Microsatellite loci for Symbiodinium A3 (S. fitti) a common algal symbiont among Caribbean Acropora (stony corals) and Indo-Pacific giant clams (Tridacna)

We developed ten polymorphic microsatellite loci for S. fitti (type A3), and tested their utility on a Caribbean population associated with the coral Acropora palmata and an Indo-Pacific population harbored by the giant clam Tridacna maxima. Our analyses identified from 3 to 8 alleles for each haploid locus. Diversity (R) indices were 0.48 for the Indo-Pacific and 0.81 for the Caribbean. Greater than 95% of the samples possessed a single, symbiont, multilocus genotype (MLG). Among their many uses for the study of coral-algal symbioses, population genetic markers provide insight on the potential for symbiont dispersal, can be used to assess symbiont population stability/longevity in hospite, and partition symbiont diversity into reproductively isolated operational taxonomic units (i.e. species).