尼罗罗非鱼人工驯养、选育群体遗传多样性及瓶颈效应

人工驯养和选育是家养动物适应性进化的主要动力之一,中国大陆尼罗罗非鱼引进群体经历了长期的人工驯养和选育,是研究鱼类在驯养、选育条件下适应性进化的良好材料。本实验以尼罗罗非鱼1个埃及土著群体为对照组,以中国大陆具有代表性的尼罗罗非鱼5个驯养群体和4个选育群体为实验组,采用12个多态性微卫星位点分析了驯养群体和选育群体的遗传多样性和瓶颈效应。结果显示,土著群体、驯养群体和选育群体平均每个位点的有效等位基因数(AE)分别为5.433、5.113~6.515和3.239~6.734,期望杂合度(HE)分别为0.812、0.796~0.859和0.657~0.858,多态信息含量(PIC)分别为0.768、0.753~0.819和0.601~0.818,近交系数(FIS)分别为0.323、0.166~0.342和0.249~0.314。LSDt检验结果显示,受人工选择的群体(驯养群体、选育群体)与土著群体间遗传多样性水平(AE和HE)无差异,3个驯养群体(EGY群体、WY群体和GD群体)的遗传多样性水平(HE)显著高于1个选育群体(XJF群体)。瓶颈效应分析显示,尼罗罗非鱼土著群体、驯养群体和选育群体在历史上都曾发生过群体缩小的现象。其中,土著群体、2个驯养群体(WY、EGY)、2个选育群体(JNM、XJF)在近期可能经历过遗传瓶颈,其他群体在新的突变和基因流的作用下,群体规模可能已恢复。有效群体大小分析显示,土著群体、驯养群体和选育群体的有效群体数量分别为177、29~117(平均值为57.4)和84~123(平均值为102.8)。本研究结果不仅为尼罗罗非鱼驯养群体的持续利用和选育群体的进一步遗传改良提供了有价值的信息,而且为鱼类在驯养和选育条件下群体遗传结构和种群动态研究提供了新的参考依据。

Analysis of genetic diversity and genetic bottleneck in Oreochromis niloticus populations under domestication and selective breeding

Domestication and selective breeding become one of the main driving force of adaptive evolution for domestic animals. The introduced populations of Nile tilapia(Oreochromis niloticus) in China mainland have experienced a long-term domestication and selective breeding, which provide a unique opportunity to study adaptive evolution of fish species under domestication and selective breeding. In this study, we screened 12 polymorphic microsatellite loci in nine independent-reared strains (four of which were used for selective breeding and five for ranching) and their wild progenitor population of Nile tilapia to assess genetic diversity and genetic bottleneck across native, domesticated and selective breeding populations. The parameters of genetic variability in native, domesticated and selective breeding populations were summarized as follows:the average number of effective alleles (A_E) was 5.433, 5.113-6.515, 3.239-6.734; the value of average expected heterozygosity (H_E) was 0.812, 0.796-0.859, 0.657-0.858; the value of average polymorphism information content (PIC) was 0.768, 0.753-0.819, 0.601-0.818; the value of average Wright''s inbreeding coefficient (F_IS) was 0.323, 0.166-0.342, 0.249-0.314. LSD-t test showed that no significant differences were detected between native population and populations under artificial selection(domesticated and selective breeding populations) in terms of A_E and H_E. The H_E values in three domesticated populations (EGY,WY and GD) were significantly higher than that in one selective breeding population(XJF).Analysis of bottleneck revealed that all populations have experienced a historical population bottleneck. Moreover, recent genetic population bottleneck was detected in native population, two domesticated populations (WY and EGY) and two selective breeding populations (JNM and XJF). The size of other historically bottlenecked populations may have been restored through new mutations and gene flow. The effective population sizes (N_E) of native, domesticated and selective breeding populations were 177, 29-117 (an average of 57.4), 84-123 (an average of 102.8), respectively. The results of this study provided valuable information not only for the sustainable use of domesticated populations, but also for further genetic improvement of selective breeding populations of Nile tilapia. More importantly, the findings of this study provided a new reference basis for population structure and population dynamics of fish species under domestication and selective breeding.