# Elucidating the genetic architecture of migratory timing in a songbird migrant, the great reed warbler, Acrocephalus arundinaceus

## TL;DR

This study explores the genetic basis of migration timing in great reed warblers, finding that spring migration is more genetically influenced than autumn migration.

## Contribution

The study identifies candidate genes related to lipid hydrolysis and epigenetic processes influencing spring migration timing in great reed warblers.

## Key findings

- Spring migration timing has a larger genetic contribution (effect size 0.03) compared to autumn migration (effect size 0.001).
- 93 candidate genes enriched for lipid hydrolysis functions were identified in early versus late spring migration pools.

## Abstract

Great reed warblers (Acrocephalus arundinaceus) have become an important species for understanding long-distance avian migration, yet the genetic basis of their migratory timing remains unknown. While previous studies have identified candidate genes influencing migration timing in other species, their role in great reed warblers remains unexplored. Additionally, it is unclear whether the genetic basis of migratory timing differs between spring and autumn migrations. This study aims to uncover genetic factors influencing migration timing, providing insights into the evolutionary and ecological processes shaping long-distance migration. We conducted pooled whole-genome sequencing representing four great reed warbler migratory chronotypes: early spring, late spring, early autumn, and late autumn. By comparing FST and allele frequency differences, we determined that the spring migration had a larger genetic contribution than the autumn migration; however, the effect sizes were small (0.03 and 0.001, respectively). When comparing the early and late spring pools, we identified 93 candidate genes enriched for functions related to lipid hydrolysis that putatively influence great reed warbler migratory behavior. Our results provide insight into the genetic differentiation underlying migratory timing in great reed warblers, which is crucial for predicting how they will adapt to shifting environmental conditions due to climate change and habitat loss.

Summary: Spring migratory timing in great reed warblers has a larger genetic contribution than autumn migratory timing with genes associated with lipid hydrolysis and epigenetic processes playing a key role.