Comparative phylogeography of bagrid catfishes in Taiwan Katsutoshi Watanabe 1* , Nian-Hong Jang-Liaw 2 , Chun-Guang Zhang 3 , Sang-Rin Jeon 4 , and Mutsumi Nishida 5 1 Department of Zoology, Division of Biological Science, Graduate School of Science, Kyoto University, Kitashirakawa- Oiwakecho, Sakyo-ku, Kyoto 606-8502, Japan (e-mail: watanak@terra.zool.kyoto-u.ac.jp) 2 Department of Zoology, National Museum of Natural Science, 1st Kuan-Chien Rd., Taichung 404, Taiwan 3 Institute of Zoology, Chinese Academy of Sciences, 25 Beisihuan Xilu, Haidian, Beijing 100080, P.R. China 4 Department of Biology, College of Natural Sciences, Sang Myung University, 7 Hongji-dong, Jongno-gu, Seoul 110-743, Korea 5 Ocean Research Institute, The University of Tokyo, 1-15-1 Minamidai, Nakano-ku, Tokyo 164-8639, Japan Received: December 2, 2006 / Revised: February 23, 2007 / Accepted: February 23, 2007 Abstract A phylogeographic analysis of two bagrid catfishes in Taiwan was conducted using sequence data from a portion of the mitochondrial DNA (mtDNA) control region. For Pseudobagrus brevia- nalis, which is most probably endemic to Taiwan, a total of eight haplotypes were detected in 189 specimens from nine river systems covering its entire distribution range, from northern to central western areas of the island. Obvious genetic differentiation was observed among its populations (average F ST = 0.753); in particular, the northernmost Tamsui River population was fixed for a single endemic haplotype. Nested clade phylogeographic analysis (NCPA) indicated that the dispersal center of mtDNA was the area around the Touchien River and Holong River, north to the Miaoli Plateau, in northwestern Taiwan, suggesting both northward and southward dispersal in this species. There was no evidence for the validity of P. taiwanensis, the nominal species described from Taiwan, mor- phologically similar to P. brevianalis. We confirmed that P. adiposalis was distributed discontinuously in three river systems; analysis of 42 specimens from the rivers indicated a total of four haplotypes and population differentiation (average F ST = 0.876). Fixation into a largely differentiated haplotype in the northernmost Tamsui River population was also found in this species, but different processes for this phylogeographic pattern were implied for the two species. Comparison with P. ussuriensis, a widespread continental species morphologically similar to P. adiposalis, suggested the possibility that P. adiposalis is a group of local populations of P. ussuriensis in Taiwan. Two migration routes vs. random fixation scenarios for the population structure of P. adiposalis are discussed with information on other fishes and the geological history of the island. Key words Control region · mtDNA · Pseudobagrus adiposalis · Pseudobagrus brevianalis · Pseudo- bagrus ussuriensis widespread cyprinid species have revealed patterns of genetic divergence among geographic populations that partly conflict with the results from the faunal analysis (Wang HY et al., 1999; Wang JP et al., 2000, 2004). However, only a few species have been analyzed to date, and no fish groups have been compared simultaneously and in detail with specimens of continental relatives. The Bagridae (Siluriformes) is a large group distributed from Africa to East Asia. Approximately 40 species of Pseudobagrus and related genera occur in East Asia (Mo, 1991; Watanabe, 1995; Zheng and Dai, 1999). From Taiwan, three species have been described: Pseudobagrus breviana- lis Regan, 1908, Pseudobagrus adiposalis Oshima, 1919, and Pseudobagrus taiwanensis Oshima, 1919. Although the tax- onomy of bagrids in East Asia, including Taiwan, is largely confused, there are at least two morphological forms of bagrid in Taiwan. One form has an emarginated caudal fin with a white margin, short maxillary barbels not reaching the posterior edge of the opercle, and pectoral spines Ichthyological Research ©The Ichthyological Society of Japan 2007 Ichthyol Res (2007) 54: 253–261 DOI 10.1007/s10228-007-0398-y T he subtropical-to-tropical island of Taiwan (35 800 km 2 ) is located east of continental China and manifests great biodiversity (Lee, 2004; Shao et al., 2006). The island’s fauna is diverse and complicated as a result of its geographi- cal history, with repeated isolation from and connection to the continent, and because of the topographical, climatic, and ecological diversity of the island. Several phylogenetic and phylogeographic studies were recently conducted on mammals (Yu and Peng, 2002), reptiles (Creer et al., 2001), amphibians (Yang et al., 1994), and fishes (Wang et al., 2000, 2004), and scenarios were proposed for the origin and formation of the fauna of Taiwan. Primary freshwater fishes provide excellent opportunities for historical biogeographical studies because of their restricted dispersal in freshwater systems. Tzeng (1986) pro- posed three main zoogeographic districts and discussed the origin and formation of the distribution patterns of fresh- water fishes based on comparisons of regional faunas within the island of Taiwan. Recent phylogeographic studies on