ABSTRACT
Diadema antillarum populations throughout the Caribbean suffered mass mortality in 1983. Panamanian populations for which pre-mortality population density and population genetic data existed have been monitored continuously over the past ten years to determine their abundance, rate of recruitment and genetic variability. Levels of recruitment over this period have been very low; population density has remained at less than 10% of pre-mortality levels. However, despite this bottleneck in population size, genetic variability is as high as it has always been. Observed changes in gene frequencies have been minor and very similar to those of Echinometra lucunter and E. viridis, two species that did not undergo any mass mortality. Other species of echinoids, believed from pre-mortality small-scale experiments to be competing with D. antillarum, did not increase their population density. Algal cover, reported to have undergone dramatic increases in other areas of the Caribbean, has not displayed a similar response in Panama, possibly because of the presence of dense populations of herbivorous fish. Known predators of D. antillarum have switched diets, but have shown no numerical response to the demise of their preferred pray. Overall, the impact of the mortality of D. antillarum on the Panamanian reef communities has been small.
