EVIDENCE FOR RESTRICTED GENE FLOW IN THE VIVIPAROUS CORAL SERIATOPORA HYSTRIX ON AUSTRALIA'S GREAT BARRIER REEF

The commonly observed high diversity of trees in tropical rain forests and corals on tropical reefs is a nonequilibrium state which, if not disturbed further, will progress toward a low-diversity equilibrium community. This may not happen if gradual changes in climate favor different species. If equilibrium is reached, a lesser degree of diversity may be sustained by niche diversification or by a compensatory mortality that favors inferior competitors. However, tropical forests and reefs are subject to severe disturbances often enough that equilibrium may never be attained.

Synchronous multispecific spawning by a total of 32 coral species occurred a few nights after late spring full moons in 1981 and 1982 at three locations on the Great Barrier Reef, Australia. The data invalidate the generalization that most corals have internally fertilized, brooded planula larvae. In every species observed, gametes were released; external fertilization and development then followed. The developmental rates of externally fertilized eggs and longevities of planulae indicate that planulae may be dispersed between reefs.