Chamberlainium (Corallinales, Rhodophyta) in South Africa, an exemplar for the study of coralline algae, description of C. tenue sp. nov., biogeography of the genus, and species keys.

• South African Chamberlainium , an exemplar for the study of coralline algal systematics • Description of Chamberlainium tenue, a new cryptic/pseudocryptic species of coralline algae • Integrated taxonomic approach using DNA sequences from historical and field specimens • Keys to all Chamberlainium species in South Africa • Biogeographic considerations Based on plastid encoded DNA sequences from psb A and rbc L markers, a new non-geniculate coralline algal species, Chamberlainium tenue , is described from South Africa that was previously passing under the misapplied name, Spongites yendoi. DNA sequences, supported by the morpho-anatomical character of tetrasporangial conceptacle roof development, placed C. tenue in Chamberlainium , subfamily Chamberlainoideae. Instead of one species, Spongites yendoi , widely distributed across the entire coastline of South Africa, seven molecularly distinct species were present under that name and all belong in Chamberlainium. Three occur in the cooler water Benguela Marine Province, C. capense, C. glebosum , and C. occidentale, the last extending into the Benguela-Agulhas Transition Zone; three occur in the warmer water Agulhas Marine Province, C. tenue, C. cochleare and C. natalense , with the latter two extending into the Benguela-Agulhas Transition Zone; two occur only in the Benguela-Agulhas Transition Zone, C. agulhense and the historically recognized, C. impar. Both the rbc L and psb A phylograms indicate that ancestral taxa gave rise to species found in both warmer and cooler water habitats. Keys to species of South African Chamberlainium are provided for use in both the field and the laboratory. The methodology used to study these Chamberlainium species, that included: 1) DNA sequencing of type specimens to correctly apply names; 2) DNA sequencing of numerous field-collected specimens; and 3) morpho-anatomical observations on these same DNA sequenced specimens, can be an exemplar for resolving the systematics and biogeography of the many unresolved and unstudied species of South African coralline algae. [ABSTRACT FROM AUTHOR]