Coral microbiomes play crucial roles in holobiont homeostasis and adaptation. The host’s ability to
populate broad ecological niches and to cope with environmental changes seems to be related to the
flexibility of the coral microbiome. By means of high‑throughput DNA sequencing we characterized
simultaneously both bacterial (16S rRNA) and Symbiodiniaceae (ITS2) communities of four reef‑
building coral species (Mussismilia braziliensis, Mussismilia harttii, Montastraea cavernosa, and
Favia gravida) that differ in geographic distribution and niche specificity. Samples were collected in a
marginal reef system (Abrolhos, Brazil) in four sites of contrasting irradiance and turbidity. Biological
filters governed by the host are important in shaping corals’ microbiome structure. More structured
associated microbial communities by reef site tend to occur in coral species with broader geographic
and depth ranges, especially for Symbiodiniaceae, whereas the endemic and habitat‑specialist host,
M. braziliensis, has relatively more homogenous bacterial communities with more exclusive members.
Our findings lend credence to the hypothesis that higher microbiome flexibility renders corals more
adaptable to diverse environments, a trend that should be investigated in more hosts and reef areas.
