Hidden ancient diversification in the circumtropical lancelet Asymmetron lucayanum complex |
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Authors: | T Kon M Nohara M Nishida W Sterrer T Nishikawa |
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Institution: | (1) Department of Marine Bioscience, Ocean Research Institute, The University of Tokyo, 164-8639 Tokyo, Japan;(2) Yokohama R&D Center, HITEC Co., Ltd, 220–0005 Kanagawa, Japan;(3) Bermuda Natural History Museum, PO Box FL 145, Flatts FLBX, Bermuda;(4) The Nagoya University Museum, Nagoya University, 464–8601 Aichi, Japan |
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Abstract: | The tropical lancelet Asymmetron lucayanum (= Epigonichthys lucayanus) is distributed from the western Indian Ocean to the central Pacific Ocean, and the western Atlantic Ocean. Molecular phylogenetic analysis of mitochondrial cytochrome c oxidase subunit I (COI) sequences (1,035 bp) of A. lucayanum (80 specimens from seven localities) showed clearly that this species is genetically distinguished into three major groups of geographical populations based on neighbor-joining tree using maximum likelihood distance (HKY model with invariable sites and gamma correction), suggesting the existence of three cryptic species. Our genetic data show that (1) inter-oceanic divergence time between Clade B (the West-Central Pacific) and Clade C (the Atlantic) (d = 6.6%, ca. 12 million years ago) was smaller than intra-oceanic divergence time between Clade A (the Indo-West Pacific) and Clade B (d=39.5%, ca. 100 million years ago); (2) there are two cryptic species in the West Pacific in sympatry; and (3) high gene flow is implied between the Maldives and the Ryukyus in Clade A (10,000 km distance), the Philippines and Hawaii in Clade B (8,500 km distance), and Barbados and Bermuda in Clade C (2,200 km distance). |
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