Molecular and phenotypic study put eastern North American Cetrelia in a global context of biogeography and phylogeny

Species of Cetrelia delimited based on chemical and morphological characters have been largely supported by subsequent phylogenetic analysis of molecular data. While a robust, taxonomically well sampled global phylogeny for Cetrelia exists, geographic sampling to date has focused on Europe and East Asia. Here we use extensive field, herbarium and laboratory study to examine the distributions and identities of the taxa occuring in eastern North America. The presence of three species in the region is confirmed with molecular data (C. chicitae, C. monachorum, C. olivetorum). While a fourth species (C. cetrarioides) also occurs based on phenotypic data; efforts to obtain sequences were unsuccessful. The subpopulations of Cetrelia species in the region have contrasting frequency and distribution patterns relative to disjunct European subpopulations. Quantification of frequency of Cetrelia occurrence compared to an index of habitat quality revealed that all species have a strong affinity to high quality habitats, reflecting broader connection between lichen species richness and disturbance found in numerous previous studies. The trends detected in Cetrelia are unlikely restricted to this genus and we suggest that large-scale detailed quantitative studies in local-scale occurrence over time are needed to address significant gaps in knowledge to advance lichen conservation.