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

Thirteen representatives of the freshwater red algal order Batrachospermale s from Australia were analyzed with previously published sequences in a phy logenetic analysis of RUBISCO large subunit (rbcL) gene sequence data. The newly sequenced taxa represented putative endemics to the Australia-New Zea land region (Batrachospermum antipodites, B, deminutum, B. discors, B, kraf tsii, B, theaquum, B. wattsii, and Nothocladus lindaueri) and more cosmopol itan species (B, ambiguum B, atrum, B, cayennense, B, gelatinosum [two samp les], and Sirodotia suecica). From parsimony, distance, and maximum likelih ood analyses, three clades of batrachospermalean taxa were suggested: a "mi xed" clade composed of taxa sampled from Australia and North America, a dad e of primarily Australian collections, and a clade of predominantly North A merican samples. The latter two clades appeared to be more closely related to each other than to the mixed clade. It is hypothesized that the Australi an 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 Aust ralian collections. Unlike the B. gelatinosum results, B, atrum and S, suec ica 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 descripti on for section Contorts is proposed to accommodate species from section Hyb rida. The validity of Batrachospermum section Aristata is questioned based on the distant relationship of B, macrosporum and B, cayennense.