Usnea lichens: GBS Raw Sequence Reads. Usnea

Neuropogonoid species in the lichen-forming fungal genus Usnea exhibit great morphological variation that can be misleading for taxonomical descriptions. We specifically focused on the species delimitation of two closely-related predominantly Antarctic species differing in the reproductive mode and representing a so-called species pair: the asexual U. antarctica and the sexual U. aurantiacoatra. Previous studies reveled contradicting results: while multi-locus studies based on DNA sequence data suggested they might be conspecific, microsatellite data suggested they represent distinct lineages. By using RADseq, we generated thousands of homologous markers to build a robust phylogeny of the two species. Furthermore, we successfully implemented these data in fine-scale population genomic analyses such as DAPC and fineRADstructure. Both Usnea species are readily delimited in phylogenetic inferences and therefore the hypothesis that both species are conspecific was rejected. Also, population genomic analyses strongly confirmed separated genomes, and additionally showed different levels of co-ancestry and substructure within each species. Lower co-ancestry in the asexual U. antarctica than in the sexual U. aurantiacoatra may be derived from a wider distributional range of the former species. Our results demonstrate the ability of this RADseq method to trace population dynamics in a deeper Usnea sampling in future analyses.