Taxonomy, morphology, and genetic variation of Nitella flexilis var. bifurcata (Charales, Characeae) from Japan

Abstract

The taxonomic status of Nitella flexilis var. bifurcata (Charales, Characeae), which is endemic to Japan, has remained unclear because there have been no records since its description in 1964, and the detailed morphology of fully mature individuals as well as its molecular phylogeny have not been studied. Recently, we collected a fully mature N.flexilis var. bifurcata from two lakes near the type locality in Japan. The morphological characteristics of the thalli agreed well with that in the original description of the taxon, with distinctive fertile and sterile branchlets that divided twice and unicellular dactyls. Scanning electron microscopy showed that the fine oospore structure of N.flexilis var. bifurcata was different from that of related taxa. In addition, molecular phylogenetic and haplotype network analyses using the chloroplast rbcL DNA sequences and the intergenic spacer regions between atpB and rbcL genes demonstrated that N.flexilis var. bifurcata and N.flexilis var. flexilis were distinct.