Gowardia zebrina sp. nov., a new species in a little-known genus of arctic-alpine lichens (Parmeliaceae)

Gowardia zebrina differs from other species in the genus by its combined subpendent habit, uniformly capillary branches, predominantly isotomic branching, pale-and-dark banding of the terminal branches, and epiphytic ecology. Morphological examination of North American herbarium specimens filed under A. nigricans suggests the existence of several additional undescribed species of Gowardia. A brief overview of morphological diversity in these species is given, shedding new light on the question of whether Gowardia should be subsumed under Alectoria, as some have suggested, or is more appropriately recognized as a distinct genus.

Methods

Phylogenetic study was based on sequences of nuclear ribosomal ITS regions from 29 specimens, including four specimens from the genus Alectoria and 24 specimens from Gowardia. Bryocaulon divergens (Ach.) Kärnefelt belongs to the Alectorioid clade sensu Divakar et al. (2015) together with Alectoria and Gowardia and was used as an outgroup. Seven new ITS sequences were generated for this study.

The remaining sequence data were obtained from the NCBI GenBank (www.ncbi.nlm.nih.gov/genbank/), including all available ITS sequences of Gowardia. The ITS sequences were aligned with MUSCLE v.3.8.31 (Edgar 2004) using EMBL-EBI’s freely available web service (ebi.ac.uk/Tools/msa/ muscle/). Phylogenetic relationships were inferred using maximum likelihood (ML) as optimality criteria.

The ML analysis was performed in RAxML v.8.1.15 (Stamatikis 2104) located at CSC – IT Center for Science (csc.fi/english). We divided the data set into three partitions (ITS1 region, 5,8S gene, ITS2 region) and used a GTRGAMMA model because GTR is the only substitution model implemented in RAxML. Nodal support was estimated with 1000 bootstrap replicates using the rapid bootstrap algorithm.