PHYLOGENETIC ANALYSES OF THE RED ALGAL ORDER RHODYMENIALES SUPPORTS RECOGNITION OF THE HYMENOCLADIACEAE FAM. NOV., FRYEELLACEAE FAM. NOV., AND NEOGASTROCLONIUM GEN. NOV.1

Systematics of the red algal order Rhodymeniales was investigated using combined large‐subunit nuclear ribosomal DNA (LSU) and elongation factor 2 (EF2) analyses. These data were subjected to distance, parsimony, and Bayesian analyses, and the resulting phylogenies were largely congruent with previously published SSU results in that the four currently recognized rhodymenialean families (Champiaceae, Faucheaceae, Lomentariaceae, and Rhodymeniaceae) were resolved as monophyletic lineages (with the exception of Coelothrix, which is here transferred to the Champiaceae from the Rhodymeniaceae). In addition, taxa presently considered as incertae sedis consisted of two lineages (Fryeella lineage and Hymenocladia lineage). Based on these results, two new families are proposed: (i) the Fryeellaceae fam. nov. to accommodate the genera Fryeella, Hymenocladiopsis, and a new taxon from Tasmania, Australia; and (ii) the Hymenocladiaceae fam. nov., to accommodate Asteromenia, Hymenocladia, and Erythrymenia. In addition to resolving familial relationships, these analyses resolved some novel interspecific affinities, and we propose a new genus, Neogastroclonium gen. nov., for Gastroclonium subarticulatum, a species that differs significantly in both morphology and molecular data from genuine species of Gastroclonium. Relationships among additional faucheacean and lomentariacean taxa were investigated using LSU data only, and these results are discussed. The familial classification of the Rhodymeniales proposed herein is discussed in light of vegetative and reproductive anatomy, most notably the ontogeny of the tetrasporangia.