Fungia fungites (Linnaeus, 1758) (Scleractinia, Fungiidae) is a species complex that conceals large phenotypic variation and a previously unrecognized genus

Recent molecular phylogenetic analyses of scleractinian corals have resulted in the discovery of cryptic lineages. To understand species diversity in corals, these lineages need to be taxonomically defined. In the present study, we report the discovery of a distinct lineage obscured by the traditional morphological variation of Fungia fungites. This taxon exists as two distinct morphs: attached and unattached. Molecular phylogenetic analyses using mitochondrial COI and nuclear ITS markers as well as morphological comparisons were performed to clarify their phylogenetic relationships and taxonomic positions. Molecular data revealed that F. fungites consists of two genetically distinct clades (A and B). Clade A is sister to a lineage including Danafungia scruposa and Halomitra pileus, while clade B formed an independent lineage genetically distant from these three species. The two morphs were also found to be included in both clades, although the attached morph was predominantly found in clade A. Morphologically, both clades were statistically different in density of septal dentation, septal number, and septal teeth shape. These results indicate that F. fungites as presently recognized is actually a species complex including at least two species. After checking type specimens, we conclude that specimens in clade A represent true F. fungites with two morphs (unattached and attached) and that all of those in clade B represent an unknown species and genus comprising an unattached morph with only one exception. These findings suggest that more unrecognized taxa with hitherto unnoticed morphological differences can be present among scleractinian corals.