<scp>DNA</scp> sequencing of Linnaeus's <i>Ulva compressa</i> , <i>U. intestinalis</i> , and <i>U. linza</i> (Ulvaceae, Chlorophyta) and other <i>Ulva</i> type specimens

The names published by Linnaeus in Species Plantarum represent the foundation of modern plant taxonomy. Despite their systematic value, very few of Linnaeus's original type specimens have been analyzed using current DNA sequencing technologies. Here, we performed high-throughput sequencing on Linnean and other type specimens of Ulva, a genus of ecological and commercial importance. Chloroplast and mitochondrial genomes were assembled for Linnaeus's U. compressa, U. intestinalis, U. lanceolata, and U. linza as well as Kützing's Phycoseris smaragdina type specimens. Phylogenetic analyses of these data showed that the names U. compressa and U. intestinalis were correctly applied, but U. linza and U. lanceolata were misapplied. Ulva linza is the earliest available name for the European species currently called U. pseudocurvata. The correct name for the globally distributed species previously known as U. "linza" is Ulva smaragdina (Kützing) comb. nov. The names Ulva lanceolata, U. crispata, and Phycoseris olivacea do not represent distinct species, instead being heterotypic synonyms of U. compressa, and P. planifolia is a heterotypic synonym of U. intestinalis. These results demonstrate that genetic characterization of type material can unequivocally resolve longstanding taxonomic debates over scientific names.