# Contrasting genetic diversity and ecological niche modelling of the montane grass mouse Akodon montensis in the south of the Atlantic Forest

## TL;DR

This study explores the genetic diversity and ecological history of the montane grass mouse in the Atlantic Forest, linking genetic patterns to past and present environmental changes.

## Contribution

The study integrates genetic data and ecological niche modeling to reveal how historical climate shifts shaped the genetic structure of A. montensis.

## Key findings

- Moderate genetic differentiation in some populations suggests limited gene flow due to habitat fragmentation.
- High environmental suitability during the last glacial maximum in coastal Brazil correlates with high genetic diversity.
- Extended habitat suitability in southwestern Brazil and surrounding regions supports the Atlantis Forest hypothesis.

## Abstract

Akodon montensis is widely distributed throughout the Atlantic Forest (AF) hotspot biodiversity, encompassing Brazil and reaching its southern limit in eastern Paraguay and northeastern Argentina. Here, we combined analysis of molecular data and ecological niche modelling to contribute to elucidating its evolutionary history. At a local scale, we studied the genetic variability in microsatellite loci in populations from the remaining AF in Misiones province, Argentina. The moderate genetic differentiation observed in some populations suggests that limited gene flow may result from habitat fragmentation at the south of the AF. At a wide geographic range, the ecological niche modelling identified areas of high environmental suitability for A. montensis during the last glacial maximum (LGM) on the coast of Brazil, where the forested habitats expanded onto the continental shelf. This could explain the high diversity in the cytochrome b in this region and contiguous areas, agreeing with the Atlantis Forest hypothesis. Additionally, we observed an extended area of high habitat suitability during the LGM and at present in southwestern Brazil, eastern Paraguay and northeastern Argentina. The evolutionary history of A. montensis seems to have been influenced by demographic processes that occurred at different times and regions, shaping its genetic variability and structure.