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[目的]分析中国橙黄豆粉蝶Colias fieldii种群遗传多样性和遗传分化情况及其系统发生关系,推测其起源及分化时间,并探讨其历史生物地理分布格局的成因.[方法]对2006-2018年采集的中国23个橙黄豆粉蝶地理种群的115头个体样品的4个线粒体基因(COI,Cytb,NDI和ND5)序列进行PCR扩增和测序;采用MEGA v.7.0,DnaSP v.5.0和Arlequin v.3.5.1等软件分析其遗传多样性和遗传分化情况;以其他近缘豆粉蝶种类作为外类群,采用IQ-TREE,MrBayes v.3.1.2,Network v.4.6和BEAST v.1.8.3等软件重建橙黄豆粉蝶的系统发生树和单倍型网络图,并使用宽松分子钟以及前人的时间标定推测橙黄豆粉蝶的起源和分化时间;结合现今橙黄豆粉蝶的生物地理分布特点和第四纪以来的地球环境背景,探讨其历史生物地理分布格局及成因.[结果]橙黄豆粉蝶种群4个线粒体基因(COI,Cytb,NDI和ND)5)片段长度分别为648,699,393和777 bp,这4个基因的串联序列总长为2 517 bp,具有明显的AT偏倚特征.基于4个线粒体基因序列,供试橙黄豆粉蝶23个地理种群115头个体中共检测出18个单倍型,总群体的单倍型多样性(Hd)和核苷酸多样性(π)分别为0.677 ±0.048和0.00066 ±0.00007,呈现出较高的单倍型多样性和较低的核苷酸多样性.系统发育分析表明,橙黄豆粉蝶种群的18个单倍型分为2个具有明显地理分布格局的支系(Ⅰ和Ⅱ),支系Ⅰ包含13个单倍型,主要来自陕西、河南、甘肃、安徽、湖北、四川、青海及云南部分地区的种群;支系Ⅱ由5个单倍型组成,主要来自云南部分地区及西藏的种群;单倍型网络图与系统发生树结果一致.AMOVA分析结果表明,大部分的种群遗传分化(64.36％)来自于橙黄豆粉蝶种群两单倍型支系间,各分支内的遗传分化较小(35.64％).中性检验和错配分布分析结果显示,单倍型支系Ⅰ的种群未发生过种群扩张事件,而单倍型支系Ⅱ的种群在历史上发生过种群扩张事件,扩张事件发生的时间(0.085 Ma)位于末次冰盛期前的间冰期,这一结果可能是由于间冰期温暖湿润的高原气候以及森林草原扩张、强降雨减少等因素造成的.[结论]橙黄豆粉蝶种群的遗传分化与地理距离之间存在明显的相关性.其祖先可能在距今48万年前起源于我国的西南地区(现今横断山区一带),之后,由于第四纪冰期-间冰期轮回事件、东南亚季风以及栖息地环境的影响而分化为2大支系并逐渐向低海拔地区扩散.“,”[Aim]This study aims to explore the genetic diversity,genetic differentiation,and phylogenetic relationships among populations of the pierid butterfly Colias fieldii in China,to infer their origin and divergence time,and to preliminarily clarify the causes of their spatiotemporally evolutionary history.[Methods]The four mitochondrial gene(COI,Cytb,NDI and ND5)sequences of 115 individuals from 23 geographic populations of C.fieldii in China collected in 2006-2018 were amplified by PCR and sequenced.The genetic diversity and genetic differentiation were analyzed using MEGA v.7.0,DnaSP v.5.0,Arlequin v.3.5.1 and other genetic analysis software.Using the closest relatives as the outgroups,the phylogenetic trees and haplotype median-joining network of C.fieldii were reconstructed with such analytical software as IQ-TREE,MrBayes v.3.1.2,Network v.4.6 and BEAST v.1.8.3,and the origin and divergence time of C.fieldii were estimated by using relaxed molecular dating method and calibrations of the previous studies.Based on the present biogeographic distribution of C.fieldii and the main earth environmental events since the Quaternary Period,the spatio-temporal pattern of its biogeographic distribution and the underlying earth environmental factors were tentatively inferred.[Results]The aligned sizes of mitochondrial gene segments of COI,Cytb,NDI and ND5 of C.fieldii populations are 648,699,393 and 777 bp,respectively,and the concatenated sequence of the four genes is 2 517 bp in length,which was shown to be significantly AT biased.In total,18 haplotypes based on the four mitochondrial gene sequences were found in 115 individuals of 23 geographic populations of C.fieldii,with the haplotype diversity(Hd)of 0.677 ±0.048 and nucleotide diversity(π)of 0.00066 ± 0.00007 of the total population,showing a relatively high level of haplotype diversity and a low level of nucleotide diversity.The phylogenetic analysis showed that 18 haplotypes of C.fieldii populations were distinctly categorized into two large clades(clade Ⅰ and Ⅱ).Clade Ⅰ included 13 haplotypes of populations from Shaanxi,Henan,Gansu,Anhui,Hubei,Sichuan,Qinghai,and some regions of Yunnan.Clade Ⅱ included five haplotypes of populations from some regions of Yunnan and Tibet.The results of reconstructed haplotype median-joining network were generally consistent with those of the phylogenetic tree.AMOVA analysis indicated that a larger level of population differentiation(64.36％)occurred between the two haplotype clades and a subtle genetic differentiation(35.64％)existed within each haplotype clade of C.fiieldii.The analysis results of neutrality tests and mismatch distribution indicated that populations with haplotypes in clade Ⅰ did not experience a population expansion event,whereas those with haplotypes in clade Ⅱ probably had a sudden demographic expansion at about 0.085 Ma in the late Pleistocene,a little earlier than the Last Glacial Maximum event,which may be caused by the warm and humid plateau climate in the interglacial period,the expansion of forest grassland and the decreased heavy rainfall on the core plateau.[Conclusion]The genetic differentiation of C.fieldii populations is correlated significantly with the geographical distance.In addition,we proposed that C.fieldii populations originated at about 0.48 Ma in southwestern areas of China(presently the Hengduan Mountains and adjacent areas),and began to diversify into two clades and later dispersed into other low-latitude areas due to the Quaternary glacial-interglacial cycle events,Southeast Asia monsoon and different habitat environments.