The Genera Cetrariastrum and Concamerella (Parmeliaceae): A Chemosystematic Synopsis

The pantropical genus Cetrariastrum (= Everniastrum Hale) has its center of diversity in the highlands of northern South America and of Mesoamerica but it also occurs in the mountains of southern Africa and southern Asia. It was probably differentiated in Gondwanaland, but tropical-island disjunctions reveal the efficacy of long-distance dispersal for a few of its commonest species. Two species earlier thought to belong to it but endemic to a xeric region of southeastern South America differ in having exceptionally thick upper cortices riddled with special algae-containing chambers, an apparent adaptation to their harsh habitat. They form the new genus Concamerella. Both Cetrariastrum and Concamerella have secondary-product chemistries characterized by f-orcinol depsidones and fatty acids. Excluding the fatty acids, 17 known compounds are reported from the former and seven from the latter, based upon the thin-layer chromatographic analyses of415 specimens. Three species earlier included in Everniastrum are assigned to Parmotrema or Hypotrachyna. Cetrariastrum consists of 23 species; 22 of these comprise four that are new, six that are validations of older names and 12 that are new combinations. The narrow-lobed lichens related to Parmelia cirrhata, the first of these species to have been described, are familiar to all lichenologists who have visited the New World tropics, the place of their greatest diversity. They were first recognized as a distinct assemblage by Hue (1898), who created Parmelia sect. Evernilformes for them. Hale (1976) recently placed them in a genus of their own, Everniastrum. In studying these species we find that in reality two genera differing strikingly in cortical morphology are involved, Everniastrum sensu stricto and the new ditypic genus Concamerella. The present study characterizes these genera and refines the species-level taxonomy by morphological and chemical analysis. Although the generic epithet Everniastrum has been available for only about four years, a considerable body of information has been published and stored under that name. When we found that Everniastrum is a nomen nudum, we intended to validate that name in Latin in the present study and our manuscript submitted to THE BRYOLOGIST in early February, 1981, made that provision. Almost simultaneously a regional study by Sipman (1980) ap007-2745/81/273-314$4.25/0 274 BRYOLOGIST [Volume 84 peared in which a new genus, Cetrariastrum, was segregated from Everniastrum. Sipman's genus is taxonomically unacceptable for many reasons explained below, but Cetrariastrum becomes the correct name for Everniastrum. MATERIALS AND METHODS This study was based primarily upon collections in DUKE and us, the herbaria with the best representation of materials from the parts of the Neotropics in which Cetrariastrum is most abundant. Other specimens were borrowed from LD, LIL, MVM, PC, TAMU, TUR, UPS, w and the private herbarium of Hector S. Osorio. In all, 651 herbarium specimens were studied, 415 (64%) being analyzed by thin-layer chromatography (TLC). For each species we cite at least one specimen from every country from which material was seen, but for Mexico we cite at least one specimen per state. In listing specimens with multiple collectors only the first collector's name is used. All the major phenolic products encountered were easily identified by the TLC method described elsewhere (C. F. Culberson & Ammann 1979), but some fatty acids were less well resolved and included compounds for which critical controls were not available. Fatty-acid Group 1 (Table 1) includes at least two distinct chemistries with either protolichesterinic acid or alloprotolichesterinic acid as the major component. It is possible that some specimens have neither of these compounds but have instead homologous acids with TLC characteristics very similar to those of protolichesterinic and alloprotolichesterinic acids. At the beginning of the present study we used Cetraria islandica (L.) Ach. (France, Culberson 11721-DUKE) and Pycnothelia papillaria (Ehrh.) Duf. (South Carolina, Culberson 10816-DUKE) as sources of controls for lichesterinic and protolichesterinic acids. When purified samples of these and related fatty acids were kindly furnished by Siegfried Huneck, we confirmed that our P. papillaria indeed contained lichesterinic and protolichesterinic acids but found that our C. islandica included some thalli producing lichesterinic acid and protolichesterinic acid, like P. papillaria, and others producing lichesterinic and alloprotolichesterinic acids as the major substances. Two-dimensional TLC (Solvent B x Solvent C) of the alloprotolichesterinic acid-producing chemotype of C. islandica also showed a trace of protolichesterinic acid and an unidentified fatty acid with TLC characteristics resembling those of roccellaric acid. Some species of Cetrariastrum showed TLC spots similar to those of the alloprotolichesterinic acid-containing chemotype of Cetraria islandica. Others resembled P. papillaria with regard to fatty acids. TLC analyses of aliphatic substances in Cetrariastrum are difficult and ours were performed over a long period of time, making most plate-to-plate comparisons impossible. Without a detailed chemical study of these compounds, which would exceed the scope of the present research, we can only classify these compounds as belonging to the protolichesterinic acid group. Fatty-acid Group 2, found only in Concamerella, is characterized by two acids with Rf classes A6, B3, C5 and A2, B4, C5 respectively. The identification of 3-orcinol depsidones, a class of compounds particularly abundant in Cetrariastrum, has recently been discussed in detail (C. F. Culberson et al. 1981). The successful detection of trace compounds usually depends upon the relative proportions of other constituents also present. For example, consalazinic acid probably occurs in most if not all specimens of Cetrariastrum that contain salazinic acid; but, in some mixtures, especially those with smaller proportions of salazinic acid, consalazinic acid may not be detected. Similarly, connorstictic acid was usually identified in specimens that contained relatively high amounts of norstictic acid but not in those with only traces of this compound. Also, the orcinol depside lecanoric acid could usually be detected in trace amounts in specimens with abundant gyrophoric acid. MORPHOLOGY AND CHEMISTRY The morphological features of Cetrariastrum and of Concamerella, which is here segregated from Everniastrum Hale, are typically parmeliaceous save in two respects, the upper cortex of Concamerella and the rhizines of the Americanum Group of Cetrarias-