Evolution and reproduction modes in the Roccella galapagoensis aggregate (Roccellaceae, Arthoniales)

The “species pair” concept obscures both intra‐ and interspecific relationships and should be abandoned, evolutionarily and taxonomically. Based on our molecular phylogenetic work on the genus Roccella we are able to show for the first time that sexually and vegetatively dispersed entities in an anticipated “species pair” ( Roccella galapagoensis/R. lirellina ) actually form several distinct monophyletic genotypes, here interpreted as species in which sexual reproduction has been repeatedly evolved. The species accepted here are based on a phylogenetic hypothesis supported by data from the ITS rDNA region and an unidentified locus possibly related to calmodulin. Altogether 89 sequences from both loci were newly produced and used in phylogenetic analyses. The Roccella galapagoensis aggregate was resolved as monophyletic. The sister group includes Roccella decipiens (sexual) and R. gracilis (asexual). Based on the present data it is equally parsimonious to suggest a sorediate or a fertile ancestor to the Roccella galapagoensis aggregate. The ancestor must have arrived in the Galapagos Islands through long distance dispersal and have included the ability to reproduce both sexually with ascospores and asexually with soredia. Taxonomy, nomenclature and phylogeny are provided for five American Roccella species in the Roccella galapagoensis aggregate with geographical focus on the Galapagos Islands. One species is obligatory sexual, one is obligatory asexual and three species are facultative sexual/asexual. Roccella albida Tehler is newly described. Roccella canariensis is united with R. tinctoria .