Phaeophysema gen. nov and Vimineoleathesia gen. nov., new brown algal genera for the minute Japanese members of the genus Leathesia

Systematic relationships between representative Leathesia species (i.e. Leathesia difformis, L. japonica, L. pulvinata and L. sphaerocephala) and related taxa (i.e. Corynophlaea cystophorae and Kurogiella saxicola) within the Ectocarpales s.l. were re-examined based on the combined DNA sequences of plastid rbcL and mitochondrial cox3 genes. Resultant molecular phylogenetic trees showed polyphyly of Leathesia species; Leathesia japonica, L. sphaerocephala and L. pulvinata (members of Leathesia section Primariae), which share solid thallus construction, grouped together with Botrytella spp. rather than L. difformis (generitype; section Leathesia), which was close to Elachista tenuis and Cladosiphon okamuranus. Leathesia japonica clustered with Botrytella species rather than L. sphaerocephala and L. pulvinata. A close phylogenetic relationship between L. japonica and Botrytella species was supported by the occurrence of the characteristic free, sympodially branching filaments forming clustered plurilocular zoidangia in L. japonica, resembling Botrytella in culture and field-collected material. Based on these molecular phylogenetic analyses and morphological characteristics, we propose the establishment of Phaeophysema gen. nov. to accommodate L. sphaerocephala and L. pulvinata, and Vimineoleathesia gen. nov. to accommodate L. japonica.