Polysiphonia scopulorum Harvey 1855: 540

Huisman, John M., Kim, Byeongseok & Kim, Myung Sook, 2017, The phylogenetic position of Polysiphonia scopulorum (Rhodomelaceae, Rhodophyta) based on molecular analyses and morphological observations of specimens from the type locality in Western Australia, Phytotaxa 324 (1), pp. 51-62 : 55-58

publication ID	https://doi.org/ 10.11646/phytotaxa.324.1.3
persistent identifier	https://treatment.plazi.org/id/E8738509-A547-FFAA-3DF7-FBA6A5ECB4CF
treatment provided by	Felipe
scientific name	Polysiphonia scopulorum Harvey 1855: 540
status

Treatment

Polysiphonia scopulorum Harvey 1855: 540 .

Homotypic Synonyms: Vertebrata scopulorum (Harvey) Kuntze 1891: 929 ; Lophosiphonia scopulorum (Harvey) Womersley 1950: 188 .

Holotype: TCD (Harvey, Travelling Set no. 187). Note: Specimens included in Harvey’s Travelling Set are not available for loan ( Parnell et al. 2010). However, Womersley visited TCD in 1952 to examine the Harvey herbarium and his account of the species ( Womersley 1979) would have incorporated observations of type material. We therefore accept his description as representative of authentic P. scopulorum .

Type locality: Rottnest Island, Western Australia ( Harvey 1855).

Molecular vouchers: GenBank accession numbers MF139308, MF139309, MF139310.

Specimens examined: AUSTRALIA. Western Australia: Fays Bay, Rottnest Island, 31°59´16˝S, 115°31´31˝E, 11 November 2015, 151111#24-26 ( JNUB).

Description:— Plants form dense tufts, 0.7–1 cm high, epilithic, brownish or yellowish red in color ( Fig. 2A View FIGURE 2 ), with a prominent prostrate basal system from which erect axes arise endogenously every 4–6 segments of prostrate axes ( Fig. 2B, C View FIGURE 2 ). Prostrate axes are attached to the substratum by unicellular rhizoids arising from the center of pericentral cells in open connection with them ( Fig. 2D, E View FIGURE 2 ). Prostrate axes are terete, ecorticate, 60–80 μm in diameter with a segment length/diameter (L/D) ratio of 0.9–1.5 ( Fig. 2E View FIGURE 2 ). Erect branches are simple or several times forked, terete, ecorticate, 70–80 μm in diameter with each axial cell bearing 4 pericentral cells ( Fig. 2F, G & H View FIGURE 2 ). Segment L/D is 0.8–1.6 in lower segments, 1.4–2.1 in mid branch and 0.6–0.8 toward apices. A few lateral branches arise exogenously or endogenously from the apex of erect axes ( Fig. 2J–M View FIGURE 2 ), not associated with trichoblasts. Pericentral cells of erect axes include abundant discoidal rhodoplasts ( Fig. 2H, I View FIGURE 2 ). Apical cells are dome shaped, 10–13 μm long and 12–13 μm in diameter ( Fig. 2N View FIGURE 2 ). Vegetative trichoblasts or scar cells are formed one per segment, infrequently on lower parts of erect branches, and more frequent near the apices ( Fig. 2G, O, P View FIGURE 2 ). Vegetative trichoblasts are 2–3 times dichotomously branched, 400–750 μm long and 25–30 μm in diameter ( Fig. 2O View FIGURE 2 ). Adventitious branches develop from the mid or lower parts of erect axes ( Fig. 2Q View FIGURE 2 ). Tetrasporangia form one per segment in upper parts of erect axes, arranged in a slightly spiral series ( Fig. 2R,S, U View FIGURE 2 ). Tetrasporangia are subspherical, 50–60 μm in diameter, with two presporangial cover cells ( Fig. 2R, T View FIGURE 2 ). Gametophytes were not observed.

Distribution: — Womersley (1979) recorded P. scopulorum as occurring from Rottnest Island (“probably further north”) to Lawrence Rock, Victoria, later ( Womersley 2003) broadening this to the Dampier Archipelago in Western Australia and several locations in eastern Australia, north to southern Queensland. The Dampier Archipelago record has been found to represent an undescribed species (Huisman, unpublished observations) and in light of the results of the present study many other records require confirmation. Records from non-Australian locations (see Guiry & Guiry 2017, for sources) should similarly be viewed cautiously.

Habitat: —Our newly collected specimens were growing on rock with sand in the lower intertidal zone, which agrees with Harvey’s (1855) “on littoral rocks” description of the species’ habitat. According to Womersley (2003), plants occur mainly intertidal on rough-water rock surfaces exposed to surf, or in relatively calm localities, usually lower sublittoral, occasionally sublittoral on older axes of the brown alga Scaberia agardhii .