| The Cladonia chlorophaea complex of lichen-forming, ascomycetous fungi represents a central problem in the systematics of lichens. This group, characterized by small cups developing from a mat of squamules, includes a large number of chemotypes. These chemotypes, which are morphologically indistinguishable but differ in secondary-product chemistries, have been recognized either as separate species or members of a single species. In the present study, I have examined four chemotypes of the C. chlorophaea complex that are sympatric in the Southern Appalachians, two of which interbreed. Individuals from natural populations were scored for variation in chemotype, morphology and ribosomal DNA (rDNA) genotype. The chemotypes of 1,485 individuals were determined by standard thin-layer chromatographic methods and the morphologies of 914 individuals were classified as qualitative characters. The rDNA genotypes of 120 individuals were identified as restriction-fragment patterns by two techniques: (1) Southern hybridization of genomic DNA with a homologous nuclear rDNA probe and (2) polymerase chain reaction (PCR) amplification of the 3;Natural populations of this complex from the Southern Appalachians contained individuals that differed in chemotype, morphology and rDNA genotype. At least 20 rDNA genotypes were found in a single population; multiple genotypes occurred within each chemotype and a few genotypes were shared by chemotypes. A progeny analysis, comparing the rDNA genotypes of maternal individuals and their sporeling offspring, showed that some rDNA genotypes are polymorphisms within interbreeding groups. These rDNA genotypes differed in the length of the 3... |
