Data from: New species of closely related endosymbiotic dinoflagellates in the Greater Caribbean have niches corresponding to host coral phylogeny

Symbiotic dinoflagellates in the genus Breviolum (formerly Symbiodinium
Clade B) dominate coral communities in shallow waters across the Greater
Caribbean. While some formally described species exist, mounting genetic,
and ecological evidence indicate that numerous more comprise this genus,
many of which are closely related. To test this, colonies of common
reef‐building corals were sampled across a large geographical range.
Phylogenetic and population genetic markers then used to examine
evolutionary divergence and delineate boundaries of genetic recombination.
Three new candidate species were distinguished by fixed differences in
nucleotide sequences from nuclear and chloroplast DNA. Population
connectivity was evident within each lineage over thousands of kilometers,
however, substantial genetic structure persisted between lineages
co‐occurring within sampling locations, signifying reproductive isolation.
While geographically widespread with overlapping distributions, each
species is ecologically distinct, exhibiting specific mutualisms with
phylogenetically distinct coral hosts. Moreover, significant differences
in mean cell sizes provide some morphological evidence substantiating
formal species distinctions. In providing evidence that satisfies the
biological, phylogenetic, ecological, and morphological species concepts,
we classify and formally name Breviolum faviinorum n. sp., primarily
associated with Caribbean corals belonging to the Caribbean subfamily
Faviinae; B. meandrinium n. sp., associated with corals belonging to the
family Meandrinidae; and B. dendrogyrum n. sp., a symbiont harbored
exclusively by the threatened coral Dendrogyra cylindrus. These findings
support the primary importance of niche diversification (i.e. host
habitat) in the speciation of symbiotic dinoflagellates.