Exploring the genetic diversity of shallow-water Agariciidae (Cnidaria: Anthozoa) from the Saudi Arabian Red Sea

Scleractinian corals ascribed to the family Agariciidae represent an important component of Red Sea coral reef fauna, though little genetic data are currently available for this group, and existing information shows polyphyly in the examined mesophotic taxa from the Pacific Ocean. In this work, we provide a first genetic survey of Agariciidae from the Saudi Arabian Red Sea, based on a collection of shallow-water material (<30 m) from the Gulf of Aqaba to the Farasan Islands. Two molecular markers were sequenced to infer morphospecies monophyly and relationships, the intergenic region between COI and 16S rRNA from mitochondrial DNA and the ribosomal ITS1 region from nuclear DNA. A total of 20 morphospecies were identified based on classical macromorphological characters. Six, namely Gardineroseris planulata, Pavona maldivensis, Pavona clavus, Pavona decussata, Leptoseris fragilis, and Leptoseris yabei, were resolved with both DNA loci. The molecular boundaries among the remaining 14 species remain unclear. Our results further confirm that the morphology-based taxonomy of most agariciid species is in disagreement with genetics. In order to disentangle the systematics of these taxa, the inclusion of more sampling locations, additional variable loci, and a micromophological approach are likely needed. Our genetic data represent a first step towards the comparison of biodiversity and connectivity between the Red Sea and the rest of the Indo-Pacific.