# Alternative Splicing and Gene Expression Variation Underlie Population and Life History Differences in an Amphibian

## TL;DR

Wood frogs show significant gene expression and splicing differences between life stages and populations, suggesting transcriptomic plasticity plays a key role in adaptation to environmental changes.

## Contribution

The study integrates gene expression and alternative splicing to reveal transcriptomic mechanisms underlying life history and population differences in an amphibian.

## Key findings

- Thousands of genes show differential expression or splicing between hatchlings and adults.
- Roadside and woodland populations are distinguished by two differentially expressed genes (HSP70 and Gpsm2) and one differentially spliced gene (Cd82).
- Low genetic differentiation suggests transcriptomic differences arise under gene flow and reflect plastic responses.

## Abstract

Phenotypic variation is common across life history and among populations occupying different environments, yet the molecular mechanisms underlying these axes of divergence remain poorly understood. Much work has focused on gene expression as a link between genetic variation, environmental variation, and phenotypes, but post‐transcriptional processes such as alternative splicing—which affect how transcripts are assembled rather than how much of a transcript is produced—are increasingly recognized as additional modulators of plasticity and adaptation. Here, we examined gene expression and alternative splicing together in the wood frog (
Rana sylvatica
), an amphibian with a complex life cycle whose populations differ across replicated gradients of road adjacency and associated pollution. We found extensive transcriptomic differences between hatchlings and adults, with thousands of genes differentially expressed or spliced. Individuals clustered strongly by population for both expression and splicing. Differences at the habitat level were less extensive, but revealed two differentially expressed genes (HSP70 and Gpsm2) and one differentially spliced gene (Cd82) that consistently distinguished roadside and woodland populations. Overall, genetic differentiation between populations was low, suggesting that phenotypic and transcriptomic differences likely emerge in the presence of gene flow and reflect plastic responses. Together, these results highlight transcriptomic plasticity as an important mechanism shaping variation across both development and population differentiation.

Populations along anthropogenic disturbance gradients exhibit phenotypic differences, yet the mechanisms underlying these variations remain unclear. By examining gene expression and alternative splicing in wood frogs, we found significant life stage and population‐specific transcriptomic differences, though only two genes (HSP70 and Gpsm2) showed repeated divergence between roadside and non‐roadside populations. These results suggest that local adaptation and life history trade‐offs in response to road effects may be driven by complex, non‐parallel transcriptomic mechanisms.