Morphology and evolution of the coral genera, Anomocora, Asterosmilia, and Montastraea from the Neogene to the Recent in the Caribbean.

摘要

For this dissertation, I studied patterns of change in azooxanthellate corals from the Late Neogene to the Recent in the Caribbean and their association with the closure of the Central American Isthmus.; For Chapters 1 and 2, I studied the morphology and evolution of two closely related azooxanthellate coral genera Anomocora and Asterosmilia. I reconstructed the phylogenetic relationships between and within these two genera using both continuous and discrete characters. Characters related to corallum and calicular shape seem most important in distinguishing between the genera Anomocora and Asterosmilia and characters related to size seem to be most important in distinguishing species within each genus. Evolutionary change in these genera appears to be related to environmental change. Using morphometric methods, I examined three species of Asterosmilia from Late Neogene of Central America in more detail. Two of the three species were morphologically stable for two million years with change and speciation after closure of the Central American Isthmus.; For Chapters 3 and 4, I examined the biogeography and diversity of azooxanthellate corals from the Late Neogene until the Recent in the Caribbean. During the Neogene, there were island and continental azooxanthellate coral provinces in the Caribbean. These two provinces still exist despite the fact that there was turnover between 4 and 1 Ma in which speciation was higher than extinction. During the last two million years, increased nutrients and fluctuating temperatures during Northern Hemisphere glaciation may have had an adverse affect on zooxanthellate corals due to their symbiotic algae. However, other groups such as the mollusks and azooxanthellate corals might have flourished under these conditions.; In Chapter 5, I outline a new method of quantifying the "bumpiness" in colony shape for the Montastraea annularis sibling species complex. I first modeled a smooth coral using nonlinear least squares method and compared the height of corallites between the model and the original coral. I next analyzed the spatial variation of this measurement using variograms. I also examined the relative compactness of the corallites for spatial variation. This method is promising with visible differences between the species in the Montastraea annularis complex.