The Antarctic Circumpolar Current as a diversification trigger for deep-sea octocorals

Area of Science:

• Marine Biology
• Oceanography
• Genetics

Background:

• The Antarctic Circumpolar Current (ACC) is a major ocean current influencing deep-sea ecosystems.
• Deep-sea population connectivity across the ACC is poorly understood.
• Bottleshrush octocorals (Primnoidae) were used to investigate ACC's effect on brooding species.

Purpose of the Study:

• To assess the Antarctic Circumpolar Current (ACC) as a barrier to gene flow in deep-sea octocorals.
• To determine if octocoral diversification correlates with the ACC's origin.
• To analyze phylogeographic patterns in the South Pacific and Southern Ocean.

Main Methods:

• DNA sequencing of two nuclear genes from 80 individuals.
• Phylogeographic model-testing approaches.
• Divergence time analyses.

Main Results:

• A significant phylogenetic break was identified, corresponding to the ACC's location.
• Substantial genetic structure was found among four regional populations.
• Shared haplotypes indicated long-distance, asymmetrical migration.
• Population separation occurred in the Middle Miocene, post-ACC formation.

Conclusions:

• The ACC functions as a semi-permeable barrier, structuring populations while allowing limited gene flow.
• Miocene fluctuations in ACC positioning likely drove octocoral diversification.
• Evidence suggests distinct species may exist within the sampled octocoral populations.