The lichen genus Candelariella in western North America

The lichen genus Candelariella comprises crustose to small squamulose members of the family Candelariaceae. The genus currently includes c. 50 species world-wide but few studies have treated the taxonomy within this group. In the present thesis the taxonomy of the genus in western North America is treated. Nine new species are proposed and in total twenty-one species are recognized from the region. Three species are characterized by apothecia that lack a thalline margin. Two of these are described as new, C. lichenicola and C. biatorina. Candelariella lichenicola, a lichenicolous species growing on Candelina submexicana, is the only known species in the genus that is not lichenized. Six species, including the type species of the genus, C. vitellina, are characterized by having polyspored asci. One new polyspored species is described, Candelariella borealis. The remaining species have lecanorine apothecia and 8-spored asci. In this group six species are described as new; C. aggregata, C. californica, C. complanata, C. corallizoides, C. deppeanae and C. immarginata. Candelariella kansuensis is reported from North America for the first time. Candelariella deflexa is treated as a synonym to C. aurella and C. terrigena is treated as a synonym to C. citrina. Candelariella citrina, C. rosulans, C. terrigena and C. vitellina are lectotypified. Detailed morphological and anatomical descriptions are provided for all species and their distribution in western North America is mapped. All species are depicted in a color photograph. I addition to the taxonomic studies the phylogeny of the family Candelariaceae was investigated using nuclear ITS DNA sequence data. Twenty-three species of Candelariella, 6 species of Candelaria and 2 species of Candelina and Placomaronea respectively, was sequenced. The phylogenetic analysis were performed using maximum parsimony and Bayesian MCMC inference. The resulting trees from both methods were poorly resolved and strong support were only found for terminal clades. The results indicate that polyspored asci have evolved a limited number of times within the family and appear within four clades. One of these clades comprises the core group of Candelariella including the type species C. vitellina. Placomaronea and Candelina both form strongly supported monophyletic clades, but the two genera are not distinctly separated morphologically from Candelariella and their positions in the trees are uncertain. The genus Candelaria is probably polyphyletic and should possibly be restricted to comprise only polyspored species with a lower cortex