Gelidiorariphycus gen. nov. (Gelidiales, Rhodophyta): a rare genus found in the Americas

Abstract

ABSTRACT DNA sequence analyses have demonstrated that Gelidium as currently circumscribed is not monophyletic and has three distinctive lineages: Gelidium sensu stricto that includes the generitype Gelidium corneum, the Capreolia group, and another lineage that includes two distinct clades formed by species from the eastern Pacific and western Atlantic Oceans. A new genus of small gelidioid algae, Gelidiorariphycus, is described to accommodate one of the clades in this latter lineage. Four species (Gelidiorariphycus loratus, G. gahunbooi, G. stipitatus and G. sungminbooi) segregated into this genus in single- and multi-gene phylogenies. Gelidiorariphycus is sister to a clade formed by an unidentified eastern Pacific species and Gelidium lingulatum. These clades are closely related to a clade formed by Gelidiophycus and the Capreolia group. All four Gelidiorariphycus species were morphologically similar with small thalli that have simple and distally flattened erect axes. Fertile tetrasporophytes were found to have sori with sterile margins that are acutely tapered, which may be morphologically distinctive, but determining this requires additional study. These species were rare, with only one or two samples of each collected despite Gelidiales surveys having been done in the areas where they are known. They were mainly found growing on shallow subtidal rocky shores, but a G. gahunbooi specimen was also collected at more than 30 m depth. Their small size and preference for subtidal habitats may explain the small number of specimens collected. The recognition of this new genus is a further step in the establishment of a natural classification system for genera within the Gelidiaceae.