Unveiling mesophotic diversity in Hawai‘i: two new species in the genera <italic>Halopeltis</italic> and <italic>Leptofauchea</italic> (Rhodymeniales, Rhodophyta)

Abstract

Two genera of the Rhodymeniales, Halopeltis and Leptofauchea, are here reported for the first time from the Hawaiian Islands and represent the deepest records for both genera. Molecular phylogenetic analyses of cytochrome oxidase subunit I (COI), rbcL, and large subunit ribosomal DNA (LSU) sequences for Hawaiian specimens of Leptofauchea revealed one well-supported clade of Hawaiian specimens and three additional lineages. One of these clades is described here as Leptofauchea huawelau sp. nov., and is thus far known only from mesophotic depths at Penguin Bank in the Main Hawaiian Islands. L. huawelau sp. nov. is up to 21 cm, and is the largest known species. An additional lineage identified in the LSU and rbcL analyses corresponds to the recently described L. lucida from Western Australia, and is a new record for Hawai‘i. Hawaiian Halopeltis formed a well-supported clade along with H. adnata from Korea, the recently described H. tanakae from mesophotic depths in Japan, and H. willisii from North Carolina, and is here described as Halopeltis nuahilihilia sp. nov. H. nuahilihilia sp. nov. has a distinctive morphology of narrow vegetative axes that harbor constrictions along their length. The current distribution of H. nuahilihilia includes mesophotic depths around W. Maui, W. Moloka‘i, and the island of Hawai‘i in the Main Hawaiian Islands. Few reproductive characters were observed because of the small number of specimens available; however, both species are distinct based on phylogeny and morphology. These descriptions further emphasize the Hawaiian mesophotic zone as a location harboring many undescribed species of marine macroalgae.

Organellar genomic characterization of Anunuuluaehu liula representing a new genus and species of Phyllophoraceae (Gigartinales, Rhodophyta) from the mesophotic zone of Hawai‘i

“…Blade morphology comparisons reveal widespread cryptic diversity among red blades in the genera Halopeltis , Leptofauchea , and Rhodymenia , which are very similar to Anunuuluaehu in terms of vegetative anatomy but distinctly different in gametangial and tetrasporangial reproductive structures (Alvarado et al., 2022; Cabrera, Huisman, Spalding, Kosaki, & Sherwood, 2022; Cabrera, Huisman, Spalding, Kosaki, Smith, et al., 2022). Anunuuluaehu stands out as a morpho‐anatomically distinct genus within the Phyllophoraceae, characterized by its unique, branching, obcordate blades with a pronounced furrow at the center of the apices and long post‐fertilization gonimoblast filaments.…”

“…This speculation may be refined with more extensive sampling in mesophotic environments in other biogeographic regions in the Pacific, yet currently Anunuuluaehu appears to be a narrowly distributed endemic genus, located only in Hawaiian MCEs. Recent progress in macroalgal alpha taxonomy has unveiled distributional patterns of macroalgae documented only from MCEs, such as Hawaiian members in the Orders Rhodymeniales (Alvarado et al., 2022), Gigartinales (Cabrera, 2020; Cabrera, Huisman, Spalding, Kosaski, & Sherwood, 2022, Cabrera, Huisman, Spalding, Kosaski, Smith, et al, 2022; Paiano et al., 2020; Sherwood et al., 2022), Ulvales (Spalding et al., 2016), Ceramiales (Paiano et al., 2022), and Peyssonneliales (Sherwood et al., 2021a, 2021b, 2021c). The discovery of this new genus highlights an even greater level of diversity among red blades than previously known and adds to the increasing number of species or genera that are believed to be unique to these spatially remote Hawaiian Islands.…”

Phylogeography of Amansia glomerata C.Agardh (Ceramiales, Rhodomelaceae) in Hawai‘i: A Single Species with High Divergence

“…2016; Smith et al . 2016) Further, several algal species unique to Hawaiian MCEs lacking shallow water representation have been described in recent years (Alvarado et al . 2022; Cabrera et al .…”