The genus Lychnothamnus (Rupr.) Leonhardi is a charophyte (Charophyta) found since the Late Eocene to the present. This is the first record of the extant species L. barbatus (Meyen) Leonhardi from Taiwan, and morphological analyses, molecular analyses and scanning electron microscopy have been used to explore the phylogeny and relationships between disjunct populations from Taiwan, Australia and Europe. The oospore/gyrogonites isopolarity index (ISI = 135-166) of the population in Taiwan is similar to the ISI of oospore/gyrogonites from Australia (ISI = 140-171), but quite different from the population in Europe (ISI = 115-140). The similarity of morphological features, and nearly identical rbcL sequences in the three populations from Taiwan, Australia and Europe, suggest the isolated populations originated from one population. We suggest that the Taiwanese population L. barbatus has been dispersed from/to Australia by aquatic migratory birds.