Morpho-Molecular Evidence for Polymorphism in the Mushroom CoralCycloseris hexagonalis(Scleractinia: Fungiidae), with a New Phylogenetic Position and the Establishment of a New Genus for the Species

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.

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

“…After sampling, a fragment (<1 cm3) of each specimen was preserved in CHAOS solution (4M guanidine thiocyanate, 0.1% N-lauroyl sarcosine sodium, 10mM Tris-HCl pH 8, 0.1M 2-mercaptoethanol; Fukami et al, 2004) for DNA analysis, and the remnant samples were bleached for morphological analysis. In addition, we also collected specimens of Danafungia scruposa (Klunzinger, 1879) and Halomitra pileus (Linnaeus, 1758), which are known to be closely related to F. fungites (Gittenberger et al, 2011;Oku et al, 2017), and Lobactis scutaria (Lamarck, 1801) as outgroup. All specimens were identified at species level, based on original descriptions and related references (e.g., Linnaeus, 1758;Lamarck, 1801;Klunzinger, 1879;Hoeksema, 1989).…”

“…The barcoding portion of the mitochondrial COI, and ITS of the nuclear ribosomal DNA (including partial 18S, ITS-1, 5.8S, ITS-2, and partial 28S) were amplified using polymerase chain reaction (PCR) with the primers COI mod F and R (Gittenberger et al, 2011) for COI, and primers 1S and 2SS (Wei et al, 2006) for ITS. PCR conditions described by Oku et al (2017) were used in this study. The DNA sequences were determined by direct sequencing using ABI3730 sequencers (Applied Biosystems, Alameda, California, USA).…”

“…MEGA was used to estimate the topologies for each marker and to conduct a bootstrap analysis (with 1000 replicates). For both COI and ITS trees, we used as outgroup L. scutaria, which is phylogenetically closest to our target species (Gittenberger et al, 2011;Oku et al, 2017). We also concatenated both markers and performed an analysis along with available DNA data to confirm the phylogenetic position of F. fungites within Fungiidae.…”

“…We also concatenated both markers and performed an analysis along with available DNA data to confirm the phylogenetic position of F. fungites within Fungiidae. These sequences were obtained from three previous studies (Fukami et al, 2008;Gittenberger et al, 2011;Oku et al, 2017), and accession numbers are included in supplementary fig. S1.…”