# Microgeographic genomic variation and connectivity in an endangered semiaquatic mammal

## TL;DR

This study explores genetic variation and connectivity in the endangered Iberian desman, revealing patterns of gene flow and the importance of protecting aquatic and terrestrial corridors for conservation.

## Contribution

The study provides new insights into microgeographic genetic dynamics and connectivity patterns in the Iberian desman using high-resolution genomic data.

## Key findings

- Genetic analysis confirmed five major phylogeographic units and validated the assignment of new data to the Occidental unit.
- Evidence of isolation-by-distance suggests gene flow decreases with geographic distance and occurs primarily over short distances.
- Connectivity was observed along the Sabor river and between headwaters of the Sabor and Tua rivers, indicating both riverine and overland dispersal.

## Abstract

The Iberian desman (Galemys pyrenaicus), a semiaquatic mammal endemic to southwestern Europe, is listed as Endangered by the IUCN due to substantial range and population decline in recent years, with its populations now largely limited to river headwaters. This restriction to upstream locations highlights the importance of documenting genetic variation and population connectivity in Iberian desmans for effective conservation strategies. While previous studies have revealed phylogeographic structure across the range of the species, gaps remain in our understanding of the microgeographic dynamics that shape genetic exchange within specific geographic regions. This study first combined our newly generated SNP data with previous datasets to further explore genetic structure across the entire Iberian desman distribution using the 115 individuals now available. Due to differences in methodology between our study and previous studies, only 110 SNPs were available for comparison across all individuals. Nevertheless, the analysis with these SNPs confirmed the presence of the five major phylogeographic units previously described and validated the assignment of our newly generated dataset to the Occidental phylogeographic unit. Focusing on our newly generated data, we explored the microgeographic dynamics of this Occidental phylogeographic unit with a higher-resolution genomic dataset (7,604 SNPs, 14 individuals). This analysis provided evidence of isolation-by-distance (IBD), suggesting that gene flow decreases with increasing geographic distance and that dispersal occurs primarily over short distances. Focussing on the Douro river system, our genomic clustering results showed both connectivity along the best-sampled river (Sabor) and between headwaters of this and headwaters from a closely located river (Tua). Our IBD results were consistent with this, indicating riverine dispersal as well as a combination of riverine and overland dispersal at headwaters. These results highlight the importance of both aquatic and terrestrial corridors in upstream areas for maintaining connectivity. Thus, conservation efforts should prioritize the protection and restoration of riparian and terrestrial corridors, particularly in fragmented landscapes, to mitigate isolation and preserve genetic diversity in the Iberian desman. This study underscores the value of genomic approaches in conservation and contributes to a deeper understanding of the ecological and evolutionary processes that maintain population connectivity in an endangered species.

The online version contains supplementary material available at 10.1186/s12862-025-02460-1.