# Mitogenomic Insights into Phylogeny, Biogeography and Adaptive Evolution of the Genus Typhlomys (Rodentia: Platacanthomyidae)

## TL;DR

This study uses mitochondrial genomes to explore the evolutionary history and adaptations of soft-furred tree mice in southern China and northern Vietnam.

## Contribution

The study provides new insights into the phylogeny, biogeography, and adaptive evolution of the genus Typhlomys using complete mitogenome data.

## Key findings

- Typhlomys mitogenomes show stable genetic structures with variations in genome size and two distinct clades.
- The genus likely originated in Central or Southwestern China.
- The ND5 gene in T. huangshanensis shows signs of positive selection for adaptation to cold, high-elevation environments.

## Abstract

The genus Typhlomys includes small rodents from southern China and northern Vietnam known for their echolocation abilities. However, little is known about their taxonomy, life history, and environmental adaptations. This study analyzed the mitochondrial genomes of seven Typhlomys species to explore their phylogenetic relationships, origin, and adaptive traits. Results show stable genetic structures with variations in genome size and two distinct clades, including a potential new species. The genus likely originated in Central or southwestern China. Additionally, the ND5 gene in Typhlomys huangshanensis shows signs of positive selection, indicating adaptation to colder environments of higher elevation in the northernmost distribution limit of the genus. These findings enhance our understanding of Typhlomys and support conservation efforts.

Soft-furred tree mice (genus Typhlomys), which are native to southern China and northern Vietnam, are unique rodents capable of echolocation. Little is known about their taxonomy, ecology, and natural history. In this study, we generated the complete mitochondrial genomes of seven species/putative species of Typhlomys. We conducted a comprehensive comparative analysis of these mitochondrial genomes focusing on sequence length, A+T content, A/T bias, A+T-rich regions, overlapping and intergenic spacer regions, nucleotide composition, relative synonymous codon usage, ancestral distributions, and the non-synonymous/synonymous substitution ratio (Ka/Ks). Additionally, we analyzed the phylogeny and adaptive evolution of these species/putative species. The mitogenomes of Typhlomys ranged from 16,487 to 17,380 bp in length, encoding the complete set of 37 genes typically found in mammalian mitogenomes. The base composition exhibited an A+T bias. The most frequently used codons were CUA (Leu), AGC (Ser), GGA (Gly) and UUA (Leu), UUG, CUG, CGU and GCG were the less frequently used codons. Ancestral distribution reconstruction suggests that Typhlomys originated in Central or Southwestern China. Notably, we found that the Ka/Ks ratio of the ND5 gene in T. huangshanensis was greater than 1, indicating that this gene has undergone positive selection for efficient respiration in higher elevations and colder climates.