de Vargas The surface layers of Earth's oceans are largely dominated by unicellular organisms that play fundamental roles in global biogeochemical cycles. The most successful groups of marine planktonic protists can build micro-skeletons that are remarkably preserved in kilometers-thick layers of deep-sea sediments, representing a unique archive for the study of paleo-climate, stratigraphy and evolution. However, studies of their biology and evolution at the species and population levels have been hindered by the huge dimension and extremely fast-changing conditions of their oceanic habitat, as well as the relative absence of morphological characters for species recognition. The conventional paradigm is that the microplankton is composed of a limited number of morphologically distinct species, each with broad ecological tolerances and transoceanic distribution. Preliminary molecular data have challenged this model and promoted the hypothesis that all conventional morphological species are in fact clusters of a few sibling species, which may have diverged several million years ago but are separated by only subtle morphological characters. Drs. De Vargas and Aubry and their colleagues will examine global biodiversity and evolutionary patterns underlying the origin and maintenance of species in the oceanic phytoplankton group of coccolithophores. Innovative approaches combining advanced molecular and microscopy methods will allow gathering genetic and morphological information at the single-cell level from numerous near-shore and open ocean stations across the Pacific, Atlantic and Indian Oceans. The data will allow reconstructing the evolutionary history of the coccolithophores, defining boundaries between species, and recognizing their ecological niches in the three-dimensions of the global ocean. Molecular clocks calibrated against the excellent coccolithophore fossil record will be used to estimate the divergence times of the sibling species within a morphological "species". The characters of the skeleton that permit recognition of the genetic species will be stratigraphically tracked within well-preserved sediment cores, allowing their geological first appearance to be compared to the molecular-age estimates. This research, incorporating systematic biology, paleontology, and oceanography, will create a variety of broad scientific and societal impacts. By analyzing the time scale and ecological factors controlling diversity dynamics in the ocean, this project will help to predict how pelagic biodiversity may react to the increasingly severe climatic changes projected in the near future. The project will provide essential taxonomic, genetic, and ecological data to the scientific community using the micro-skeletons of marine protists as routine tools to analyze past oceanic and climatic changes. The project will involve an intense education effort serving K-12 students, educators, and large public audience through a collaborative work with the education staff at Rutgers University and a new website. It will directly involve undergraduate and graduate students through different programs at Rutgers University and the international partner Institutes.
