The Chemistry and Systematics of Some Species of the Cladonia cariosa Group in North America

Abstract

Cladonia polycarpia, an endemic of the coastal plain of the southeastern United States, consistently produces atranorin and norstictic and stictic acids. Records of this species from western North America are referable to C. cariosa and C. symphycarpa. Cladonia polycarpoides is abundant and widely distributed in the East but absent from most of the range of C. polycarpia. It produces norstictic acid and lacks stictic acid and atranorin. Cladonia subcariosa, a rare species producing atranorin and norstictic acid, is known from Cuba and a few localities in the Atlantic coastal plain. Morphologically, chemically, and taxonomically Cladonia is the best known of the large genera of lichens. In spite of the intensity with which the genus has been studied, numerous species groups within it remain poorly understood-the result of inadequate collecting in critical regions, analytic procedures too insensitive to assess the chemical variation, or insufficient study of morphological variation, or a combination of all of these factors. The Cladonia cariosa complex is one of these problem groups. The present study grew out of my interest in the relationship between Cladonia polycarpoides and C. polycarpia, two common, almost allopatric species of the eastern United States. Most of the effort of the present research went to the systematics of these two species, and data on other members of the group are included for comparative purposes only. Some of the species are well differentiated morphologically, such as C. apodocarpa and C. capitata. The rest of the species resemble each other greatly although subtle morphological differences, some of which might better be called mere tendencies, seem to accompany most of the major chemical types. Chemistry, however, shows an impressive variation. Chemically the C. cariosa group is quite distinct (Table 1). With the exception of C. cariosa itself, every species contains at least one depsidone of the p-orcinol series. While the p-orcinol depsidone fumarprotocetraric acid is widely distributed in many Cladoniae, other p-orcinol depsidones are rare outside of the C. cariosa group (Culberson, 1969). Psoromic acid is known in only a few species in addition to C. brevis. Norstictic acid, a constituent of four members of the C. cariosa group, is known additionally in Cladonia only in the single species C. acuminata. In the entire genus the only stictic acid-producing species is C. polycarpia. There are, moreover, no /orcinol depsidones in Cladonia which are not represented in the C. cariosa group. 1 Assistance from grant GB-8359 from the National Science Foundation is acknowledged with thanks. I also thank Dr. Teuvo Ahti and Dr. John W. Thomson for criticism of the manuscript and Dr. Ahti and Dr. Mason E. Hale, Jr., for the loan of specimens. 2 Department of Botany, Duke University, Durham, North Carolina 27706. This content downloaded from 207.46.13.124 on Wed, 22 Jun 2016 05:19:57 UTC All use subject to http://about.jstor.org/terms 378 THE BRYOLOGIST [Volume 72 TABLE 1. The major secondary natural products in the North American species of the Cladonia cariosa group. The substances are: atr = atranorin; nor = norstictic acid; sti stictic acid; fum = fumarprotocetraric acid; pso = psoromic acid.