LAUSR

ABSTRACT Female reproductive structures, especially ampullae, play a significant role in defining generic boundaries in the family Halymeniaceae, despite recent advances in phylogenetic analyses aided by molecular data. Surveys of red algae from the Korean subtidal zone have revealed new evolutionary lineages within this family. We here propose a new genus in the Halymeniaceae, Nesoia H.W.Lee & M.S.Kim, gen. nov., with a description of N. delicatula sp. nov., N. pulchella sp. nov. and N. latifolia (P. Crouan & H. Crouan ex Kützing) comb. nov., based on Halymenia latifolia. Nesoia, which constitutes a distinct lineage of the Halymeniaceae in rbcL phylogenetic trees, has a foliose thallus with a single-layered cortex and medulla of anticlinal filaments. Carpogonial ampullae bear two-celled carpogonial branches and auxiliary cell ampullae have multiple orders of branching, mostly up to three or four. The auxiliary cell ampullary system of Nesoia is a unique type previously undescribed in the Halymeniaceae: each cell of the first-order ampullary filament produces bilateral second-order filaments, and the auxiliary cell is the basal cell of one of the two second-order filaments borne on the second or third cell of the first-order filament. Discovery of the new genus Nesoia suggests the need for more careful and systematic exploration of species diversity in this group of red algae.