Disease, predation, overfishing, pollution, and climate change have caused a decline in coral populations over the past four decades. Broadcast spawning corals (release gametes into water and fertilization is external) once dominated the Florida reef tract, but since their decline smaller brooding corals (fertilization is internal and larvae are released ready to settle and metamorphose), soft corals, and macroalgae are replacing them. Brooding corals are more resilient to current environmental threats because their larvae are competent to settle almost immediately after release and their reproductive cycle occurs monthly throughout much of the year. Reproductive success in marine invertebrates is often density dependent. Despite the ubiquity of brooders on Florida reefs, much of their reproductive strategy and fertilization success remains unknown. This study examines paternity as a function of colony size and density in Porites astreoides, a common brooding coral in SE Florida. A focal colony of P. astreoides was surrounded by six other colonies, separated from the focal colony at different distances (1m, 7m, and 15m) representing high, moderate, and low population densities, respectively. Each array was replicated three times. The resulting larvae were collected and genotyped with microsatellite markers.
Results/Conclusions
Multiple paternity was seen in each colony and paternity share correlated with distance between colonies and colony size. As distance between colonies increased, there was an increase in self-fertilization. Understanding the fertilization success of these common species is important to effectively assessing and conserving Florida's shifting reef communities.