Spawning Asynchrony and Mixed Reproductive Strategies in a Common Mass Spawning Coral

Area of Science:

• Marine Biology
• Evolutionary Biology
• Genetics

Background:

• Reef-building corals like Platygyra exhibit complex reproductive strategies, with unclear species boundaries.
• Understanding reproductive modes is crucial for evolutionary biology, especially in organisms with varied strategies.

Purpose of the Study:

• To investigate the reproductive modes and genetic structure of Platygyra daedalea at Heron Island, Great Barrier Reef.
• To assess reproductive success and mating patterns during a low-density spawning event.

Main Methods:

• Tagging and sequencing of 18 coral colonies.
• Monitoring spawning events and collecting eggs for fertilization assessment.
• Paternity assignment using genetic data to determine fertilization success and parentage.

Main Results:

• Observed high spawning asynchrony, suggesting distinct genetic clusters within the species.
• Low overall fertilization success (1.5%) with all embryos resulting from self-fertilization.
• Identified two genetically distinct subpopulations with evidence of spatial autocorrelation and inbreeding.

Conclusions:

• Self-fertilization may act as a reproductive assurance mechanism for Platygyra during minor spawning events.
• Coral populations may be more hierarchically structured than previously thought, with smaller breeding units.
• Low-density populations might rely on atypical reproductive modes or require specific conditions for outcrossed fertilization.