The delimitation of Antarctic and bipolar species of neuropogonoid Usnea (Ascomycota, Lecanorales): a cohesion approach of species recognition for the Usnea perpusilla complex

Species of the Neuropogon group in the lichen genus Usnea have their centre of distribution in polar regions of the Southern Hemisphere. Their morphological and chemical variability is poorly understood and several asexual taxa with uncertain relationships to fertile taxa occur in the group. The species concept is controversial. A phylogenetic analysis revealed three related complexes of mainly asexual lineages arranged around three fertile Usnea species: U. aurantiaco-atra, U. trachycarpa and U. perpusilla. In this study a dataset of 80 specimens was used to resolve species circumscriptions in the U. perpusilla complex. We used a phylogenetic and a haplotype network approach based on three gene fragments (ITS, IGS and RPB1) to detect distinct lineages. To support the hypothesis that these lineages represent different species, we tested for correlation of morphological and chemical characters with hierarchical nested haplotype groups, employing statistical tests of contingency tables and analysis of variance (ANOVA). This cohesion species recognition method detected three fertile U. perpusilla lineages. We could also delimit an undescribed fertile species with yellow apothecia and a new asexual species from the High Andes. Interestingly, there is an additional bipolar species, U. lambii, which was formerly confused with U. sphacelata. The fact that U. lambii shows a geographically disjunct distribution pattern, but the genetic distances among specimens are low, points to recent long-distance dispersal.