Abstract
The Antarctic was once considered isolated and one of the most stable ecosystems on Earth, but with climate change, it is facing challenges, including invasive species, shifting ocean circulation patterns, warm waters, and melting sea ice, all of which make it highly vulnerable. The species in this region, faced with climate change, have few options – if they cannot cope with the changes, they must undergo range shifts or extirpation/extinction. Understanding all these processes and changes requires insights into population structure to infer individual movement and gene flow among populations.
The Ross Sea is home to one of the world's largest marine protected areas, and the effectiveness of this protected area depends on dispersal and colonization patterns between protected and non-protected regions. Despite the importance of population genetics research in conservation biology, many taxa in the Ross Sea remain understudied.
I investigated population connectivity processes across different taxa in this region. I addressed the following research questions:
1. Is there population structure at fine and coarse scales in the Ross Sea Region?
2. Does population structure indicate barriers to gene flow, or patterns of genetic connectivity?
3. What are the likely environmental and geological drivers (e.g., ocean currents, depth, glacial periods) of population structure?
4. How do life-history traits influence population structure at both fine and broad spatial scales?
For answering these questions, I employed three 'model taxon' systems: host-parasite, fish, and echinoderms. I used single-nucleotide polymorphism (SNP) data generated by Genotyping-by-Sequencing (GBS) on 510 samples, including 314 fish, 123 echinoderms, and 73 parasites. Almost all these model taxa have long larval stages, long life spans, and unique physiological characteristics that enable them to adapt to near-freezing waters; however, population genetic analyses revealed mosaic patterns among these taxa.
In the first system, I assessed a host-parasite pair to compare population structures. The results showed that the population genetic structure of host and parasite across the Ross Sea differs considerably. From the results, I inferred how contrasting life histories and dispersal strategies are likely to have shaped the observed genetic patterns.
In the second system, involving five fish species, I found specific scenarios for each species' population genetic structure. Connectivity patterns ranged from strong population differentiation to near panmixia. These results demonstrated that common predictors such as larval duration or generation time alone cannot explain genetic structure; instead, depth, dispersal potential, and ecological adaptations were more influential. In the third system, I investigated two echinoderm species: Odontaster validus (a sea star) and Sterechinus neumayeri (a sea urchin), which typically lack active dispersal during adulthood. The genomic signatures observed in these species revealed a strong impact of both historical and contemporary processes. For the sea star, patterns of genetic variation indicated historical population expansions followed by periods of restricted connectivity, consistent with survival in glacial refugia during past climatic fluctuations. Sea urchins, on the other hand, showed signs of more consistent connectivity, though with localized differentiation that may reflect habitat specificity and contemporary current-driven larval dispersal.
Together, these results emphasized that even among taxa with similar dispersal potential, evolutionary paths may differ depending on their demographic histories, larval ecology, and sensitivity to environmental barriers.
This study contributes to the Antarctic Science Platform by projecting Ross Sea ecosystem changes in a warming world, providing critical genomic baselines for assessing how biodiversity may respond to future climate-driven changes. Importantly, the results emphasize the need to incorporate connectivity into marine spatial scheduling to ensure that MPAs remain effective conservation tools under ongoing environmental change.