Background: The mitochondrial genome serves as a pivotal molecular marker for delving into systematic relationships and adaptive mechanisms. The genus Eothenomys (Cricetidae: Arvicolinae) has consistently attracted attention due to its similar biological characteristics and the analysis of its mitochondrial genome offers a fresh perspective for comprehending the phylogeny and adaptation within Cricetidae. 
 
Methods: We sequenced and analyzed the entire mitochondrial genome of E. olitor and utilized the 13 PCGs derived from this genome to delineate the phylogenetic relationships within the Cricetidae and further evaluated the evolutionary rate of each PCG. 
 
Result: The findings revealed that the mitochondrial genome of E. olitor was 16,351 bp in length, including 13 PCGs with ATN initiation codons, 22 tRNAs, 2 rRNAs and 1 D-loop. Apart from the nad6 and 8 tRNAs positioned on the J-strand, the majority of the genetic elements were situated on the N-strand. The phylogenetic examination yielded a robust phylogenetic tree for Cricetidae, but the placement of some genera remained contentious, which needs more integrative and effective data. Among of them, E. olitor was a sister of E. chinensis and Eothenomys was monophyletic. Moreover, a selective analysis showed that evolutionary rates are significant differences among the 13 PCGs. Among these genes, atp8 a high evolutionary rate, while cox1 has a low. This research uncovered the mitochondrial genome analysis of E. olitor, offering valuable perspectives the phylogeny and adaptation within Cricetidae.

Phylogenetic Insights from the Mitochondrial Genome of Eothenomys olitor (Thomas, 1911): A Cricetidae Perspective