title: Phylogenetic relationships and natural hybridization in rabbitfishes (Teleostei: Siganidae) inferred from mitochondrial and nuclear DNA analyses.
abstract: Phylogenetic relationships of rabbitfishes (the family Siganidae), ecologically important components as primary consumers in coral reef communities, were studied using mitochondrial cytochrome b gene and nuclear ITS1 (internal transcribed spacer 1) sequence analyses. The analyses of 19 out of 22 species known in the Western Pacific region revealed that siganids are genetically clustered into three major clades, which are characterized by some morphological and ecological traits. Between closely related species, such as Siganus guttatus-S. lineatus and S. virgatus-S. doliatus, and also between two morphs recognized in S. corallinus, small but discernible genetic differentiation was found, implying that the components of each pair are incipient species. On the other hand, between some species, such as S. fuscescens-S. canaliculatus and S. unimaculatus-S.vulpinus, individuals of the components of each pair were found to construct a genetic mosaic, suggesting that the components are genetic color morphs within a single biological species, respectively. Moreover, evidence from morphological characters, mtDNA, and nuclear DNA gave an inconsistent picture of identity and relationships for several individuals. They were regarded as hybrids or individuals with hybrid origin. Such instances were observed not only between closely related species, such as S. guttatus-S. lineatus, S. virgatus-S. doliatus, and two morphs (incipient species) in S. corallinus, respectively, but also between distantly related ones, such as S. corallinus-S. puellus. In fact, more than half of the species examined (11/20, when treating the two morphs in S. corallinus as independent species) were involved in hybridization. These suggest that hybridization is much more prevalent in marine fishes than previously assumed, and may have some relevance to their diversification.
authors.affiliation: Department of Marine Bioscience, Ocean Research Institute, The University of Tokyo, 1-15-1 Minamidai, Nakano-ku, Tokyo 164-8639, Japan. kuriiwa@ori.u-tokyo.ac.jp
authors.forename: Kaoru
authors.initials: K
authors.lastname: Kuriiwa
authors.forename: Naoto
authors.initials: N
authors.lastname: Hanzawa
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Yoshino
authors.forename: Seishi
authors.initials: S
authors.lastname: Kimura
authors.forename: Mutsumi
authors.initials: M
authors.lastname: Nishida
mesh_terms: D000818:Animals; D001483:Base Sequence; D002467:Cell Nucleus / Q000235:genetics; D002678:Chimera / Q000235:genetics*; D003433:Crosses, Genetic; D045303:Cytochromes b / Q000235:genetics; D021901:DNA, Intergenic / Q000235:genetics; D004272:DNA, Mitochondrial / Q000032:analysis*; D019143:Evolution, Molecular; D008954:Models, Biological; D008969:Molecular Sequence Data; D044349:Oceania; D010473:Perciformes / Q000145:classification* / Q000235:genetics*; D010802:Phylogeny; D017422:Sequence Analysis, DNA; D012689:Sequence Homology, Nucleic Acid
chemical_list: D021901:DNA, Intergenic; D004272:DNA, Mitochondrial; D045303:Cytochromes b