Mitochondrial and nuclear DNA analyses reveal fine scale geographic structure in bottlenose dolphins (Tursiops truncatus) in the Gulf of Mexico

Abstract

There is a need for biological information to support current stock designations of bottlenose dolphins (Tursiops truncatus) in the Gulf of Mexico. The existence of many inshore, resident ''communities'' raises questions as to the relationship these dolphins may hold with dolphins inhabiting neighboring inshore and coastal areas. In this study, population subdivision was examined among four resident, inshore bottlenose dolphin stocks (Sarasota Bay, FL, Tampa Bay, FL, Charlotte Harbor, FL and Matagorda Bay, TX) and one coastal stock (1-12 km offshore) in the Gulf of Mexico. Evidence of significant population structure among all areas was found on the basis of both mitochondrial DNA (mtDNA) control region sequence data and nine nuclear microsatellite loci. Estimates of relatedness showed no population contained a significantly high number of related individuals, while separate AMOVAs for males and females indicated that both sexes exhibit a significant level of site philopatry. Results presented here provide the first genetic evidence of population subdivision between the coastal Gulf of Mexico and adjacent inshore areas along the central west coast of Florida. Such strong genetic subdivision is surprising given the short geographical distance between many of these areas and the lack of obvious geographic barriers to prevent gene flow. These findings support the current, separate identification of stocks for bottlenose dolphins inhabiting the eastern coastal and inshore areas of the Gulf of Mexico.

Survival, density, and abundance of common bottlenose dolphins in Barataria Bay (USA) following the Deepwater Horizon oil spill

“…Fazioli et al (2006) found some interaction between coastal and estuarine dolphins on the west coast of Florida, but no long-term immigration to inshore areas. Sellas et al (2005) used genetic data to show that coastal and estuarine populations off Florida are demographically independent. Given foraging specialties, we theorize that dolphins from coastal populations near Barataria Bay were unlikely to immigrate into an estuarine environment due to significant differences in habitat and prey types.…”

Live-captures of common bottlenose dolphins Tursiops truncatus and unassessed bycatch in Cuban waters: evidence of sustainability found wanting

“…Further, microsatellite and mtDNA sequence variation Mead and Potter (1995). A high degree of long-term site fidelity and population structuring has been documented over the past 36 years along the central west coast of Florida, including bays, sounds, estuaries, and adjacent Gulf of Mexico coastal waters, based on behavioural and genetic studies (Irvine et al, 1981;Wells et al, 1987;Scott et al, 1990;Duffield and Wells, 1991;Wells, 1991Wells, , 2003Sellas et al 2005).…”

High gene flow in oceanic bottlenose dolphins (Tursiops truncatus) of the North Atlantic

“…In the Gulf of California, a distribution break is found around the 60m-isobath (Segura et al 2006). At a regional scale, genetic analyses evidenced differentiation between the eastern and western basins of the Mediterranean Sea (Natoli et al 2005), as well as between coastal populations of the Gulf of Mexico (Sellas et al 2005) and the Northern Bahamas (Parsons et al 2006). Despite the broad geographic coverage of all these studies, bottlenose dolphins have only been studied in peri-continental areas, and virtually nothing is known about distant offshore regions.…”