陕西省异色瓢虫种群遗传结构及其多样性

异色瓢虫是一种重要的天敌昆虫,广泛应用于农业生物防治中.本研究以线粒体COII基因作为分子标记,对陕西省分布的异色瓢虫不同地理种群的遗传结构及遗传多样性进行分析,并探讨不同种群间的遗传分化程度及基因交流水平.结果表明: 在21个种群529头异色瓢虫供试样本的COII序列中,共检测到15种单倍型(Hap1～Hap15),其中Hap1和Hap2所占比例最高,分别占总群体的34.4%和37.6%.总群体单倍型多样性指数为0.732,各种群内单倍型多样性范围在0.652～0.786.种群间总基因流为10.13,总群体遗传分化指数为0.024,说明种群间整体遗传分化程度较低.陕西异色瓢虫种群在进化上呈现中性模型,群体大小保持相对稳定,种群间的遗传分化主要来自种群内部.基于Nei遗传距离构建的种群系统发育树,陕南区域种群与陕北和关中区域种群分化明显.种群间遗传分化与地理距离之间存在一定的相关性,并且区域种群的遗传结构与遗传多样性也表现出一定的地理分布模式,推测秦岭的阻隔及南北气候的差异,使陕北、关中与陕南种群间的基因交流存在阻力,导致南北种群间遗传结构和遗传多样性存在差异.

Genetic structure and diversity of Harmonia axyridis populations in Shaanxi Province,China.

Harmonia axyridis, one of the most important insect predators, has been widely used in biological control in agriculture. In this study, the mitochondrial COII gene was used as genetic marker to investigate the genetic structure and diversity of H. axyridis geographic populations distributed in Shaanxi Province. Level of genetic differentiation and gene flow among different populations of H. axyridis were analyzed. For all the 529 H. axyridis individuals from 21 populations, 15 haplotypes were observed (named as Hap1-Hap15). Hap1 and Hap2 were dominant haplotypes in all sampled individuals, accounting for 34.4% and 37.6% respectively. The overall haplotype diver-sity was 0.732, and it ranged from 0.652 to 0.786 within population. The average gene flow (N_m) among 21 populations was 10.13, and the overall F_ST value was 0.024, implying low genetic diffe-rentiation among all populations. Results from neutrality tests suggested that H. axyridis populations followed the neutral evolution model and the population size remained stable. Molecular variance analysis (AMOVA) showed high proportion of total genetic variance attributed to variations within populations. Phylogenetic tree based on Nei’s genetic distance of different geographic populations showed clear divergence between northern, central, and southern Shaanxi groups. Results from Mantel test suggested that the genetic distance was weakly correlated with geographical distance between populations. Geographical pattern of genetic structure and diversity in populations from different regions indicated weak gene flow between northern, central, and southern Shaanxi due to Qinling Mountains barrier and climate difference.