When forms meet genes: revision of the scleractinian genera Micromussa and Homophyllia (Lobophylliidae) with a description of two new species and one new genus

Abstract

The scleractinian family Lobophylliidae is undergoing a major taxonomic revision thanks to the combination of molecular and morphological data. In this study, we investigate the evolutionary relationships and the macro- and micromorphology of six nominal coral species belonging to two of the nine molecular clades of the Lobophylliidae, clades A and B, and of Symphyllia wilsoni, a lobophylliid species analyzed from a molecular point of view for the first time. Sequence data from mitochondrial DNA (COI and the intergenic spacer between COI and l-rRNA), and nuclear DNA (histone H3 and ITS region) are used to generate robust molecular phylogenies and a median-joining haplotype network. Molecular results are strongly in agreement with detailed observations of gross- and fine-scale morphology of skeletons, leading to the formal revision of the genera Micromussa and Homophyllia and the description of two newly discovered zooxanthellate shallow-water species, Micromussa pacifica sp. nov. Benzoni & Arrigoni and Micromussa indiana sp. nov. Benzoni & Arrigoni, and a new genus, Australophyllia gen. nov. Benzoni & Arrigoni. In particular, Acanthastrea lordhowensis and Montastraea multipunctata are moved into Micromussa, A. hillae is synonymized with A. bowerbanki and is transferred to Homophyllia, and a revised diagnosis for both genera is provided. Micromussa pacifica sp. nov. is described from the Gambier Islands with its distribution spanning New Caledonia and eastern Australia. Despite a superficial resemblance with Homophyllia australis, it has distinctive macroand micromorphological septal features. Micromussa indiana sp. nov., previously identified as M. amakusensis, is here described from the Gulf of Aden and the southern Red Sea as a distinct species that is genetically separated from M. amakusensis and is morphologically distinct from the latter due to its smaller corallite size and lower number of septa. Finally, molecular trees show that S. wilsoni is closely related, but molecularly separated from clades A and B, and, also based on a unique combination of corallite and sub-corallite characters, the species is moved into Australophyllia gen. nov. These findings confirm the need for using both genetic and morphological datasets for the ongoing taxonomic revision of scleractinian corals.