No abstract

Mushroom corals are reef corals of the family Fungiidae, which live in the tropical and subtropical Indo-Pacific region. Recently, most species of this family have been revised taxonomically based on morphological and molecular analyses. However, the phylogenetic position of Cycloseris hexagonalis ( Milne Edwards and Haime, 1848 ) has not been analyzed and remains unclear. This species is believed to show allometric growth by changing its corallum shape from hexagonal in juveniles to irregularly circular with an undulated corallum margin in mature individuals. However, these morphological changes have not been monitored and their genetic basis has not been confirmed. In the present study morphological and molecular phylogenetic analyses were performed to evaluate the identity of the morpho-types in C. hexagonalis and to clarify the phylogenetic and taxonomic position of the species. In the morphological analysis, we used 20 specimens of C. hexagonalis collected from around Iriomote Island, Okinawa, Japan, and identified four morphotypes. Moreover, the molecular phylogenetic analyses using mitochondrial COI and nuclear ITS markers showed that all morpho-types of C. hexagonalis together form an independent clade, indicating that they are all conspecific. Molecular phylogenetic comparison between this species and other fungiids revealed that the clade of C. hexagonalis is clearly distant from the Cycloseris clade as well as from clades representing other genera in the Fungiidae. Considering these data, we establish a monotypic new genus, Sinuorota, to accommodate C. hexagonalis.

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.