Osmundea crispa Hollenberg 1943

Hughey, Jeffery R. & Miller, Kathy Ann, 2021, Genetic investigation of three type specimens of Osmundea (Rhodomelaceae, Rhodophyta) from the Gulf of California, Mexico and California, USA, Phytotaxa 489 (1), pp. 65-78 : 71

Osmundea crispa Hollenberg 1943

Heterotypic synonym: Laurencia scrippsensis E.Y. Dawson 1944, p. 234 .

Holotype: UC 685720, reef near Scripps Pier, La Jolla, San Diego County, California, epiphytic on Sargassum agardhianum Farlow , from pools in the lower littoral, 22.xi.1943.

This taxonomic treatment differs from that of previous workers who concluded based on morpho-anatomy that L. scrippsensis was conspecific with O. sinicola ( Dawson 1963, Abbott & Hollenberg 1976, Norris 2014). These newly generated data show that O. sinicola does not occur in California, and confirms its distribution in Baja California Sur, Mexico and the Gulf of California. Reports of O. sinicola from Panama, the Galápagos Islands, and the Western Atlantic ( Fernández-García et al. 2011, Ruiz & Ziemmeck 2011, Wynne 2011) are based on morpho-anatomy, and require molecular confirmation.

Osmundea crispa has a much wider range than previously reported, from Monterey to La Jolla, California, including Santa Cruz, San Nicolas and San Clemente islands. A single specimen from Punta Abreojos, Baja California Sur, indicates that the range of O. crispa overlaps with that of O. sinicola .

Osmundea crispa and O. sinicola have been distinguished by habitat, degree of thallus compression, color, distribution, and the presence or absence of lenticular thickenings in the medullary cells ( Dawson 1963, Abbott & Hollenberg 1976, Norris 2014), but the two species have been confused. Collections of O. crispa in Monterey were saxicolous, while in southern California it is typically epiphytic on coralline turf and other algae. Southern specimens have a greenish to whitish surface iridescence, and axes tend to be narrower than those from Monterey. In both regions, the species is prostrate and matted with erect, flattened axes of varying lengths and short or nub-like lateral branches ( Fig. 1 ). The original description of O. sinicola ( Setchell & Gardner 1924) is: “Frond epiphytic, attached by a creeping thallus, decidedly compressed, 3-6 cm. long, 2-4 mm. broad, sparsely and pinnately branched, with branches at times as long as the main frond…” We do not have field experience with this species, but specimens from the Gulf of California show plants with narrow (1-2 mm wide), branching axes arising from tangled basal systems ( Fig. 2 ). Both species exhibit plasticity in size, shape and color. Because their ranges overlap in Baja California Sur, it would be difficult to distinguish them on the basis of morphology alone in that region.

Both of the organellar genomes from the isotype of O.sinicola showed high gene synteny with other Rhodomelaceae . The complete mitogenome of O. sinicola was similar in length and gene number (25,021 bp and 44 genes) to the only other published mitogenome from the Rhodomelaceae , Vertebrata lanosa (Linnaeus) T.A.Christensen (25,337 bp and 44 genes) ( Salomaki et al. 2015). The plastid genome of O. sinicola was also similar (171,419 bp and 225 genes) to previously published genomes from the family ( Salomaki et al. 2015, Verbruggen & Costa 2015, Diaz-Tapia et al. 2017).

This study demonstrates that type specimens collected in 1917 ( O. sinicola , as Laurencia ), 1939 ( O. crispa , as Laurencia ), and 1943 ( Laurencia scrippsensis ) contain nucleic acids that are suitable for genomic and genetic marker analysis. Data from small amounts of type and historically significant specimens showed that specimens identified as O. sinicola in California are in fact O. crispa , and clarified the geographic ranges of these two species. The data also determined that L. scrippsensis is a heterotypic synonym of O. crispa rather than of O. sinicola . We again confirm that the genetic analysis of type specimens, if available and prudent, is the only current conclusive and objective way to determine the correct application of a name.

Figures

FIGURE 1. Isotype specimen of Laurencia crispa, UC 2041484, collected by G. J. Hollenberg and analyzed in this study. Bar = 3 cm.

FIGURE 2. Isotype specimen of Laurencia sinicola, UC 2041541, collected by Marchant and analyzed in this study. Bar = 3 cm.