怒江流域多鳞荷马条鳅(Homatula pycnolepis)种群年龄结构与遗传多样性

Age structure and genetic diversity of Homatula pycnolepis in the Nujiang River basin

该文于2008年4月采自南定河支流小勐统河的多鳞荷马条鳅（Homatula pycnolepis）群体（204尾, 年龄仅为1-2龄, 缺乏≥3龄个体, 年龄结构简单）;2007—2009年采自怒江流域4个采样点的多鳞荷马条鳅群体（80尾）的Cyt b 基因与群体遗传多样性及遗传结构分析共发现44个多态位点, 仅定义4个单倍型, 总体单倍型多样性（Hd）及核苷酸多样性（Pi）分别为0.7595及0.015, 而怒江流域各采样点群体的Hd及Pi均为0, 显示各地理群体遗传多样性丧失。怒江区域组、南定河组群体之间遗传分化明显, 遗传距离为0.0356, 组间分隔时间较久。由于被分离为小种群且面临较大捕捞压力, 怒江多鳞荷马条鳅种群遗传多样性丧失, 种群年龄结构简单, 且怒江区域、南定河区域及澜沧江流域种群应被作为不同遗传管理单元而进行种群管理。

This study examined the age structure of the Loach, Homatula pycnolepis through the otolith growth rings in 204 individual specimens collected from the Xiaomengtong River of the Nujiang River （Salween River） basin in April, 2008. There were only two different age classes, 1 and 2 years of age-no 3 year olds were detected. The age structure of H. pycnolepis was simple. The complete mitochondrial DNA cytochrome b gene sequences （1140） of 80 individuals from 4 populations collected in the Nujiang River drainage were sequenced and a total of 44 variable sites were found among 4 different haplotypes. The global haplotype diversity （Hd） and nucleotide diversity （Pi） were calculated at 0.7595, 0.0151 respectively, and 0, 0 in each population, indicating a consistent lack of genetic diversity in each small population. There was obvious geographic structure in both the Nujiang River basin （NJB） group, and the Nanding River （NDR） group. The genetic distance between NJB and NDR was calculated at 0.0356, suggesting that genetic divergence resulted from long-term isolation of individual population. Such a simple age structure and a lack of genetic diversity in H. pycnolepis may potentially be due to small populations and locale fishing pressures. Accordingly, the results of this study prompt us to recommend that the NJB, NDR and Lancang River populations should be protected as three different evolutionary significant units or separated management units.