Molecular insights into the lichen genus Alectoria (Parmeliaceae) in North America

Alectoria is a genus of fruticose lichen characterised by the presence of usnic acid and conspicuous raised pseudocyphellae. This genus is particularly diverse and abundant in montane, boreal, and Arctic regions of North America. Because intermediate forms have been reported for several species of Alectoria on the continent, it has been suggested that these species were initially delimited based on the extremes of morphological gradients. Here, we use the results of molecular phylogenetic analyses of two nuclear genes, ITS and Mcm7, with 48 representatives of 9 taxa to examine the delineation of 5 taxa that have been previously shown to be related to, or confused with, A. sarmentosa: A. fallacina, A. imshaugii, A. sarmentosa var. sorediosa, A. sarmentosa subsp. vexillifera, and A. vancouverensis. Alectoria fallacina was found to be well-supported and distantly related to A. sarmentosa. Conversely, the other four taxa were recovered as a single monophyletic group with little internal structure, which did not support the presently defined morphological species. A provisional taxonomic treatment is proposed pending more detailed study at the population level. Alectoria sarmentosa var. sorediosa is recognized at the species level, which necessitates the new combination: A. sorediosa. An updated key to the North American species of Alectoria is also provided.