Genetic Diversity and Population Dynamics in Marine Mammals

Marine mammals display a remarkable range of genetic diversity shaped by ecological specialisation, historical population fluctuations and human impacts. Genetic diversity underpins the ability of species such as cetaceans and pinnipeds to adapt to changing marine environments, whether through local adaptation to coastal habitats or recovery from severe depletion. Population dynamics—encompassing expansions, contractions and migrations—are revealed by genomic and mitochondrial analyses that trace lineage divergence, admixture and demographic history. Understanding these processes is critical for conservation, as it informs management of isolated or recovering populations, highlights the role of refugial habitats during climatic oscillations and guides interventions to maintain resilience in the face of habitat loss, overhunting and climate change.

Research from Nature Portfolio

Recent genomic investigations of bottlenose dolphins have compared ancient and modern genomes to demonstrate rapid, repeated adaptation to coastal waters. Temporal sampling revealed that alleles associated with coastal ecotypes rose to detectable frequencies soon after habitat emergence, and admixture analyses highlighted a reticulate evolutionary history between pelagic and coastal forms. In the northern elephant seal, whole‐genome sequencing of historical and contemporary individuals has detailed the genomic footprint of an extreme nineteenth‐century hunting‐induced bottleneck. Findings include elevated inbreeding coefficients, increased frequencies of deleterious alleles and impacts on reproductive fitness, yet also a surprisingly swift demographic recovery. Analyses of mitochondrial DNA in Pacific walruses spanning pre‐ and post‐overhunting eras show persistent levels of haplotype diversity, suggesting that high dispersal and lack of strong regional structure have buffered this species against genetic attrition despite dramatic population declines.

Genetic Diversity and Population Dynamics in Marine Mammals publication trend

The graph below shows the total number of articles in genetic diversity and population dynamics in marine mammals across all publications each year (not limited to Nature Index journals).

Technical terms

Genetic diversity: Variation in DNA sequences among individuals within a population, essential for adaptive potential.

Population bottleneck: A sharp reduction in population size causing loss of alleles and reduced genetic variation.

Admixture: The interbreeding of genetically distinct populations, leading to mixed ancestry.

Phylogeography: The study of historical processes governing the geographic distribution of genetic lineages.

Mitochondrial genome: The circular DNA within mitochondria, maternally inherited and widely used for lineage tracing.

Metapopulation: A network of spatially separated populations of a species that exchange individuals and genetic material.

References

1. Ancient dolphin genomes reveal rapid repeated adaptation to coastal waters. Nature Communications (2023).
2. Genomics of post-bottleneck recovery in the northern elephant seal. Nature Ecology & Evolution (2024).
3. Collecting baleen whale blow samples by drone: A minimally intrusive tool for conservation genetics. Molecular Ecology Resources (2024).
4. Fragmented habitat compensates for the adverse effects of genetic bottleneck. Current Biology (2023).
5. Ancient DNA indicates a century of overhunting did not reduce genetic diversity in Pacific Walruses (Odobenus rosmarus divergens). Scientific Reports (2024).
6. Holocene deglaciation drove rapid genetic diversification of Atlantic walrus. Proceedings of the Royal Society B (2023).