基于线粒体Cyt b基因和CR序列的养殖貉(Nyctereutes procyonoides)种群遗传多样性和结构分析

Genetic Diversity and Structure of Captive Raccoon Dog(Nyctereutes procyonoides)Based on the Mitochondrial Cyt b Gene and CR Sequences

貉(Nyctereutes procyonoides)是一种重要的经济动物。经过50年的人工驯养繁育,国内养殖种群不断扩大,但对其遗传多样性和结构了解很少,难以开展有效的遗传管理。本研究分析了东北、华北地区养殖貉种群(N=160)的线粒体细胞色素b(Cyt b)基因和控制区(CR)序列,并与已经发表的同源序列进行比较。结果定义了5个Cyt b基因和6个CR序列单倍型,其中与俄罗斯产乌苏里亚种共享单倍型分别是3个和4个。种群遗传多样性分析表明,养殖貉种群单倍型多样性处于临界点(Hd=0.50)、核苷酸多样性处于较高水平(Pi>0.5%),但二者均明显低于俄罗斯野生乌苏里貉种群。这种遗传多样性模式可能主要是由奠基者效应(founder effect)导致的。此外,红褐色型貉遗传多样性水平显著低于野生型和白色型貉。系统发育分析表明国内养殖貉种群分为3个世系,主要是乌苏里亚种、与同亚种的俄罗斯野生种群亲缘关系密切。研究还发现有1个单倍型(CH5-DH5)与越南产指名亚种共享同一个单倍型世系。这说明建群引种中可能偶然引入了华南地区分布的指名亚种。综上分析,我国养殖貉种群已经出现遗传多样性下降的迹象,需要监控种群遗传多样性的变化,引入具有新基因型的野生貉种,制定科学的交配模式,避免近交衰退。

Raccoon dog(Nyctereutes procyonoides)is reared in captivity for its pelt.With more than 50 years of captive breeding,the captive population of raccoon dog continuously increases in China.However,little is known about the genetic diversity and structure of the captive population and this limits the effective genetic management of the captive raccoon population.In this study,we analyzed the sequences of mitochondrial Cyt b gene and CR of 160 captive individuals from northeast and north China and compared our results with published homologous sequences.We detected five haplotypes of the Cyt b gene and six haplotypes for CR,of which three and four haplotypes,respectively,were separately shared with N.p.ussuriensis in Russian wild populations.Genetic diversity analysis of these sequences revealed that haplotype diversity was at the threshold(Hd=0.50)and nucleotide diversity was high(Pi>0.005)in the captive population from China.This genetic diversity was much lower than in the same subspecies from the wild population of Russian.The pattern of genetic diversity in the captive population is primarily the result of the founder effect.Additionally,the genetic diversity of reddish-brown raccoon dog was significantly lower than of the wild-type or the Jilin white strain.Phylogenetic analysis showed that the captive population could be divided into 3 mtDNA sublineages,most of which are N.p.ussuriensis,which had close relationships with the same subspecies from the Russian wild population.We also found that only haplotype(CH5-DH5)formed a common sublineage with N.p.procyonoides from Vietnam.This suggested that a few N.p.procyonoides from south China were introduced at the founding of the captive population.The relatively low genetic diversity of captive raccoon dogs evidenced a decline in the diversity of the China populations.Therefore,we recommend monitoring of the variation in genetic diversity in China to conserve the stable growth of captive populations.Introducing raccoon dogs of varied genetic type from the wild and using reasonable mating pattern may be helpful to reduce inbreeding depression in captive populations.