Microsatellites from clade B Symbiodinium spp. specialized for Caribbean corals in the genus Madracis

In order to determine boundaries of genetic recombination among putative 'species' of endosymbiotic dinoflagellates, nine polymorphic microsatellite loci were developed and optimized for clade B Symbiodinium designated as type 7 (B7) and two related types, B13 and B13a. Together, they form a subclade in clade B that is specific to Caribbean corals in the genus Madracis. A total of 52 samples were analysed (including 43 B7, 2 B13, 7 B13a) originating from seven Caribbean locations. Diversity indices at each haploid locus ranged from 0.302 to 0.836 and four to 14 alleles were found per locus. The loci were preliminarily cross-tested on closely related 'ancestral' B1 populations found in maze coral Meandrina meandrites and that of another host specialist, B5, from the lesser starlet coral Siderastrea radians.