Increased clonality and genetic differentiation across the Arctic Ocean in tetraploid sea anemone Aulactinia stella
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Abstract
Reproductive mode is a key factor shaping genetic diversity, evolutionary potential, and the processes of dispersal and colonization. Clonality is particularly common in harsh environments and at the margins of species ranges, where it supports persistence, enables rapid growth, and promotes the maintenance of locally adapted genotypes. In the rapidly changing Arctic, increasing ecological connectivity is eroding historical barriers for sessile species. Evaluating genetic diversity in this context, before global change further alters Arctic ocean, is essential for understanding evolutionary dynamics during range expansion and for informing conservation strategies. Aulactinia stella is a circumpolar sea anemone with physiological characteristics in laboratory conditions suggesting a potential for clonal reproduction. In this study, we investigated its reproductive modes in natural populations across the Arctic ocean, from the northern Pacific to the Atlantic, and examined how genetic diversity is structured between adults and juveniles at five sampled sites. Across all study sites, we observed only females or individuals lacking gonads, with the exception of Kamchatka, where males were also present. Genetic indices and changes in genotype frequencies between adults and juveniles confirmed that this species reproduces partially by parthenogenesis. Populations on the Atlantic side were highly clonal with clonal rates ( c ) estimated at 80-99%, whereas populations on the Pacific side reproduced more sexually (c around 50%). Allelic diversity was twice as high in Kamchatka and Kuril populations, suggesting North Pacific coasts being the main last glacial refugia of A. stella . We found a stepping-stone pattern of genetic structure from Kamchatka to Atlantic populations, consistent with contemporary ocean currents and melted summer sea ice. Only a subset of the juvenile genetic diversity, mostly of local origin, was found in the established adults, while juveniles exhibited lower levels of genetic differentiation across the Arctic Ocean. Our findings underscore the need for further ecological and behavioral investigations to elucidate the mechanisms allowing the current possibilities of dispersal of this species across the Arctic Ocean.
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This study provides an interesting contribution to our understanding of reproductive strategies and genetic diversity in Arctic marine invertebrates.
The authors investigate the reproductive modes of the circumpolar sea anemone Aulactinia stella across a broad geographic range, from the northern Pacific to the Atlantic, combining population genetic analyses with observations of reproductive structures. Their results reveal a geographic pattern in reproductive strategies, with predominantly clonal populations in the Atlantic and more sexually reproducing populations in the Pacific. The identification of parthenogenesis as a reproductive mode in A. stella, along with strong clonality in several Arctic populations, has important implications for understanding how sessile organisms persist and disperse in extreme and rapidly changing …
This study provides an interesting contribution to our understanding of reproductive strategies and genetic diversity in Arctic marine invertebrates.
The authors investigate the reproductive modes of the circumpolar sea anemone Aulactinia stella across a broad geographic range, from the northern Pacific to the Atlantic, combining population genetic analyses with observations of reproductive structures. Their results reveal a geographic pattern in reproductive strategies, with predominantly clonal populations in the Atlantic and more sexually reproducing populations in the Pacific. The identification of parthenogenesis as a reproductive mode in A. stella, along with strong clonality in several Arctic populations, has important implications for understanding how sessile organisms persist and disperse in extreme and rapidly changing environments.
The strength of this work lies in the extensive sampling carried out across the entire range of the species. The study also has some limitations, which are adequately discussed in the text, mainly the use of microsatellites that may display mutational patterns difficult to interpret (Ellegren, 2004).
Overall, this work is methodologically sound, clearly presented, and provides valuable data for understanding the evolution and connectivity of Arctic species. It will be of broad interest to researchers studying reproductive evolution, population genetics, and biogeography in polar ecosystems.
References
Ekaterina Bocharova, Alexander Volkov, Solenn Stoeckel (2025) Increased clonality, decreased allele diversity and high genetic structure in tetraploid sea anemone Aulactinia stella populations from North Pacific to Atlantic across the Arctic Ocean. bioRxiv, ver.3 peer-reviewed and recommended by PCI Evolutionary Biology https://doi.org/10.1101/2025.04.24.650399
Ellegren, H. (2004) Microsatellites: simple sequences with complex evolution. Nature Reviews Genetics, 5, 435–445. https://doi.org/10.1038/nrg1348
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