The Hardy-Weinberg Equilibrium model was used as a platform for analyzing a field survey data on the distribution of mangrove species in two is lets of Eastern Visayas, Tabuk and Cabgan. The study is part of a larger Island Biodiversity program of the Cebu Normal University. A new estimator, developed by the first author, for measuring deviations from equilibrium was used in the study, while the relationship between the classical Shannon’s diversity index and the Hardy-Weinberg equilibrium was likewise explored. Results revealed that the probability of extinction of the mangrove species in both islands are relatively high and the most probable future configuration of these species, apart from a total extinction scenario, is either a single-species ora two-species configuration. The protection of the Tabuk islet yielded positive benefits for the diversity of the mangrove species, while a reforestation project for the two islands served to reduce heterogeneity viz. reduce diversity, because only one or two species of mangroves were planted in the early part of 2000.