New, resurrected and redefined species of Mastocarpus (Phyllophoraceae, Rhodophyta) from the northeast Pacific

Recent molecular phylogenetic investigations of the red algal genus Mastocarpus from the northeast Pacific resolved numerous cryptic species. Although species were clearly defined through genetic analyses, the correct names to apply to the species remained unclear due to both morphological variability within species and morphological similarity between species. To determine the appropriate name for each entity, we analyzed DNA from type material of taxa previously ascribed to Mastocarpus. In combination with this analysis, an updated phylogeny based on a broad range of geographical and morphological collections is presented that includes data from nuclear (ribosomal internal transcribed spacers [ITS]), chloroplast (rbcL) and mitochondrial [cytochrome oxidase I (COI)] genomes. By analyzing partial ITS region sequences of type specimens, we are able to match currently accepted names (Mastocarpus papillatus, M. pacificus and M. jardinii) to modern collections. We resurrect the following specific epithets and propose the new combinations Mastocarpus cristatus, Mastocarpus latissimus and Mastocarpus agardhii, and we create new species for which we were unable to verify an existing name: Mastocarpus alaskensis, Mastocarpus intermedius, Mastocarpus vancouveriensis, Mastocarpus californianus and Mastocarpus rigidus. The species formerly included in M. papillatus are now identified as Mastocarpus alaskensis, M. papillatus, Mastocarpus intermedius, Mastocarpus cristatus, Mastocarpus vancouveriensis and Mastocarpus latissimus. The name M. jardinii applies to a species thus far collected only from Moss Beach in San Mateo County and the Monterey Peninsula, both in California. Specimens other than the type previously assigned to M. jardinii are now separated into three species: Mastocarpus rigidus, Mastocarpus californianus and Mastocarpus agardhii. Mastocarpus cristatus represents a species closely allied to Clade 3 (Mastocarpus intermedius), and M. pacificus represents Clade 7. Morphological and anatomical diagnoses, along with vertical distributions and geographic ranges, are provided for each species.