Proceedings of CWMD International Conference 2019
September 19-21, 2019, Kumamoto University, Japan

Distribution patterns of Indo-Pacific mtDNA lineages of coral-eating sea star
(Acanthaster spp. and Culcita spp.) in the coral triangle region
Mizuki Horoiwa1, Coralie Taquet2, Suharsono3, Miguel Fortes4, Handoko Adi Susanto5, Niphon
Phongsuwan6, Ywee Chieh Tay7, Davide Seveso8,9, Enrico Montalbetti8,9, Satoshi Nagai10, Kazuo
Nadaoka11, Nalinee Thongtham12, Nina Yasuda1
1

University of Miyazaki 2University of French Polynesia 3Research Center for Oceanography,Indonesian Institute of Sciences 4University of the Philippines 5Rare, Indonesia

6Department of Marine and Coastal Resources 7National University of Singapore 8University of Milano-Bicocca 9Marine Research and High Education Center 10National Research Institute of Fisheries Science 11Tokyo
Institute of Technology 12Phuket Marine Biological Center Cape Panwa

E-mail: nina27@cc.miyazaki-u.ac.jp
Key Words: Crown-of-thorns sea star, Cushion sea star, mtDNA, Species distribution, Coral Triangle
Abstract
The center of the Coral Triangle harbors the highest marine biodiversity in the world. The highbiodiversity in this region is partly explained by vicariance and allopatric speciation between the Indianand Pacific Ocean habitats during glacial periods, followed by secondary contact of the two lineages.
Knowledge of the distribution patterns of Indian and Pacific lineages is, however, limited in the CoralTriangle, hindering the precise evaluation of biodiversity. To reveal the distribution patterns of IndoPacific Ocean lineages in the center of the Coral Triangle region, we targeted two genera of corallivorous
sea stars, namely, Acanthaster spp. and Culcita spp., as keystone species in the coral reef environment.
In the present study, we collected a total of 388 samples from 12 locations across the Indo-Pacific,including the center of the Coral Triangle. The partial CO1 mtDNA gene was sequenced to determine
mitochondrial Indo-Pacific lineages. Haplotype network analysis revealed distinct genetic clades in bothAcanthaster spp. and Culcita spp. Based on their geographic distributions, one of the clades corresponds
to the Pacific Ocean clade, while the other corresponds to the Indian Ocean clade. The divergence timeof Indo-Pacific Acanthaster spp. was 2.40-3.72 million years ago, while that of Culcita spp. was 1.812.82 million years ago, both of which fall within the Plio-Pleistocene glacial period. Furthermore, we
found that Acanthaster spp. and Culcita spp. showed similar distribution patterns. The major secondary
contact zone of the Indo-Pacific Ocean lineages was found in the western Java Sea. Pacific Ocean
lineages of Acanthaster spp. and Culcita spp. are mostly distributed in the center of the Coral Triangle
region, while the Indian Ocean lineages of the two genera were found only west of the Java Sea, exceptfor Singapore. The similarity of the distribution patterns and divergence times found between
Acanthaster spp. and Culcita spp. may be attributed to similar ecological features, such as similar life
cycles, habitats, and pelagic larval durations. Because different species may have different ecologicalrequirements, the distribution patterns of the coral predator sea stars revealed in this study may be usefulin coral reef conservation in the center of the Coral Triangle region.