南洋鼠(Chiromyscus langbianis)是亚洲特有的一种树栖鼠类,其属级分类一直存在争议,不同的分类系统将其归入白腹鼠属(Niviventer)或费氏树鼠属(Chiromyscus),影响了对其生物学特性的认识.本研究旨在通过测定和分析南洋鼠的线粒体基因组,探讨其线粒体基因组结构特征,并利用近邻相接法(neighbor-joining method,NJ)和最大似然法(maximum likeli-hood method,ML)构建22个近缘物种线粒体基因组的系统发育树,厘清南洋鼠的属级分类关系.结果表明,南洋鼠线粒体基因组总长度为16 288 bp,包含22个tRNA基因、13个蛋白编码基因、2个rRNA基因和一段非编码区(non-coding region,NCR),线粒体基因组碱基组成为 A 36.6％、T 28.9％、G 15.0％和 C 19.5％,AT 偏斜(AT-skew)为 0.092,GC 偏斜(GC-skew)为-0.337.在22个tRNA基因中,除tRNASer(AGY)缺少D环外,其余的21个tRNA基因均能够折叠成典型的三叶草结构.同时,部分tRNA基因,如tRNAPhe出现了A-A,tRNAVa1、tRNALeu、tRNAI1e出现了C-U等非经典配对,以维持tRNA二级结构的稳定性.基于近邻相接法和最大似然法构建的系统发育树表明,南洋鼠与费氏树鼠属的亲缘关系更近.进一步基于线粒体Cytb和Cox1构建的系统发育树及遗传距离分析结果,均支持南洋鼠划入费氏树鼠属.本研究为南洋鼠的分类地位和系统发育关系提供了分子证据,也为其种群遗传学的研究提供了数据参考.
Mitogenomic Structural Features of Chiromyscus langbianis and Its Genus-level Phylogenetic Relationships Based on Molecular Evidence
Chiromyscus langbianis is an exclusive arboreal rodent species found in Asia.Its taxonomic classification has been conten-tious,with its placement within either the Niviventer or Chiromyscus genus influencing our understanding of its biological characteris-tics.This study aims to elucidate the structural features of the mitochondrial genome of Chiromyscus langbianis and to construct phylo-genetic trees for 22 closely related species using both the neighbor-joining method(NJ)and maximum likelihood method(ML)to clari-fy its genus-level phylogenetic relationships.The results revealed that the mitochondrial genome of C.langbianis had a total length of 16 288 bp,comprising 22 tRNA genes,13 protein-coding genes,2 rRNA genes,and a non-coding region(NCR).The base composition was 36.6％A,28.9％T,15.0％G,and 19.5％C,with an AT-skew of 0.092 and a GC-skew of-0.337.Among the 22 tRNA genes,ex-cept for tRNASer(AGY)which lacked the D-loop,the remaining 21 tRNA genes could fold into typical cloverleaf structures.However,cer-tain tRNA genes,such as tRNAPhe with A-A,and tRNAVal,tRNALeu,tRNAIle with C-U,displayed non-typical pairing to maintain the stability of the tRNA secondary structure.Phylogenetic trees indicated a closer relationship of the species langbianis to the Chiromyscus genus.Further analysis based on mitochondrial Cytb and Cox1 supported the inclusion of langbianis within Chiromyscus.This study provides molecular evidence for the taxonomic status and phylogenetic relationships of C.langbianis,thereby contributing fundamental data for its population genetics research.
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