Genetic Structure and Gene Flow in Aquatic Species

Throughout aquatic ecosystems, genetic structure and gene flow underpin the capacity of populations to adapt to environmental change and maintain resilience. Genetic structure emerges from the interplay of historical processes, such as glacial colonisation, and contemporary influences, including habitat fragmentation, water currents and human-mediated translocations. In riverine and marine settings alike, dispersal barriers—whether natural, such as waterfalls and oceanic fronts, or anthropogenic, such as dams and weirs—shape patterns of connectivity among populations. High-resolution molecular markers, ranging from microsatellites to genome-wide single nucleotide polymorphisms, have revealed fine-scale and broad-scale structuring that often contrasts between mitochondrial and nuclear genomes, reflecting sex-biased dispersal or founder events. Asymmetric gene flow driven by directional water movement further complicates conventional measures of connectivity, necessitating novel analytical frameworks. Insights from model taxa, such as lampreys, amphipods and molluscs, illustrate how life-history traits and ecological barriers interact to produce divergent genetic landscapes. Understanding these dynamics is critical for conservation management, guiding the design of protected areas, the prioritisation of restoration efforts and the detection of invasive pathways. By integrating genomic tools with hydrodynamic models and long-term monitoring, researchers can now map genetic corridors, forecast the impacts of barrier removal, and inform policy across freshwater and marine realms.

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Genetic Structure and Gene Flow in Aquatic Species publication trend

The graph below shows the total number of articles in genetic structure and gene flow in aquatic species across all publications each year (not limited to Nature Index journals).

Technical terms

Genetic structure: The spatial distribution of genetic variation within and among populations.

Gene flow: The transfer of genetic material between populations through migration or dispersal.

Microsatellite: A short, tandemly repeated DNA sequence used as a highly polymorphic genetic marker.

Single nucleotide polymorphism (SNP): A single base-pair variation in the DNA sequence across individuals.

Restriction-site-associated DNA (RAD) sequencing: A genotyping method that identifies and scores SNPs at consistent positions throughout the genome.

Asymmetric gene flow: Unequal rates of gene exchange between pairs of populations, often reflecting directional dispersal forces.

References

1. Contrasting population genetic structure among freshwater‐resident and anadromous lampreys: the role of demographic history, differential dispersal and anthropogenic barriers to movement. Molecular Ecology (2015).
2. Individual small in‐stream barriers contribute little to strong local population genetic structure five strictly aquatic macroinvertebrate taxa. Ecology and Evolution (2022).
3. Directional genetic differentiation and relative migration. Ecology and Evolution (2016).