Genetic adaptation despite high gene flow in a range-expanding population

Area of Science:

• Marine ecology and evolutionary biology.
• Population genetics and genomics.
• Environmental adaptation.

Background:

• High gene flow in marine systems can obscure signals of natural selection, hindering the study of genetic adaptation.
• Understanding rapid evolutionary responses is crucial due to environmental changes driving species range expansions.
• Kellet's whelk (Kelletia kelletii) expanded its range significantly, presenting a model for studying adaptation.

Purpose of the Study:

• To investigate genetic adaptation in Kellet's whelk populations from historical and recently expanded ranges.
• To identify genes and genetic markers associated with adaptation to new environments.
• To assess the utility of transcriptomics in understanding marine organismal responses to environmental change.

Main Methods:

• Experimental crosses of Kellet's whelk from distinct ranges (historical and expanded).
• RNA sequencing (RNA-Seq) on offspring reared in a common garden environment.
• Single nucleotide polymorphism (SNP) calling from differentially expressed genes (DEGs) for population assignment.

Main Results:

• Identified 2770 differentially expressed genes between offspring from historical and expanded ranges.
• Achieved high accuracy (92.6%–94.5%) in assigning offspring to their ancestral range using SNPs from DEGs.
• Discovered a significant SNP on triosephosphate isomerase (TPI) with a non-synonymous mutation, upregulated in the expanded range and linked to cold stress response.

Conclusions:

• Experimental transcriptomics can reveal mechanisms of adaptation in marine organisms facing environmental change.
• Identified TPI as a key gene potentially involved in adaptation to the expanded range.
• Demonstrated a novel method for accurately tracking dispersal and gene flow in marine populations.