Biodiversity of Hawaiian Peyssonneliales (Rhodophyta). 1. Two New Species in the Genus Ramicrusta from Lehua Island1

Abstract: Two specimens of the crustose red algal genus Ramicrusta were collected off Lehua Island, Hawai‘i, at 11 m and 49 m depth in September 2018, and are here described as new species on the basis of both molecular and morphological comparisons. Ramicrusta hawaiiensis sp. nov. is distinguished from the 12 other known species in the genus by the combination of its gross habit and coloration, pronounced perithallial zonation, frequent and robust rhizoids, presence of hair cells, and by distinctive COI and rbcL marker sequences, and represents a mesophotic record of the genus Ramicrusta. Similarly, Ramicrusta lehuensis sp. nov. is distinctive in the combination of its gross habit and coloration, less-pronounced perithallial zonation, presence of frequent and robust rhizoids as well as hair cells, and is also distinct in COI and rbcL marker sequences. These records constitute the first for the genus Ramicrusta in Hawai‘i, and highlight the cryptic diversity of peyssonnelioid red algae in the Hawaiian Islands. This study also adds to the growing list of novel algal species being characterized from mesophotic depths in Hawai‘i—a habitat which is being shown to contain numerous undescribed taxa and records of species and genera previously unknown to the Islands. This initial record of Ramicrusta in Hawaiian waters is noteworthy given the recent reports of members of the genus overgrowing and killing corals in the Caribbean and South China Sea.