Speciation across depth gradients in reef corals.

Area of Science:

• Marine Biology
• Evolutionary Genetics
• Ecology

Background:

• Ecological speciation can occur without geographic isolation when traits drive both adaptation and reproductive isolation.
• Light-dependent corals in varying light regimes offer a model for studying speciation.
• Depth-related distributions are observed in coral sister lineages within the photic zone.

Purpose of the Study:

• Investigate the molecular mechanisms of depth-associated adaptive divergence in corals.
• Analyze sequence variation in environmental sensing proteins in depth-segregated coral lineages.
• Identify the role of G-protein-coupled receptors (GPCRs) in coral speciation.

Main Methods:

• Genome-wide analyses of two genetically divergent ecotypes of Orbicella faveolata.
• Analysis of two depth-segregated sister species (O. annularis and O. franksi) with different spawning times.
• Sequencing and variation analysis of proteins involved in environmental sensing.

Main Results:

• Positive selection on G-protein-coupled receptors (GPCRs) drives divergence across depths.
• GPCRs mediate chemo/photo/thermo-reception, facilitating physiological adaptation.
• GPCRs contribute to reproductive isolation through differences in spawning times.

Conclusions:

• Proposes a molecular mechanism for the origin of depth-segregated coral species.
• Ecological divergence can occur at spatial scales smaller than larval dispersal.
• Highlights pathways for generating marine biodiversity through adaptive radiation.