Taxonomy and phylogeny of scalpellomorphan barnacles, Neolepadine collected from the deep-sea hydrothermal vents

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The deep-sea hydrothermal and cold-seep endemic barnacle genus "Neolepas" s.l. in Suborder Lepadomorpha (now called suborder Scalpellomorpha) was studied on morphology and molecular biology to clarify taxonomy. Phylogeny. Neolepas s.l. can be classified four genera Neolepas s.s. (East Pacific Ridge), Vulcanolepas (previously called Neolepas, Lau and Havre basins, Southwest Pacific), Ashinkailepas (first cold-seep form, off Hatsushima Is., and hot vent form, Okinawa Trough and Myojin Knoll), and also cold-seep and hot vent forms Leucolepas (Edison seamount and Manus Basin, Sunda Trench and Okinawa Trough) based on morphology and its differences of peduncle and its scales. This morphological taxonomy is supported by the molecular phylogeny of the 12rRNA and 16SrRNA genes in the mitochondrial DNA.Those molecular data are also supported that those four genera compose of a clade and are considered to be monophyletic. In Scalpellomorpha, the following phylogeny was obtained based on molecular biology that genus Ashinkailepas is the most primitive in the four genera, genus Vulcanolepas has derived from genus Ashinkailepas, and then two genera of Leucolepas and Neolepas have derived from genus Vulcanolepas.In genus Ashinkailepas, the Southwest Pacific population collected from the Kermadec Back-arc Basin is the most primitive, and then is evolved to two populations of Okinawa Trough and Myojin Knoll in the Northwest Pacific. This phylogenetic relationship is supported the dispersal from the Southwest to Northwest Pacific in genus Ashinkailepas.The evolutions (1) from Ashinkailepas to Vulcanolepas (Southwest Pacific), (2) from Vulcanolepas to Leucolepas (West Pacific), and (3) from Vulcanolepas to Neolepas (East Pacific and Indian Ocean) are explained to dispersal within Southwest Pacific in case of (1), dispersal from Southwest Pacific to West Pacific in case of (2), and dispersal from Southwest Pacific to East Pacific and Indian Ocean in case of (3).