"And it is an interesting biological fact that all of us have, in our veins the exact same percentage of salt in our blood that exists in the ocean, and, therefore, we have salt in our blood, in our sweat, in our tears. We are tied to the ocean. And when we go back to the sea, whether it is to sail or to watch it we are going back from whence we came."
-John F. Kennedy, September 14th 1962
The Vesicomyidae or
Giant deep-sea clams
My research has focused on a sub-family of deep-sea clams; the Vesicomyidae. These clams live at deep-sea reducing habitats where chemosynthetic bacteria support a vibrant host of animals. The most famous of the deep-sea reducing habitats is the hydrothermal vent. Other types of reducing habitats include cold-seeps and whale falls.
Vesicomyid clams host endosymbiotic chemosynthetic bacteria in their gills. These bacteria convert chemical energy from sulfide into energy the clams can use. These clams live at reducing environments as deep as 9,000 meters (5.6 miles) and are found in every ocean basin.
Who evolved from whom and when?
Phylogenetics is the study of evolutionary histories and relationships among individuals or groups of organisms using genetic data. This type of study is important in the deep-sea where new species are constantly discovered, sample numbers are typically small and cryptic species are abundant.
During our expeditions in the Atlantic Inter-American Sea we sampled two species of clams: Abyssogena southwardae and a newly discovered clam from the Barbados Accretionary Ridge. Using mitochondrial COI sequences we discovered that these two species have different evolutionary histories in the Atlantic Ocean. The widespread A. southwardae colonized the Atlantic from a Pacific ancestor relatively recently (about 1 million years ago). Conversely the newly discovered species only described from one site is relatively old—it likely diverged from a common ancestor in the Pacific when the Isthmus of Panama closed at least 2.8 million years ago.
Studying the evolutionary history of deep-sea organisms can help reveal how they have adapted to the deep-sea, how new species emerge and how long the deep-sea has been colonized by these species.
Population Genetics or
Who is related to whom, how closely and why?
Population genetics is the study of populations from (typically) one species of organism. We ask questions such as: Which populations are most closely related? How closely related are two distant populations compared to nearby populations. Why are there blocks/avenues of gene flow?
My research is focused on populations of the deep-sea clam A. southwardae. These populations are spread across the Atlantic Ocean and include vents and seeps in the Gulf of Mexico, Barbados Accretionary Ridge, Mid-Atlantic Ridge and the Lobes of Congo. My research addresses how frequently does gene flow occur between these populations. Preliminary work suggests that trans-Atlantic gene flow occurs rarely if at all. Gene flow between nearby regions also occurs at low frequency. High levels of gene flow only occur within regions, such as between the populations in the Barbados Accretionary Ridge.