Incendia lisianskiensis A.R. Sherwood sp. nov. (Fig. 1A–J)

Type: — USA. Hawai‘i, Papahānaumokuākea Marine National Monument, Kapou (Lisianski Island), 26.025277°N, 174.15694°W, 55 m depth, 30 July 2019, B. Hauk (holotype BISH 780872; ARS 09969; field code NWHI-846).

Description: Thallus crustose, prostrate, on coral rubble, reddish in color with orange markings (Fig. 1A). Thallus moderately calcified, with undulating margins, and raised ridges on the thallus surface Fig. 1A). Hypothallus filaments consisting of mostly unbranched, parallel files of rectangular cells, cells 5.0–7.0 µm in width × 16.3–19.0 µm in height, giving rise to perithallial assurgent filaments above and rhizoids below (Fig. 1B–E). Crusts thin, ranging from 120–190 µm. Perithallial assurgent filaments arising at more or less 90º angle from hypothallus (Fig. 1B–D). Cells of mid- to lower perithallus irregularly subisodiametric, 5.1–9.2 µm in width × 7.5–11.4 µm in height (Fig. 1B–D). Lower perithallial cells forming cellular projections and secondary pit connections (Fig. 1B–D). Upper perithallial cells smaller than those in the lower perithallus, isodiametric to slightly taller than broad; 3.4–7.2 µm width × 6.7–8.2 µm height (Fig. 1B,C). Rhizoids 4.8–10.0 µm diameter, medium to long, unbranched, and multicellular (Fig. 1F). Hair cells absent (Fig. 1G). Gametangial and tetrasporangial reproduction not observed.

Distribution and Habitat:— Known only from the type locality.

Etymology:— Named for the type locality.

Identification using DNA sequence data:— Neighbor-joining analysis of available COI sequences for currently recognized species of Incendia and Seiria (and other non- Peyssonnelia species in the Peyssonneliales) supported the recognition of I. lisianskiensis as a novel species (Fig. 2). The Incendia lisianskiensis COI sequence (MZ043101) differed by 7.4% (p-distance) from its most similar congener with COI representation, I. regularis K.R.Dixon, and by>9.0% from all other available Incendia COI sequences. The rbcL phylogeny (ML topology is shown, with support values from both analyses included at nodes) also indicated a close relationship between I. lisianskiensis and I. regularis, supporting the inclusion of this specimen in the genus Incendia, and the distinction of I. lisianskiensis from other Incendia taxa included in the analysis (Fig. 3).