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Benthic life stages retain fjord-scale population structure despite pelagic dispersal
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DOI：10.3389/fmars.2026.1895768.png)
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Abstract
En 中文
Understanding how population structure and connectivity emerge in organisms with complex life cycles remains a central challenge in marine ecology; particularly in pelagic systems where dispersal potential is often high. In this study; how life-stage–specific processes shape population structure in the scyphozoan jellyfish Aurelia aurita across a fjord system was investigated. Field observations of benthic polyps and pelagic medusae with population genetic analyses and results from a Lagrangian particle-tracking model were combined to assess connectivity across spatial and temporal scales. Genetic diversity differed between life stages. Benthic polyp populations seemed to maintain consistently high haplotype diversity; whereas pelagic medusa populations showed more spatial and interannual variability. Despite high dispersal potential; genetic structure was spatially heterogeneous within the fjord; with some regions showing persistent diversity and others exhibiting reduced variation. Drift simulations predicted relatively homogeneous mixing but failed partly to reproduce the dominance patterns observed in medusa populations; indicating that hydrodynamic transport alone cannot explain the observed population structure. Instead; the results suggest that connectivity may be shaped by the interaction between dispersal and stage-specific demographic processes. This suggests that the benthic polyp stage can act as a persistent reservoir of genetic diversity; while the short-lived pelagic medusa population represents a transient and environmentally filtered subset of that diversity. Interannual variability further modulates this relationship; with environmental conditions influencing which genotypes are expressed in the pelagic stage in given region. Together; these findings demonstrate that population connectivity in marine organisms with complex life cycles cannot be inferred from dispersal potential alone but emerges from the interplay between life-stage complexity; environmental variability; and local demographic processes.
Keywords:
connectivity
population genetics
spatial structure
benthic–pelagic coupling
bloom dynamics
lifecycle complexity
local retention vs dispersal
scyphozoa
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