Data from: Cryptic diversity hides host and habitat specialization In a gorgonian-algal symbiosis

Shallow water anthozoans, the major builders of modern coral reefs, enhance their metabolic and calcification rates with algal symbionts. Controversy exists over whether these anthozoan-algae associations are flexible over the lifetimes of individual hosts, promoting acclimative plasticity, or are closely linked, such that hosts and symbionts coevolve across generations. Given the diversity of algal symbionts and the morphological plasticity of many host species, cryptic variation within either partner could potentially confound studies of anthozoan-algal associations. Here, we used ribosomal, organelle, and nuclear sequences, along with microsatellite variation, to study the relationship between lineages of a common Caribbean gorgonian and its algal symbionts. The gorgonian Eunicea flexuosa is a broadcast spawner, composed of two recently diverged, genetically distinct lineages largely segregated by depth. We sampled colonies of the two lineages across depth gradients at three Caribbean locations. We find that each host lineage is associated with a unique Symbiodinium B1/184 phylotype. This relationship between host and symbiont is maintained when host colonies are reciprocally transplanted, although cases of within phylotype switching were also observed. Even when the phylotypes of both partners are present at intermediate depths, the specificity between host and symbiont lineages remained absolute. Unrecognized cryptic diversity may mask host-symbiont specificity and change the inference of evolutionary processes in mutualistic associations. Symbiotic specificity thus likely contributes to the ecological divergence of the two partners, generating species diversity within coral reefs.cp23s fragment analysisRaw fragment length data for cp32s-rDNAReduced microsatellite data 4 loci from 7 populationsReduced microsatellite data 4 loci from 7 populationsmicrostats reducedExtended microsatellite data 4 loci from 7 populationsExtended microsatellite data 4 loci from 7 populationsmicrosats extended2ITS2 fasta aligmentits2.fastaB7SYM15 fasta aligmentSequences for the flanking region of microsatellite B7SYM15B7SYM15.fastacp23s fasta aligmentcp23s.fastapsbA fasta aligmentCoding region of the chloroplast psbApsbA.fast