Asymmetrical gene flow in five co-distributed syngnathids explained by ocean currents and rafting propensity

Area of Science:

• Marine Biology
• Population Genetics
• Oceanography

Background:

• Ocean circulation and macro-algal rafting are key dispersal mechanisms for marine organisms.
• Understanding gene flow directionality and magnitude is crucial for marine population connectivity.

Purpose of the Study:

• To investigate if gene flow direction in seahorses and pipefishes aligns with ocean circulation patterns.
• To determine if species traits predict gene flow magnitude and ocean current influence.

Main Methods:

• Utilized genome-wide single nucleotide polymorphism (SNP) data for population genomic inference.
• Applied coalescent model-based estimates to infer demographic histories and gene flow.
• Integrated ocean circulation data with genetic data for Gulf of Mexico and northwestern Atlantic populations.

Main Results:

• Gene flow directionality in studied syngnathids generally agrees with predicted eastward and northward macro-algal transport via ocean currents.
• The influence of ocean currents on gene flow magnitude is species-specific, depending on rafting propensity and habitat preference.
• Species closely associated with pelagic Sargassum (e.g., Hippocampus erectus) exhibited higher gene flow and stronger directionality compared to nearshore species.

Conclusions:

• Ocean circulation plays a significant role in shaping marine population structure and genetic diversity.
• Species-specific traits, particularly habitat association with macro-algae, mediate the impact of ocean currents on dispersal patterns.
• Combining population genomics with oceanographic data provides valuable insights into marine dispersal dynamics.