DNA sequencing resolves species of Spongites (Corallinales, Rhodophyta) in the Northeast Pacific and South Africa, including S. agulhensis sp. nov.

DNA sequence data from a 296 base pair variable region of the plastid encoded rbcL gene was obtained from 19th century type material of Spongites decipiens and of Lithophyllum tumidum (-Pseudolithophyllum neofarlowii) and matched to field-collected material, confirming the application of these specific epithets in the northeast Pacific. Phylogenetic analyses of separate and concatenated rbcL and psbA gene sequences show that both species belong in Spongites. Based on DNA sequences, the distribution of S. decipiens is confirmed from Haida Gwaii, British Columbia, Canada, south to its type locality at San Pedro, Los Angeles County, California, whereas, Spongites tumidum is distributed from near Sitka, Alaska, to Monterey County, California. Sequence data from S. decipiens and South African specimens called Spongites yendoi confirm anatomical studies that these two species are distinct but that a previously undescribed, cryptic species, Spongites agulhensis, also is present in South Africa. Anatomically and morphologically S. agulhensis is very similar to both northeast Pacific S. decipiens and South African S. yendoi, differing from the former by a single anatomical character and from the latter by two anatomical characters. Anatomy, ecology and distributions are useful in separating the South African species of Spongites, as well as the northeast Pacific species. Sequence divergence values align with biogeographic patterns and not with anatomical similarities for these Spongites species. We question the practice of placing into synonymy geographically widely separated non-geniculate coralline algal species based solely on anatomical features that likely have resulted from convergent evolution.