# Genetic Structure of the Cave-Dwelling Catfish Pterocryptis anomala (Siluriformes: Siluridae) in Southwest China

## TL;DR

This study explores the genetic diversity of a cave-dwelling catfish in China and how historical events shaped its population structure.

## Contribution

The study identifies two distinct genetic clades in Pterocryptis anomala and links their divergence to the Qinghai–Tibet Plateau uplift.

## Key findings

- Two distinct evolutionary clades were identified in Pterocryptis anomala populations.
- The divergence between clades occurred approximately 13.73 million years ago.
- Geographical barriers like the Nanling Mountains and river systems caused genetic differentiation.

## Abstract

This study elucidated the genetic structure and diversity of Pterocryptis anomala populations in Southwest China based on two mitochondrial and two nuclear genes and further investigated key driving factors influencing their current distribution patterns. Through phylogenetic analysis of 255 individuals, we identified two distinct evolutionary clades. The haplotype network also supported the division of all individuals into two clades. The divergence time between the two clades was estimated at 13.73 million years ago (Mya), which may have been influenced by the impact of the Qinghai–Tibet Plateau (QTP) uplift on monsoonal systems. Our findings enhance the understanding of the phylogeographic history of P. anomala in Southwest China and provide a theoretical framework for targeted conservation strategies to safeguard freshwater biodiversity in this ecologically critical region.

The mountainous regions of Southwest China are biodiversity hotspots where geographical isolation promotes genetic differentiation and species diversification. For cave-dwelling species like the Pterocryptis anomala, how geographical isolation, historical climate, and riverscapes have influenced their evolution remains largely unexplored. Based on 255 samples from the Pearl River and the Yangtze River, this study integrated two mitochondrial genes and two nuclear genes to analyze the genetic diversity and structure of the P. anomala population. Phylogenetic trees based on mitochondrial DNA revealed two distinct clades of P. anomala, while nuclear DNA loci showed no clear separation. Spatial Analysis of Molecular Variance (SAMOVA) confirmed two groups: Clade I (the Yangtze, the Guijiang, and the Duliujiang Rivers) and Clade II (the Nanpanjiang, Hongshui, Dahuanjiang, Youjiang, and Rongjiang Rivers). The divergence time between the two clades was estimated at 13.73 million years ago, which was potentially linked to the impact of the QTP uplift on monsoonal systems. The star-like network analysis and neutrality test results indicated that the population of Clade I has maintained a stable state over a long period, while the population of Clade II showed a trend of expansion. Additionally, geographical features such as the Nanling Mountains and the two major river systems may have obstructed gene flow, leading to genetic differentiation. These findings improved our understanding of this species’ evolutionary history and population structure, offering valuable insights for conservation efforts.