Expanded taxon sampling disentangles evolutionary relationships and reveals a new family in Peltigerales (Lecanoromycetidae, Ascomycota)

Lichens that incorporate cyanobacterial symbionts (cyanolichens) are an ecologically key group of species used as biomonitors at all latitudes. Cyanolichen evolution is however based on intense studies of few keystone species and the bulk of species diversity, especially of small species in cold climates, has yet to be accounted for in phylogenetic studies. We assembled an expanded data set including members of all nine currently accepted Peltigeralean families as well as hitherto undersampled representatives of small, radially symmetrical, placodioid cyanolichen genera from the Northern and Southern Hemispheres. Bayesian and maximum likelihood consensus trees from our multilocus analyses (nuSSU, nuLSU and mtSSU) recovered the genera Koerberia, Vestergrenopsis and Steinera as a new, fully supported, family-level clade within the Peltigerales. This clade is further supported by a posteriori morphological analysis and we describe it here as the new family Koerberiaceae. The recently described and physiognomically similar genus Steineropsis, by contrast, is recovered as sister to Protopannaria in the Pannariaceae (Collematineae). Previous analyses have recovered strong monophyletic groups around Pannariaceae, Lobariaceae and Peltigeraceae. We discuss in detail the phylogenetic relationships of all these taxa, provide a pan-Peltigeralean overview of phenotypic characteristics and illustrate all major ascus apical structures. Our topology provides strong backbone support for the sister relationship of Peltigerineae to Collematineae as well as for most currently recognized families of the Peltigerales. The following new combinations are made: Steinera symptychia (Tuck.) T. Sprib. & Muggia, and Vestergrenopsis sonomensis (Tuck.) T. Sprib. & Muggia.