Abstract
My dissertation work involves the study of how marine communities develop in the context of local and regional processes. In particular, I am interested in how diversity in a community can be affected through processes such as habitat destruction, community density, and migration, using pen shells and their inhabitants as a model system. In St. Joe Bay, Florida, pen shells (Atrina rigida) are the most abundant source of hard substrate, and the shell provides habitat for approximately 70 species. These communities are discrete habitats that differ from the surrounding seagrass beds and sandy areas. Sixty-six percent of the species found on pen shells are not found in the habitat surrounding pen shells. Pen shells provide shelter for many motile species and hard substrate for settling sessile species and egg-laying fishes. I first demonstrate the role of the pen shell community within sea grass ecosystems. Results suggest that a large component of species found on pen shells are only found with pen shells, and those that are found in the surrounding habitat tend to occur at much lower densities. I then carried out an experiment that showed that the age of the community can affect diversity at local and regional scales. Results also showed that more motile species were more sensitive to these spatial scales, and showed changes in the spatial relationship through time; while for sessile species, the local-regional diversity relationship did not change with succession. In 2003 I performed an experiment that tested successional patterns on pen shells that occurred at high and low densities, as well as a pen shell region that suffered habitat destruction. Local community density did affect local diversity as predicted. Further, motile and sessile species had different responses to habitat destruction. What was interesting from this study is the way individual species responded to different regional sizes. It seems that species’ changes in abundance and distribution (number of shells occupied) differed between the common species and the rare species. The pattern and probability of successful dispersal among habitats can therefore be crucial in determining whether local populations will become rare or increase in abundance. I studied three amphipod species that disperse at different life stages: Neomegamphopus hiatus and Melita nitida disperse as adults, while Bemlos unicornis disperses as juveniles. The metapopulation dynamics of the three species seems highly dependent on the life history stage involved in dispersal.
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