Table 2 Taxonomic update of Hesperophycus-Pelvetiopsis

The original separation of the sister genera Hesperophycus and Pelvetiopsis was based on their evident morphological differences. However, the number of eggs per oogonium, the main phenetic character used to circumscribe genera in the Fucaceae, is identical (n = 1) in and unique to these genera. Genetic distances, as assessed with ITS (Serrão et al. [24]), multiple protein-coding loci (Cánovas et al. [40]) and mtDNA (this study, including P. arborescens), are invariably of the same order of magnitude as those separating the two main lineages within the sister genus Fucus. These genera produced a viable hybrid polyploid taxon, P. hybrida, which is genetically intermediate between them. In the absence of sufficient molecular or reproductive divergence to justify two distinct genera, Hesperophycus and Pelvetiopsis must be merged into a single, monophyletic genus containing the four extant species identified to date. These genera were typified on the same page of the same publication (Gardner [93]) to accommodate Hesperophycus harveyanus (previously Fucus harveyanus Decaisne 1864) and Pelvetiopsis limitata (previously Pelvetia fastigiata f. limitata Setchell 1905). Both names are legitimate and have equal priority. We therefore chose to keep Pelvetiopsis to minimize nomenclatural changes. In addition, the holotype of Hesperophycus was actually a specimen of Fucus, a situation that was corrected only in the early 1990’s (Silva [68]). We thus propose the extinction of the genus Hesperophycus, a new combination (Pelvetiopsis californica), and a new species (Pelvetiopsis hybrida).

Pelvetiopsis N.L. Gardner 1910

Pelvetiopsis limitata (Setchell) N.L. Gardner 1910 (type species)

Pelvetiopsis arborescens N.L. Gardner 1940

Pelvetiopsis californica (P.C. Silva) Neiva, J., Raimondi, P.T., Pearson, G.A., Serrão, E.A. comb. nov.

Basionym: Hesperophycus californicus P.C. Silva 1990 (Taxon 39: 1-8)

Pelvetiopsis hybrida Neiva, J., Raimondi, P.T., Pearson, G.A., Serrão, E.A. sp. nov.

Diagnosis: Perennial, general morphology and size similar to Pelvetiopsis limitata, but distinguished from it by the occurrence of cryptostomata on the abaxial side of young frond tips, and by blunt, usually not bifurcated, receptacles; distinguished from Pelvetiopsis californica by its smaller size (<20 cm) and by the absence of abundant cryptostomata on both sides of fronds (often arranged in lines) and on receptacles. Distinguished from P. arborescens by its larger size (>13 cm), wider fronds (2.5–5 mm width), and blunt receptacles. This is an allopolyploid species derived from P. californica and P. arborescens, as assessed by a cloned nuclear intron and multiple codominant microsatellite markers.

Holotype: Otter Point, San Miguel Island, Santa Barbara County, California, USA. 17 February 2015; Kathy Ann Miller (12-I-2015); UC2050575. Isotype: UC2050576. Paratypes: UC2050573, UC2050574. Etymology: of hybrid origin. Habitat: Marine, intertidal. Growing on average above P. californica where they co-occur. Distribution: San Luis Obispo County and San Miguel Island, California.