Lineage-specific variation in the evolutionary stability of coral photosymbiosis.

Over half of reef-building corals (Scleractinia) participate in a
nutritional symbiosis, known as photosymbiosis, with photosynthetic
dinoflagellates that ranges from obligate to facultative dependence.
Fitting hidden-rates models allowing among-lineage variation in the rate
of trait evolution to supertree and molecular phylogenies of Scleractinia,
we reconstruct the history of photosymbiosis within Scleractinia and
characterize its evolutionary stability. We find that most lineages of
scleractinians are extraordinarily stable for the trait, evincing no
instances of loss, but that in some clades photosymbiosis is more labile,
thus providing a framework for comparative studies to further our
mechanistic understanding of the factors that shape the evolutionary fates
of scleractinian photosymbiosis.