New species Chara oryzae and a new section Corillionia of Chara (Charales, Charophyceae) from European Mediterranean rice fields

European paddy fields harbour a morphologically and genetically unusual charophyte that is distant from any other European species. The new species, Chara oryzae from Mediterranean rice fields, was described using an integrated approach, including scanning electron microscopy and molecular phylogenetics. The combination of monoecy, a triplostichous stem cortex with solitary spine cells, haplostephanous stipulodes, abbreviated branchlet segments with their mostly incomplete diplostichous cortication, and long undifferentiated part of a branchlet distinguish C. oryzae from other Chara species described to date. A unique set of phenotypic characteristics and lack of affinity to Chara sections and subsections prompted us to accommodate the species in a new section Corillionia of the subgenus Chara. C. oryzae could be recognized as a species non-native to Europe because it is known only in rice fields, which have been maintained for centuries in the region studied. HIGHLIGHTS • European paddy fields harbour a charophyte with unusual morphology and genotype distant from any European species.• A new species, Chara oryzae, is described using an integrated approach.• A new section, Corillionia, of the subgenus Chara is proposed.