Monophyly of genera and species of characeae based on rbcL sequences, withspecial reference to Australian and European Lychnothamnus barbatus (Characeae : Charophyceae)

Sequences for the chloroplast-encoded large subunit of the Rubisco gene (rb cL) were used to rest the monophyly of multiple isolates within species, an d multiple species within genera, of green algae in the Characeae (Class Ch arophyceae). Parsimony and maximum likelihood analyses supported the monoph yly of genera and most species, with the exception of a paraphyletic assemb lage comprising isolates of two 'species', dioecious Chara connivens Salzm, ex A.Br. and monoecious C. globularis Thuill., which together constitute a monophyletic group. The rbcL data support the independent evolution of eit her monoecious or dioecious sexual systems in the two connivens-globularis, clades. Comparisons of disjunct isolates of the monotypic Lychnothamnus ba rbatus (Meyen) Leohn. revealed nearly identical rbcL sequences in isolates from Croatia, Germany and Australia, although all three sequences were uniq ue. The variation exhibited by these isolates was similar to variation betw een isolates within species of Chara and Lamprothamnium from different cont inents. The limited variation may be due to dispersal of thalli or oospores between continents; however, the rarity of known intercontinental transfer s of Characeae in the last two centuries suggests that the Australian popul ation is probably not an exotic from Europe. Lychnothamnus barbatus populat ions in Australia and elsewhere thus merit continued protected status.