Population Structure of Common Bottlenose Dolphins in Coastal and Offshore Waters of the Gulf of Mexico Revealed by Genetic and Environmental Analysis

The common bottlenose dolphin (Tursiops truncatus ) is one of the most well-recognized and abundant marine mammals within the Gulf of Mexico (GOMx). However, there is still much that is not understood about the population structure, ecology, and habitat use of this species in these waters. An extensive review of previous GOMx research focusing on general biology and ecological characteristics, potential threats, population genetic studies, and management strategies for bottlenose dolphins was conducted. This review revealed that little is currently known about dolphins living in coastal and offshore waters of the GOMx. Five management stocks have been delineated in coastal and offshore waters based on assumptions of differential habitat use, but these assumptions have never been tested and these stocks may not represent biological populations. To address this issue, I examined genetic population structure of bottlenose dolphins in coastal and offshore waters of the GOMx using three different molecular markers: mitochondrial DNA, microsatellites, and novel single nucleotide polymorphisms (SNPs). SNPs are a relatively new molecular tool but have only recently been used for studies on non-model organisms and have never been developed for use with bottlenose dolphins. Using both novel and previously published primer sets, I screened the bottlenose dolphin genome and identified and characterized 53 SNP loci for use in population genetic studies on bottlenose dolphins. Analysis of 52 SNPs, 19 microsatellite loci, and 354 base pairs of the mitochondrial DNA control region identified seven genetically-distinct populations in coastal and offshore waters of the GOMx. These seven populations do not correspond to the five current management stocks, suggesting some revision is necessary. In order to further investigate the role that environmental characteristics play in maintaining the differentiation among populations, canonical correspondence analysis was performed on data from numerous environmental variables. Analysis results revealed that variation in depth and slope correlate well with the occurrence of the seven dolphin populations. Taken together, this research provides new data on population structure for bottlenose dolphins that will aid future management and conservation of the true biological populations of bottlenose dolphins that exist in the GOMx.