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Ramalina thrausta (Ach.) Nyl., Ramalina roesleri (Hochst. Ex Schaerer) Hue, and Ramalina dilacerata (Hoffm.) Hoffm. are three common North American species that have not been placed in a phylogeny and are sympatric in their distribution leading to uncertainty about monophyly. Species characters include secondary metabolites (polyketides) in Ramalina that may be both hereditary and influenced by environmental conditions, but little is known about the function of polyketide synthase (PKS) genes. The main goal of this study was to examine the monophyly among some of the more common species in northern North America and secondarily to compare potential PKS gene function with the phylogeny. Nucleotide sequences of two genes, the internal transcribed spacer 1 of ribosomal DNA and the mitochondrial small subunit, were used to infer a phylogeny. Gene function was inferred from three PKS genes by the ratio of nonsynonymous to synonymous substitutions (dN:dS) ratios. Although seven species of Ramalina are highly supported in monophyletic clades, two other species form clusters with low support: Ramalina americana Hale is paraphyletic, and Ramalina pollinaria (Westr.) Ach. is polyphyletic. Three PKS genes were inferred to be functional but were not present in all samples. Functional PKS genes could enable adaptation to new habitats and facilitate species diversification.

Ramalina sinensis is a widespread lichen in the Northern Hemisphere with sparse local populations, and its potential to adapt to changing environmental conditions is unknown. The objectives of this study were to determine whether geographical distance reflects fungal phylogenetic patterns, and to infer algal identity and its pattern of geographical distribution. Twenty-three samples of R. sinensis were collected from three geographical regions in Manitoba. The internal transcribed spacer of ribosomal DNA (ITS rDNA) was sequenced from each of the algal and fungal partners, and phylogenetic analyses were performed. Algal haplotypes were estimated and placed on a map of the geographical regions. Although the fungal partner showed no geographical segregation within Manitoba, the divergence of three samples added to the phylogeny from GenBank suggested that a pattern may be evident if broader geographical distances were examined. The photobiont sequence was determined to be most similar to that of Trebouxia impressa and T. potteri, two widely distributed algal species. The algal partner showed no geographical structure with sequence polymorphism or haplotype analyses. The abundance of sexual reproduction might explain widespread occurrence and the absence of geographical segregation of the fungus. This study suggests that the diversity in each of the symbionts of R. sinensis should not be a limiting factor for adaptation.

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