Coral Reef Project—Papers in Memory of Dr. Thomas F. Goreau. 14.

The Ecology of Molluscs of Thalassia Communities, Jamaica, West Indies. I. Distribution, Environmental Physiology, and Ecology of Common Shallow-Water Species

Infaunal and semi-infaunal bivalves were collected from Thalassia environments 1 m deep or shallower at 23 localities in Florida, Jamaica, Panama, and Puerto Rico. The lucinacean families Lucinidae and Ungulinidae dominate the faunas and comprise five of the six most abundant species. These bivalves exhibit a broadly adapted strategy. They are locally and regionally abundant and occur in a variety of environments in addition to beds of Thalassia shallower than 1 m. Experiments and field data show these species are tolerant of a wide range of temperature, salinity, and stagnation. Some Lucinidae possess respiratory pigments, which are uncommon among the Bivalvia. All six species inhabit a wide range of sedimentary conditions. Morphological evidence suggests that the Lucinidae can process a greater size range of food particles than can most Bivalvia. Species from deeper Thalassia environments are apparently excluded from areas shallower than 1 m by extreme variations in environmental conditions. However, the six most abundant species from areas of Thalassia shallower than 1 m are not competitively excluded from deeper environments by more specialized taxa, as would be predicted by the stability-time hypothesis. Significant correlation between the frequency of occurrence of these six species at 30 Caribbean localities and their average physiological tolerance rank suggests that variations in physiological tolerance, rather than competition, are of primary importance in limiting the distributions of dominant bivalve species within these shallow-water Thalassia environments.