EVALUATING FUNCTIONAL DIVERSITY OF MARINE MOLLUSK COMMUNITIES: A CASE STUDY OF GRAND CAYMAN ISLAND

The application of diversity measures as a tool for monitoring biotic community health has extensive use in conservation science. Traditional measures of ecosystem health are calculated using taxonomic diversity. While these measures provide important insights into community organization by assessing species richness, evenness, and ranked abundance, they fall short when assessing the functional relationships of individuals within or among species. Without a clear understanding of the roles filled by taxa within a community, and how these taxa interact with each other, it is challenging to predict changes in a community as a result of perturbation. Assessment of functional diversity based on a thorough understanding of the biological roles of the species present allows for more predictive and targeted conservation efforts. This study aims to construct and test a functional diversity framework using a collection of shallow-dwelling marine mollusks from Grand Cayman Island as a method of determining this community’s overall health and resilience to past and future perturbations.

To establish the functional groups, 11 life mode variables, including: feeding strategy; shell composition; tiering; motility; salinity, depth, substrate, and temperature preference; body size; geographic range area, and fossil first appearance data were determined for each identified taxa in the dataset. Attributes were recorded using a fuzzy coding method, in which species could reflect a value of “3” (obligatory), “0” (no expression), “1” or “2” (facultative expression). We then used R to calculate a cluster analysis based on Gower distances among all species present based on the fuzzy coded matrix. Individual clusters were established using a bootstrapping method to determine their statistical significance. Preliminary results using this method indicate the formation of ~20 functional groups, and testing will be applied to reveal which functional variables are strongly associated with different functional groups. Further analysis aims to apply our functional framework to species abundance data and quantify important markers like functional redundancy to assess the health of this molluscan community.