GENETIC CONNECTIVITY OF OCTOCORALLIA ACROSS ABIOTIC GRADIENTS IN THE DEEP GULF OF MEXICO

Abstract

Cold-water corals increase habitat heterogeneity and enhance biodiversity in deep waters worldwide. Despite the recognition of their importance in the deep sea, limited data exist on the ecology and evolution of deep-water corals. The overarching goal of this dissertation research was to integrate molecular, morphological, and ecological data to understand the degree to which populations are connected, species are distributed, and communities are assembled in the deep (250-2500 m) Gulf of Mexico (GoM). Specifically, several hypotheses were tested regarding the roles of environmental variables, particularly depth, influencing population and community structure. Combining phylogenetic and population genetic approaches with ecological data enabled species delimitations of many taxa while demonstrating that deep-water populations and communities diverge over short bathymetric distances. It appears that population isolation, congeneric species replacement and changes in community composition occur rapidly with depth, and these changes are likely due to a combination of both dispersal limitation and adaptive divergence with depth. Local self-recruitment may also be strong within any one site. Furthermore, results suggest that evolutionary history and neutral dynamics play a critical role in octocoral community assembly in the deep sea. This dissertation not only contributes a substantial amount of evolutionary and ecological information on a poorly studied group of foundation species in the deep sea, this research has broader implications for aiding in efforts to protect these long-lived, foundation species from anthropogenic disturbances.