Species delimitation in the reef coral genera Echinophyllia and Oxypora (Scleractinia, Lobophylliidae) with a description of two new species

Scleractinian corals are affected by environment-induced phenotypic plasticity and intraspecific morphological variation caused by genotype. In an effort to identify new strategies for resolving this taxonomic issue, we applied a molecular approach for species evaluation to two closely related genera, Echinophyllia and Oxypora, for which few molecular data are available. A robust multi-locus phylogeny using DNA sequence data across four loci of both mitochondrial (COI, ATP6-NAD4) and nuclear (histone H3, ITS region) origin from 109 coral colonies was coupled with three independent putative species delimitation methods based on barcoding threshold (ABGD) and coalescence theory (PTP, GMYC). Observed overall congruence across multiple genetic analyses distinguished two traditional species (E. echinoporoides and O. convoluta), a species complex composed of E. aspera, E. orpheensis, E. tarae, and O. glabra, whereas O. lacera and E. echinata were indistinguishable with the sequenced loci. The combination of molecular species delimitation approaches and skeletal character observations allowed the description of two new reef coral species, E. bulbosa sp. n. from the Red Sea and E. gallii sp. n. from the Maldives and Mayotte. This work demonstrated the efficiency of multi-locus phylogenetic analyses and recently developed molecular species delimitation approaches as valuable tools to disentangle taxonomic issues caused by morphological ambiguities and to re-assess the diversity of scleractinian corals.