Research Article Population Genetic Structure and Genetic Diversity in Twisted-Jaw Fish, Belodontichthys truncatus Kottelat & Ng, 1999 (Siluriformes: Siluridae), from Mekong Basin Surapon Yodsiri, 1,2 Komgrit Wongpakam, 1,2 Adisak Ardharn, 1,2 Chadaporn Senakun, 1,2 and Sutthira Khumkratok 1,2 1 Walai Rukhavej Botanical Research Institute, Mahasarakham University, Kantharawichai District, Maha Sarakham 44150, ailand 2 Biodiversity and Conservation Research Unit, Walai Rukhavej Botanical Research Institute, Mahasarakham University, Kantharawichai District, Maha Sarakham 44150, ailand Correspondence should be addressed to Komgrit Wongpakam; komgrit w@yahoo.com Received 15 February 2017; Accepted 11 July 2017; Published 16 August 2017 Academic Editor: Marco Cucco Copyright © 2017 Surapon Yodsiri et al. is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. e Mekong River and its tributaries possess the second highest diversity in fish species in the world. However, the fish biodiversity in this river is threatened by several human activities, such as hydropower plant construction. Understanding the genetic diversity and genetic structure of the species is important for natural resource management. Belodontichthys truncatus Kottelat & Ng is endemic to the Mekong River basin and is an important food source for people in this area. In this study, the genetic diversity, genetic structure, and demographic history of the twisted-jaw fish, B. truncatus, were investigated using mitochondrial cytochrome b gene sequences. A total of 124 fish specimens were collected from 10 locations in the Mekong and its tributaries. Relatively high genetic diversity was found in populations of B. truncatus compared to other catfish species in the Mekong River. e genetic structure analysis revealed that a population from the Chi River in ailand was genetically significantly different from other populations, which is possibly due to the effect of genetic driſt. Demographic history analysis indicated that B. truncatus has undergone recent demographic expansion dating back to the end of the Pleistocene glaciation. 1. Introduction e Mekong is the second most biodiverse river for fish species. It has been estimated that more than 877 fish species can be recorded in the Mekong and its tributaries [1]. However, many species are under threat due to human- mediated environmental change, such as hydropower dam construction [1, 2]. e twisted-jaw catfish (Belodontichthys truncatus Kotte- lat & Ng) is endemic to the Mekong basin [3]. Two species of the genus Belodontichthys are found in the Mekong and its tributaries, including B. dinema Bleeker, 1851, and B. truncatus. e former species occur in central and southern ailand, Malaysia, Sumatra, and Borneo, while the latter species is found in northeast ailand, Lao PDR, Cambodia, and Vietnam [3]. Belodontichthys truncatus is a very impor- tant species for fisheries in Lao PDR and Cambodia where the fish is caught and exported to ailand [4]. However, there is no information on the genetic diversity and genetic structure of this important fish, despite being important for natural resource management [5]. In this study, we used the mitochondrial cytochrome b (cyt b) sequences to examine the genetic diversity, genetic structure, and demographic history of B. truncatus in the Mekong and two of its tributaries, the Chi and Mun Rivers in northeastern ailand. Previous studies indicated that cyt b sequences can be successfully used to infer genetic structure and demographic history of freshwater fishes [6– 8]. e information presented in this study will be useful for the management of B. truncatus. In addition, because this species is widely distributed in the Mekong and its tributaries, understanding its genetic structure and demographic history would shed some light on the effect of historical change Hindawi International Journal of Zoology Volume 2017, Article ID 5976421, 7 pages https://doi.org/10.1155/2017/5976421