Ecology & Evolutionary Biology
Earth & Marine Sciences A308
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ROBERT C. VRIJENHOEK Adjunct Professor of EE Biology Senior Scientist, Monterey Bay Aquarium Research Institute BA University of Massachusetts, Amherst PhD University of Connecticut, Storrs MBARI Easter Microplate Expedition Fiji/Lau Expedition

Monterey Bay Aquarium Research Institute 7700 Sandholdt Road Moss Landing, CA 95039 Phone: (831) 775-1799 Fax: (831) 775-1620 vrijen@mbari.org office hours

Marine Biology, Genetics and Evolution, Conservation

Our molecular ecology research group studies the ecological and evolutionary consequences of genetic diversity in natural populations of marine and aquatic animals. Recently we have focused on gene flow and evolutionary relationships of animals found in deep-sea hydrothermal vents and cold water seeps. Most vent invertebrates have effective modes of dispersal that maintain genetic continuity among populations distributed across thousands of kilometers along mid-ocean ridge systems. For some organisms, however, structural aspects of the ridge system (large transform faults, microplates, and other discontinuities) correspond with restricted gene flow, geographical isolation, or recent speciation events. We have also generated molecular phylogenies for several of the dominant invertebrate taxa found at vents and seeps. New species of mussels, clams, annelids, and crabs have been discovered and described. To date, our studies of these organisms suggest the dominant fauna of hydrothermal vents had relatively recent origins during the last 100 million years. In addition, we are interested in the modes of transmission and patterns of evolution of the bacterial endosymbionts associated with many vent invertebrates.  Vesicomyid clams and their vertically transmitted endosymbionts exhibit parallel phylogenetic patterns (co-speciation) that suggest a tight co-evolutionary relationship. In contrast, vestimentiferan tubeworms and their horizontally transmitted endosymbionts do not exhibit co-speciation.

We recently discovered two new species of tube-dwelling worms that live on the bones of dead whales. Females of these mouthless, gutless worms (genus Osedax) grow complex roots that invade the bone marrow contain. Symbiotic bacteria in the roots extract nutrients from the whale bone and transmit nutrients to the worms. Osedax males are microscopic and live in the gelatinous tubes of females. Sex ratios are highly skewed with more than 25 males living in an average female's tube. Sex appears to be environmentally determined.

We also engage in a long-term collaboration with the Scholin lab at MBARI  to develop molecular markers for the in situ detection of larval marine invertebrates. DNA capture probes, bound to membranes, hybridize with nucleic acids extracted from the water column to form duplexes that can be detected with chemiluminescent probes. We can presently detect microscopic barnacle and mussel larvae, and we are developing probes for the detection of larvae of alien species that have invaded the Monterey and San Francisco Bays. We are also developing probes to detect the larvae of deep-sea vent and cold-seep worms and mollusks.

Research efforts during the past 30 years have focused on the evolutionary and ecological consequences of sexual and asexual reproduction in Mexican live-bearing fish of the genus Poeciliopsis. We use a variety of molecular approaches to contrast gene and genomic evolution under the recombinant and non-recombinant breeding systems found in these fish. Sexual species of Poeciliopsis also served as a model system for conservation studies. Field and experimental studies have shown that the competitive ability, disease resistance, developmental stability, growth rate, and fecundity of these fish may be compromised by losses of genetic diversity that accompany population bottlenecks, founder events, and inbreeding.

Selected Publications

Goffredi SK, Orphan VJ, Rouse GW, et al. (2005) Evolutionary innovation: A bone-eating marine symbiosis. Environmental Microbiology, in press.

Rouse GW, Goffredi SK, Vrijenhoek RC (2004) Osedax: Bone-Eating Marine Worms with Dwarf Males. Science 305: 668-671.

Hurtado LA, Lutz RA, Vrijenhoek RC (2004) Distinct patterns of genetic differentiation among annelids of eastern pacific hydrothermal vents. Molecular Ecology: 13: 2603-2615

Little CTS, Vrijenhoek RC (2003) Are hydrothermal vent animals living fossils? Trends in Ecology and Evolution 18: 582-588

Won Y-J, Hallam SJ, O'Mullan GD, Pan IL, Buck KR, Vrijenhoek RC (2003) Environmental acquisition of thiotrophic endosymbionts by deep-sea mussels of the genus Bathymodiolus. Applied and Environmental Microbiology 69: 6785-6792

Won Y, Young CR, Lutz RA, Vrijenhoek RC (2003) Dispersal barriers and isolation among deep-sea mussel populations (Mytilidae: Bathymodiolus) from eastern Pacific hydrothermal vents. Molecular Ecology 12: 169-184

Van Dover CL, German CR, Speer KG, Parson LM, Vrijenhoek RC (2002) Evolution and biogeography of deep-sea vent and seep invertebrates. Science 295, 1253-1257.

Mateos M, Sanjur OI, Vrijenhoek RC (2002) Historical biogeography of the livebearing fish genus Poeciliopsis (Poeciliidae: Cyprinodontiformes). Evolution 56, 972-984.

Vrijenhoek, R. C., 1998 Animal clones and diversity. Bioscience 48: 617-628.

Vrijenhoek, R. C., 1998 Conservation genetics of freshwater fish. Journal of Fish Biology 53 (Supplement A): 394-412.