Phylogeny of two Symbiodinium sp from anemones in Xisha Archipelago and Hainan Island, China

Dinoflagellate algae of the genus of Symbiodinium are important symbionts within sea anemones and other marine invertebrate species. In the present study, two isolates of Symbiodinium were isolated from the two anemones, Radianthus macrodactylus and Stichodactyla mertensii, collected from Xisha archipelago and Hainan Island, China, and characterized by the use of ITS-rDNA sequences. Sequence comparison showed that sequences of the internal transcribed spacer (ITS) including 5.8S-rDNA of the two species were highly homologous, similarity above 99%. Phylogenetic reconstruction analysis with Neighbor-Joining (NJ) method and maximum parsimony (MP) method using ITS-rDNA sequences and 5.8S-rDNA region indicated that two isolates of Symbiodinium had a very close relationship and they belonged to clade Cl. Closely related symbiotic algae were found in different hosts, suggesting that animal and algal lineages had maintained a flexible evolutionary relation with each other.