New species of Galene and Howella gen. nov. (Halymeniaceae, Rhodophyta) from the mesophotic zone off Bermuda

The mesophotic zone off the coast of Bermuda has been explored for macroalgae beginning with the R/V Seahawk cruises of the 1980s and most recently on the Nekton XL Catlin cruise of the R/V Baseline Explorer in 2016. In this paper, we present two new members of the Halymeniaceae discovered on these missions based upon a combined ML analysis of mitochondrial (COI-5P), plastid (rbcL) and nuclear genes (LSU), as well as morphological and anatomical characteristics. Howella gorgoniarum gen. et sp. nov. grows conspicuously on the base of soft corals, and represents one of the three species in the new genus. Two species of the non-monophyletic Thamnoclonium, T. latifrons Endlicher & Diesing and T. lemannianum Harvey from South Africa and Australia, are moved to Howella based upon their molecular phylogenetic placements. First collected offshore of Bermuda in 1960 and misidentified as Halymenia hancockii, Galene leptoclados sp. nov. represents the first species in its genus collected outside of the western Pacific.