Insights into the phylogeny of the Batrachospermales (Rhodophyta) from rbcL sequence data of Australian taxa

Thirteen representatives of the freshwater red algal order Batrachospermales from Australia were analyzed with previously published sequences in a phylogenetic analysis of RUBISCO large subunit (rbcL) gene sequence data. The newly sequenced taxa represented putative endemics to the Australia-New Zealand region (Batrachospermum antipodites, B, deminutum, B. discors, B, kraftsii, B, theaquum, B. wattsii, and Nothocladus lindaueri) and more cosmopolitan species (B, ambiguum B, atrum, B, cayennense, B, gelatinosum [two samples], and Sirodotia suecica). From parsimony, distance, and maximum likelihood analyses, three clades of batrachospermalean taxa were suggested: a "mixed" clade composed of taxa sampled from Australia and North America, a dade of primarily Australian collections, and a clade of predominantly North American samples. The latter two clades appeared to be more closely related to each other than to the mixed clade. It is hypothesized that the Australian clade may be of Gondwanic origin, but more sampling of other continents is needed to confirm this statement. The collections of B, gelatinosum from Australia did not form a monophyletic clade with B, gelatinosum from North America, and a new species, B, pseudogelatinosum, is proposed for the Australian collections. Unlike the B. gelatinosum results, B, atrum and S, suecica samples from Australia were very closely related to collections of the same species from other continents, With the addition of B. deminutum and B, ambiguum to the analysis, Batrachosperum section Contorta is shown to be monophyletic if section Hybrida is included. The expansion of the description for section Contorts is proposed to accommodate species from section Hybrida. The validity of Batrachospermum section Aristata is questioned based on the distant relationship of B, macrosporum and B, cayennense.