The Ramalina farinacea Complex in North America: Chemical, Ecological and Morphological Variation

Abstract

Ramalina farinacea (L.) Ach. is most abundant along the coastal regions of North America from approximately 30-600N latitude. All of the five European chemical races are present in the New World in addition to unreported combinations of diagnostic acids. An analysis of morphological variation in chemical lines showed them to be indistinguishable. There is evidence of a latitudinal gradient in the abundance of the chemical races, and different substrate preferences are exhibited in different regions of their distributions. Lichen chemistry has played a major role in the interpretation of morphological variation and species definition in many groups. Detailed investigations of ecological and/or morphological variations in lichen species have been studied in many fertile groups, of which the Cetraria islandica (Kristinsson, 1969) and Ramalina siliquosa complexes (Culberson, 1967; Sheard 1978a,b) are good examples. In these studies the variability of different chemical lines was extensively examined throughout a wide range of the distribution of the species, and evolutionary and taxonomic models for these groups were proposed. In another study the ecological and evolutionary relationships of a complex polyphyletic group of foliose lichens, the Parmelia perforata species series composed of both sexual morphology and derivative sorediate species, was investigated in its Old and New World ranges (Culberson, 1973). However, no group of sorediate species has been dealt with in a similar manner. In view of our current knowledge of the disparate nature of sexual and asexual reproductive strategies (Poelt, 1970; Bowler & Rundel, 1975), it is important to investigate the ecological amplitudes in geographically diverse populations to evaluate the evolutionary distance between chemical races of asexually reproducing groups. The Ramalina farinacea complex is a chemically diverse series of closely related sorediate races with a broad distribution throughout the temperate regions of the Northern Hemisphere. The ancestral esorediate morphologies of all of the chemical lines are not known and may have reached extinction. This group is a widespread and ecologically important sorediate complex, and has received much study in Europe. The chemical ecology of R. farinacea in Europe has served as a basis for the construction of a taxonomy for the group comprising five principal taxa (varieties and/or species 1 We thank Irwin M. Brodo, R. H. Harris and W. L. Culberson for comments on previous drafts of this manuscript. I. M. Brodo kindly allowed the use of unpublished data, and C. F. Culberson provided standards and determined several unknown compounds. Financial support was provided by the National Science Foundation (Grants GB-40509; DKB75-19848), a National Defense Education Act Title IV Fellowship and a National Research Council of Canada Postdoctoral Fellowship through the Museum of Natural Sciences, National Museums of Canada. 2 Department of Ecology and Evolutionary Biology, University of California, Irvine, CA 92717. 0007-2745/78/386-403$2.05/0 This content downloaded from 157.55.39.35 on Thu, 01 Sep 2016 05:33:30 UTC All use subject to http://about.jstor.org/terms 1978] BOWLER & RUNDEL: THE RAMALINA FARINACEA COMPLEX 387 according to different workers). These were distinguished primarily by chemical characteristics supported by morphological trends and substrate preferences (Culberson, 1966; Hawksworth, 1968; Krog & James, 1977). Little study has been made of the R. farinacea complex in North America. Several chemical races are known from the Pacific Coast, New England and the Great Lakes region in North America, but it has not been clear if the morphological and ecological characteristics upon which the speciation of the series in Europe was interpreted are consistent. Substantiation of judgments of the evolutionary distance between chemical races should emerge more clearly from extensive studies in North America. It is the purpose of this research to investigate morphological variations, distributions and ecology of the chemical races and implications of these characteristics in the evolutionary relationships within the R. farinacea complex in North America.