Phylogeny, hybridization, and life history evolution of Rhinogobius gobies in Japan, inferred from multiple nuclear gene sequences.
Rhinogobius fishes (Gobiidae) are distributed widely in East and Southeast Asia, and represent the most species-rich group of freshwater gobies with diversified life histories (i.e., amphidromous, fluvial, and lentic). To reveal their phylogenetic relationships and life history evolution patterns, we sequenced six nuclear and three mitochondrial DNA (mtDNA) loci from 18 species, mainly from the mainland of Japan and the Ryukyu Archipelago. Our phylogenetic tree based on nuclear genes resolved three major clades, including several distinct subclades. The mtDNA and nuclear DNA phylogenies showed large discordance, which strongly suggested mitochondrial introgression through large-scale interspecific hybridization in these regions. On the basis of the molecular dating using geological data as calibration points, the hybridization occurred in the early to middle Pleistocene. Reconstruction of the ancestral states of life history traits based on nuclear DNA phylogeny suggests that the evolutionary change from amphidromous to freshwater life, accompanied by egg size change, occurred independently in at least three lineages. One of these lineages showed two life history alterations, i.e., from amphidromous (small egg) to fluvial (large egg) to lentic (small egg). Although more inclusive analysis using species outside Japan should be further conducted, the present results suggest the importance of the life history evolution associated with high adaptability to freshwater environments in the remarkable species diversification in this group. Such life history divergences may have contributed to the development of reproductive isolation.
Graduate School of Science, Kyoto University, Kitashirakawa-oiwake-cho, Sakyo, Kyoto 606-8502, Japan. Electronic address: yo.yamasaki@terra.zool.kyoto-u.ac.jp.
Yo Y
YY
Yamasaki
Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, Chiba 277-8564, Japan.
Mutsumi
M
Nishida
Kawanishi-midoridai Senior High School, 1-8 Kouyoudai, Kawanishi, Hyogo 666-0115, Japan.
Toshiyuki
T
Suzuki
Faculty of Regional Studies, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan.
Takahiko
T
Mukai
Graduate School of Science, Kyoto University, Kitashirakawa-oiwake-cho, Sakyo, Kyoto 606-8502, Japan. Electronic address: watanak@terra.zool.kyoto-u.ac.jp.
Katsutoshi
K
Watanabe
D000818:Animals; D001483:Base Sequence; D005075:Biological Evolution; D002467:Cell Nucleus / Q000145:classification / Q000235:genetics; D004272:DNA, Mitochondrial / Q000145:classification / Q000235:genetics; D006824:Hybridization, Genetic; D007564:Japan; D010063:Ovum / Q000502:physiology; D010473:Perciformes / Q000145:classification* / Q000235:genetics / Q000254:growth & development; D010802:Phylogeny; D017422:Sequence Analysis, DNA
D004272:DNA, Mitochondrial
Adaptation to a novel environment; Introgressive hybridization; Life history; Nuclear gene; Rhinogobius; Speciation