Abstract
The soft coral family Xeniidae, commonly found in tropical and subtropical regions, consists of 20 genera and 162 species. To date, few studies on this family have been conducted in Japan, especially at higher latitudes. Although molecular phylogenetic analyses have recently been used to distinguish soft coral species, it is difficult to identify species and genera in this family due to the limited taxonomic indices and high morphological variation. In this study, we found a large Xeniidae community off the coast of Oshima Island (31°31.35'N, 131°24.27'E) at Miyazaki, Kyushu Island, located in the temperate region of Japan. The species composition and molecular phylogenetic relationships were investigated to uncover the species diversity of Xeniidae in this community. A total of 182 xeniid specimens were collected and identified to the species level, after which the samples were molecularly analyzed using a mitochondrial marker (ND2) and a nuclear marker (ITS) to infer the phylogenetic relationships. A total of 14 xeniid species were identified, including five undescribed species from five genera (Anthelia, Heteroxenia, Sympodium, Xenia, and Yamazatum). Miyazaki was identified as having the highest xeniid species diversity in Japan. The molecular phylogenetic trees inferred from each marker recovered very similar topologies: four genera (Anthelia, Heteroxenia, Sympodium, and Yamazatum) were monophyletic, whereas one (Xenia) was polyphyletic. Thus, except for Xenia, the morphological characteristics used for traditional taxonomy well reflected the phylogeny of the Xeniidae at the genus level. On the other hand, our results show that further taxonomic revisions of Xenia are needed.
Highlights
Tropical marine animals, including zooxanthellate alcyonacean corals abound in the southern part of the temperate region of Japan, due to the Kuroshio – a strong warm current running along the coast from the Ryukyu Archipelago to the mainland of Japan
The present study describes a large community of xeniids found around Oshima Island (31°31.35'N, 131°24.27'E) at Miyazaki, Kyushu Island
The present study aimed to investigate the current species diversity of the family Xeniidae around Oshima Island, Japan, and to clarify this family’s taxonomic issues at the species level, through molecular phylogenetic analyses using NADH-dehydrogenase subunit 2 gene (ND2) and internal transcribed spacer (ITS) markers
Summary
Tropical marine animals, including zooxanthellate alcyonacean corals (i.e., soft corals) abound in the southern part of the temperate region of Japan, due to the Kuroshio – a strong warm current running along the coast from the Ryukyu Archipelago to the mainland of Japan. As xeniids are uncommon in Japan, this is an unusual community Due to this area’s higher latitude, coral reef structures are usually not formed, but there are over 100 zooxanthellate scleractinian coral species (Nishihira and Veron 1995). This area was occupied previously by zooxanthellate scleractinian corals, which were damaged drastically during the 1980s by outbreaks of the coral-eating gastropod Drupella spp. and the crown-of-thorns seastar Acanthaster sp. The area is occupied mainly by xeniids, which are known as pioneer alcyonaceans in ecological succession in tropical coral reefs (Benayahu and Loya 1987). Identifying xeniid species diversity in this area is important to understand how coral communities change over time at higher latitudes
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