Biogeography of two species of Symbiodinium (Freudenthal) inhabiting the intertidal sea anemone Anthopleura elegantissima (Brandt)

We have analyzed the genetic profiles of dinoflagellate populations obtaine d from the Pacific coast sea anemone Anthopleura elegantissima (Brandt) at collection sites from Washington to California. Genetic differences within the symbiont populations of California anemones have been uncovered by rest riction length polymorphism (RFLP) analysis of the small subunit (SSU) and large subunit (LSU) ribosomal RNA genes, and by denaturing gradient gel ele ctrophoresis (DGGE) of the internal transcribed spacer region 2 (ITS 2). Th e existence of two Symbiodinium species is substantiated by sequence analys is of the variable regions V1, V2, and V3 of the SSUrDNA, which also establ ishes their phylogenetic relatedness to other members of the genus Symbiodi nium. Anemones from Washington and Oregon harbor a single dinoflagellate sp ecies, for which we propose the name S. muscatinei sp. nov. At these northe rn locations, S. muscatinei either exists alone or co-occurs with the Chlor ella-like green algal symbiont. Our results indicate that S. muscatinei cs- occurs with a second dinoflagellate, S. californium in mixed populations in central and southern California. We suggest that the geographic distributi on of these dinoflagellates is related to the temperature dine created by l atitude.