Allozyme divergence between two groups of the Japanese spinous loach, Cobitis takatsuensis

Abstract

Phylogenetic relationships of the Chugoku-Kyushu and Shikoku groups of the Japanese spinous loach, Cobitis takatsuensis, among the diploid congeners in Japan, C. biwae and Cobitis sp. complex with Niwaella delicata as an outgroup, were investigated by analyzing 20 protein-coding loci. The two groups of C. takatsuensis are clearly diverged genetically, with the genetic distance corresponding to the species level (average D ϭ 0.27). The two groups form a monophyletic cluster (bootstrap probability, P ϭ 94.9%) that is a sister cluster of C. biwae (P ϭ 63.1%). The monophyletic cluster of the Cobitis sp. complex (P ϭ 93.2%) is the most distantly related in the genus. The present results differ mostly from the mitochondrial phylogeny previously known in which the Chugoku-Kyushu group of C. takatsuensis is connected to the eastern group of C. biwae and the Shikoku group is connected to the Cobitis sp. complex with the western group of C. biwae. The contradiction between the allozymic and mitochondrial phylogenies suggests that the Shikoku group of C. takatsuensis and the western group of C. biwae received mitochondrial introgression from the Cobitis sp. complex.

Taxonomic study of the Cobitis striata complex (Cypriniformes, Cobitidae) in Japan

“…The genetic relationships among species in previous studies reveal that C. magnostriata is most distantly related to the other three species, and C. striata and C. kaibarai are the most closely related species (Shimizu et al 2004;Kitagawa et al 2005;Saitoh et al 2010). In this study, the shape of the lamina circularis and the PMN could (Table 3).…”

Shaping of genetic structure along Pleistocene and modern river systems in the hydrochorous riparian azalea, Rhododendron ripense (Ericaceae)

“…Such population divergence caused by river modifications would also accelerate speciation. For instance, the Japanese spined loach has a similar range to that of R. ripense , characterized by the localized and disjunct distribution around the Seto Inland Sea, and includes two groups with different body color patterns: the Chugoku (Honshu)–Kyushu group has a striated pattern and the Shikoku group has a nonstriated or ambiguously striated pattern (e.g., Shimizu et al, 2004). In addition, individuals of this species from the western part of Shikoku Island were recently described as a new species, C. shikokuensis Suzawa based on morphological characteristics (Suzawa, 2006).…”

A new loach, Cobitis shikokuensis (Teleostei: Cobitidae), from Shikoku Island, Japan

“…Kitagawa et al (2001) revealed that the two groups of Cobits takatsuensis have mtDNA lineages that differ markedly from each other and do not form a monophyletic cluster. Recently, Shimizu et al (2004) discovered that the two groups diverge at the species level in terms of allozyme allelic composition, despite being the most closely related groups among the Japanese Cobitis species. They suggested that the contradiction between the mitochondrial and allozymic phylogenies of the two groups might have its Significant difference between species in each sex (female/male), Mann-Whitney U test, ** P < 0.01; * P < 0.05; ns P > 0.05 …”

“…Although they have the same karyotype (2n = 48, see Kimizuka et al, 1982), populations of Cobitis shikokuensis and C. takatsuensis exhibit perfect allelic dichotomy at 4 of 20 allozyme or protein coding loci [Nei's (1972) genetic distance value was 0.27], suggesting their species-level divergence (Shimizu et al, 2004). Kitagawa et al (2001) also indicated that the mtDNA lineages of the two species are rather different, possibly because of mtDNA introgression from the Cobitis sp.…”