Molecular phylogenetic studies reveal an undescribed species within the North American concept of Melanelixia glabra (Parmeliaceae)

We employ a molecular phylogenetic approach using nuclear ITS and mitochondrial SSU rDNA gene regions to test the general efficacy of species boundaries in the morphological species Melanelixia glabra. 35 new sequences are generated for this study. Our results provide evidence that M. glabra is polyphyletic, indicating that using only morphological criteria to define species boundaries in this group of lichenised fungi underestimates actual species-level diversity. These analyses also demonstrate that the geographically distant population of the M. glabra complex in North America is the sister group of two Indian species (M. glabroides and M. villosella) and exhibits considerable molecular divergence from the European and Turkish specimens (M. glabra s. str). Additionally, some minor morphological differences support the isolation of the American clade. Such results strongly suggest that this population of M. glabra is a new phylogenetic (morphological+phylogenetic) taxon that is described here as a new species (Melanelixia californica). Our approach using two independent genes appears to be a rigorous method to critically examine species boundaries originally based on traditional morphological approaches in this group of lichenised fungi. Our study shows that the use of morphology, molecular data and geography provide a robust approach to delimitation of phylogenetic species.