Evolution in deep-sea molluscs

University Of Massachusetts Boston, Dorchester MA

Investigators

Abstract

The deep-sea supports one of the most diverse and unique marine communities, the evolutionary and historical development of which are virtually unknown. This research project will contribute very significantly to answering the two most basic questions about evolutionary diversification in this vast environment: Where does it occur, and how? It will also create a solid conceptual and methodological context for future evolutionary studies in the deep sea. In this project, the investigators have developed a deep-sea sampling program to address three main hypotheses about evolution in the deep sea that have emerged from their previous work. 1) The depth differentiation hypothesis suggesting population divergence decreases with depth. 2) The strong break in population structure at 3300 m may represent an unrecognized phylogeographic barrier. 3) Abyssal populations may be sinks that suffer chronic local extinction from being too rare to mate successfully, and are maintained by continued immigration from more abundant bathyal source populations. The investigators will test each of these hypotheses using deep-sea protobranch bivalves and multiple independent loci. Nuclear loci are essential as independent measures of population structure, gene flow and historical influences, but are also critical to establish whether some of the remarkable divergences we have documented represent cryptic species. The primary focus of this project is to collect the samples and develop nuclear markers from those samples that are sufficiently variable in deep-sea protobranchs to test each of the hypotheses and distinguish intra versus interspecific variation. The source-sink hypothesis of abyssal biodiversity is the most synthetic and comprehensive explanation of large-scale patterns of species diversity in the deep ocean. If proven correct by the proposed study of population genetic structure, it will greatly simplify our understanding of both evolutionary and ecological causes of species diversity patterns. Broader impacts of the research program include training for undergraduate and graduate students and public school teachers. UMass-Boston students and faculty have outstanding opportunities to be directly involved in science education and public outreach at all levels. The biology Department has NSF-Research Experiences for Undergraduate and NSF-Undergraduate Mentoring in Environmental Biology grants oriented toward underrepresented minorities. The campus has a Boston Science Partnership Grant to upgrade high school science curricula and a Center of Ocean Science Education Excellence to foster public awareness of ocean science. The research also has broad relevance for conservation and sustainable development of the deep-sea ecosystem. Genetic population structure is a crucial component of biodiversity, and has important implications for extinction potential from deep-sea exploitation.