Genetic structuring and species boundaries in the Atlantic stony coral Favia (Scleractinia, Faviidae)

Scleractinian corals are the main modern builders of coral reefs, which are major hot spots of marine biodiversity. Southern Atlantic reef corals are understudied compared to their Caribbean and Indo-Pacific counterparts and many hypotheses about their population dynamics demand further testing. We employed thousands of single nucleotide polymorphisms (SNPs) recovered via ezRAD to characterize genetic population structuring and species boundaries in the amphi-Atlantic hard coral genus Favia. Coalescent-based species delimitation (BFD* – Bayes Factor Delimitation) recovered F. fragum and F. gravida as separate species. Although our results agree with depth-related genetic structuring in F. fragum, they did not support incipient speciation of the ‘tall’ and ‘short’ morphotypes. The preferred scenario also revealed a split between two main lineages of F. gravida, one from Ascension Island and the other from Brazil. The Brazilian lineage is further divided into a species that occurs throughout the Northeastern coast and another that ranges from the Abrolhos Archipelago to the state of Espírito Santo. BFD* scenarios were corroborated by analyses of SNP matrices with varying levels of missing data and by a speciation-based delimitation approach (DELINEATE). Our results challenge current notions about Atlantic reef corals because they uncovered surprising genetic diversity in Favia and rejected the long-standing hypothesis that Abrolhos Archipelago may have served as a Pleistocenic refuge during the last glaciations.