) Mattsson & Middelborg, syn. Coniocybe gracilenta (Ach.) Ach. The thallus is episubstratal, granular. The phycobiont is Stichococcus. The apothecia are stalked, 2.4-3.5 mm tall. The hyphae of the stalk are brown, and periclinally arranged. The excipulum is poorly developed without collar. The mazaedium is greyish brown. The asci are cylindrical, catenulate, and croziers are absent in the formation of ascus. The spores are globose and pale brown, with a surface of irregular cracks. We have observed four unidentified secondary substances.
The delimitation of Chaenotheca versus Cybebe
According to the descriptions given above, Cybebe differs from Chaenotheca mainly in having an ascus formation without croziers (Nadvornik 1941, Schmidt 1970a). Tibell (1984) also emphasizes the small and pale spores and the lack of secondary substances. We wish to stress the similarities between Chaenotheca and Cybebe in ascocarp structure, excipulum structure, spore structure and the catenulate asci. Catenulate asci are rare among lichenized fungi, in the Caliciales being known from Chaenotheca, Cybebe and Microcalicium only. Microcalicium differs from the two other genera in several morphological characters. The presence of catenulate asci in Chaenotheca can thus be regarded as a result of parallel evolution. However, in our opinion the formation of catenulate asci in Chaenotheca and Cybebe has evolved once, and we regard Chaenotheca and Cybebe as a monophyletic group. The absence of croziers in Cybebe is probably a secondary feature that has been established after the formation of catenulate asci. In our opinion the catenulate asci, the small and slightly cracked spores, the poorly developed excipulum and the lack of vulpinic acid link Cybebe to Chaenotheca subgenus Chaenotheca.
In a chemical investigation of Cybebe we have observed four unidentified secondary substances. It is our opinion that the unidentified substances should not be used in the seperation of Cybebe from the chemically heterogeneous Chaenotheca. In SEM, spores of Cybebe show the pattern as Chaenotheca spp. (Tibell 1980b). The surface consists of cracks and irregular areas.
Thus we do not accept Cybebe at generic level, but regard it as synonymous with Chaenotheca.
The delimitation of Chaenotheca versus Sclerophora
According to the descriptions given above, Sclerophora differs from Chaenotheca in having an endosubstratal thallus, Trentepohlia as phycobiont, and an excipulum structure like a collar surrounding the stalk. The spores in Sclerophora have a reticulate surface, and anthraquinoid pigments always occur in the apothecia; while Chaenotheca spores have a cracked surface and vulpinic acid or anthraquinoid pigments occur in the apothecia. An examination of Chaenotheca spp., however, shows that some species have an endosubstratal thallus (C. xyloxena), Trentepohlia as phycobiont (C. hispidula), and anthraquinoid pigments in the apothecia (G. ferruginea, C. gracillima). An examination of Sclerophora spp. shows that S. peronella lacks a collar, and has an excipular structure similar to that of several Chaenotheca species, e.g. C. stemonea. The main difference between the two genera is the ontogeny of the spore walls. According to Tibell (1984) Chaenotheca spores have an "ornamentation formed by rupturing of the primary wall". Sclerophora spores have an "ornamentation formed by intraplasma-lemmatic irregularities of the outer surface of the spore wall~. We have compared SEM photographs of spores in two Sclerophora species. They are clearly distinct from Chaenotheca spores (Tibell 1980b). According to the treatment above, the ontogeny of the spore walls is the only feature which clearly separates Sclerophora and Chaenotheca. We find this insufficient for placing Sclerophora in the monotypic family Sclerophoraceae Tibell, and we therefore place Sclerophora with Chaenotheca in the Coniocybaceae.
Leif Tibell: Cybebe gracilenta in an ITS/5.8S rDNA based phylogeny belongs to Chaenotheca (Coniocybaceae, lichenized Ascomycetes). From The Lichenologist Vol. 33 (6), 2001, p. 519 – 525.
The analysis presented in Fig. 1 shows Cybebe gracilenta forming a well-supported monophyletic group with Chaenotheca gracillima (j=94) clearly inside Chaenotheca. In an earlier analysis (Tibell 2001), Chaenotheca gracillima did not join any of five well supported clades in Chaenotheca. A description of Chaenotheca gracillima may be found in Tibell (1999) and, like Cybebe gracilenta, it is included in the Swedish Red List, and is classified as ‘Care demanding’. It has a wider distribution than Cybebe gracilenta, also occurring in the Southern Hemisphere: in Australasia (Tibell 1987) and South America (Tibell 1998). In the present analysis Chaenotheca gracillima and Cybebe gracilenta are sister species. They are also morphologically similar in having rather flexuous stalk, and occur in similar habitates. They are both associated with the photobiont Stichococcus. Asci are also formed in chains in Chaenotheca gracillima, at least in some populations, but the asci have distinctive and persisting hooks. The spore wall is well pigmented in Chaenotheca gracillima. The secondary chemistry, however, seems to be quite different. While triterpenoids and unidentified compounds are produced by Cybebe gracilenta, and possibly contributing to a grayish or white pruina on the apothecia, a dark reddish brown pigment is produced by Chaenotheca gracillima. This pigment occurs on the capitula and upper parts of the stalks and dissolves in K, and soon a precipitate of violet-red plate- to feather-like crystals is formed (as seen under the microscope). Interestingly this, or a similar unidentified pigment, also yielding a precipitate of violet-red plate to feather-like crystals, is also known from Calicium, for example C. salicinum Pers.
The second analysis (Fig. 2) shows the two specimens of Cybebe gracilenta forming a strongly supported group (j=100). The specimens of Chaenotheca gracillima fall into two different clades. One clade contains one specimen from New Zealand and one from India and is strongly supported (j=96), while the other, containing specimens from Argentina, Chile, New Zealand and Sweden, has only moderate support (j=80). Thus, in this second analysis there is little support for Chaenotheca gracillima, as circumscribed here, to be monophyletic. Furthermore, there is a clear geographical pattern in the ITS sequence evolution of C. gracillima. The Southern Hemisphere specimens are generally more closely related. In the present alignment there is only a difference in one base pair between the South American specimens and those from New Zealand and Sweden are 14-15 bp and 19-20 bp, respectively. There is, however, an interesting difference between this clade and that containing the specimens from India (T116) and New Zealand (T005), which form a strongly supported clade (j=96) but which differs from the other clade in 28-35 bp. These specimens may represent a cryptic species or perhaps a different allele in C. gracillima.
The present analysis of the ITS-5.8S-ITS2 rDNA shows that, in addition to the five clades previously recognized (Tibell 2001), Cybebe gracilenta and Chaenotheca gracillima form a well-supported group in Chaenotheca and thus supports the earlier suggestion of Middelborg & Mattsson (1987) that Cybebe should be included in Chaenotheca as Chaenotheca gracilenta (Ach.) Middelb. & Mattsson.