title: Unexpected monophyletic origin of Ephoron shigae unisexual reproduction strains and their rapid expansion across Japan.
abstract: The burrowing polymitarcyid mayfly Ephoron shigae is distributed across Japan, Korea, northeast China and far east Russia. Some populations are bisexual, and others are unisexual, i.e. geographically parthenogenetic throughout Japan. In general, parthenogenetic organisms are often found in harsh environments, such as at high latitudes and altitudes, in xeric as opposed to mesic conditions, in isolated habitats such as islands and island-like areas, and at the peripheral regions of the taxon's range. In E. shigae, however, the distributions of bisexual and unisexual populations overlap broadly in their respective geographical ranges. In the analysis of mitochondrial 16S rRNA and COI, we revealed that unisexual populations were of monophyletic origin and recently differentiated somewhere in western Japan. In the nuclear DNA EFI-α analysis, parthenogenetic strains had two genotypes, i.e. the heterozygous genotype of E1/E3 and the homozygous genotype of E1/E1 or E3/E3, while specimens of bisexual lineage had 20 genotypes. These results are consistent with an automixis mode of reproduction for the parthenogenetic strains, and also support the monophyletic origin of the parthenogenetic strains. Furthermore, there would be no gene flow between the specimens of the bisexual lineage and those of the parthenogenetic strain.
authors.affiliation: Biological Science in Mountainous Area , Interdisciplinary Graduate School of Science and Technology, Shinshu University , Asahi 3-1-1, Matsumoto, Nagano 390-8621, Japan ; Division of Insect Sciences , National Institute of Agrobiological Sciences , 1-2, Owashi, Tsukuba, Ibaraki 305-8634, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Sekiné
authors.affiliation: Department of Biology , Tokyo Metropolitan University , Minamiosawa 1-1, Hachioji, Tokyo 192-0397, Japan.
authors.forename: F
authors.initials: F
authors.lastname: Hayashi
authors.affiliation: Department of Biology, Faculty of Science , Shinshu University , Asahi 3-1-1, Matsumoto, Nagano 390-8621, Japan ; Institute of Mountain Science , Shinshu University , Asahi 3-1-1, Matsumoto, Nagano 390-8621, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Tojo
keywords: automixis; geographical parthenogenesis; phylogeography; thelytoky