Molecular evidence suggesting species in the zoanthid genera Palythoa and Protopalythoa (Anthozoa: Hexacorallia) are congeneric.
Taxonomic status of the zoanthid genera Palythoa and Protopalythoa has been in question for almost a century. Separation of the two genera has been based on traditional morphological methods (colony and polyp form, nematocyst size and form, and number of septa), with Palythoa polyps embedded in a well developed coenenchyme and Protopalythoa polyps standing free and clear of the coenenchyme. Here we sequenced two mitochondrial regions, the cytochrome oxidase I (COI) gene and 16S ribosomal DNA (16S rDNA) genes, from Palythoa and Protopalythoa samples from various parts of the world and performed phylogenetic analyses of the sequence data. The phylogenetic trees for both COI and 16S rDNA from Palythoa and Protopalythoa show four monophyletic groups (designated Palythoa tuberculosa, Palythoa heliodiscus, Palythoa mutuki 1, and Palythoa mutuki 2), with levels of sequence divergence (COI and 16S rDNA divergence approximately 0.0 approximately 1.1%) similar to or lower than that previously found among congeneric species within the closely related genus Zoanthus. Surprisingly, sequence differences among Palythoa tuberculosa, Palythoa mutuki 1, and Palythoa mutuki 2 were negligible (0.0 approximately 0.2% for both COI and 16S rDNA), potentially indicating relationships below the species level. Our sequences align well with the few Palythoa and Protopalythoa sequences reported to date. These findings strongly indicate that our samples represent a minimum of two and possibly up to four species (the Palythoa tuberculosa - P. mutuki 1 - P. mutuki 2 group, and P. heliodiscus) within the genus Palythoa, and that the genus Protopalythoa is erroneous nomenclature.
Research Program for Marine Biology and Ecology, Extremobiosphere Research Center, Japan Agency for Marine-Earth Science and Technology, Kanagawa 237-0061, Japan. jreimer@jamstec.go.jp
James Davis
JD
Reimer
Shusuke
S
Ono
Kiyotaka
K
Takishita
Junzo
J
Tsukahara
Tadashi
T
Maruyama
D000818:Animals; D037421:Anthozoa / Q000145:classification* / Q000201:enzymology / Q000235:genetics*; D001483:Base Sequence; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D042967:Electron Transport Complex I / Q000235:genetics*; D019143:Evolution, Molecular; D008969:Molecular Sequence Data; D010802:Phylogeny; D013045:Species Specificity
D004275:DNA, Ribosomal; D042967:Electron Transport Complex I