The Phylogeny and Evolution of Cetacea: Resolution of Rapid Radiations and a Molecular Blueprint for Modern Whales, Dolphins, and Porpoises

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The evolutionary origin of Cetacea (whales, dolphins, and porpoises) in the Eocene, 50 million years ago, ranks among the best-documented macroevolutionary transitions. To non-scientists, this move from a terrestrial habitat to a committed aquatic lifestyle might seem improbable, yet the wholesale changes in anatomy required for this transformation are recorded in the fossil record. With the advent of genomics, it is now possible to study this remarkable evolutionary change at the molecular level. In this project, researchers will document the genetic basis of traits that were altered in the evolutionary genesis of these secondarily aquatic mammals and trace the molecular changes that produced a modern whale. In this project, researchers will train a postdoctoral scholar, graduate students, and multiple undergraduate interns at UC Riverside, a minority serving institution. The ethnically diverse makeup of UC Riverside provides an opportunity to bring cutting edge research to students who are historically underrepresented in science. Results from the research also will be incorporated into coursework and provide content for museum displays focused on evolutionary principles. Grant participants, including students, will collaborate with staff at the San Diego Natural History Museum to relate exciting research breakthroughs in a revitalized 'Fossil Mysteries' exhibit with bilingual educational modules.For Cetacea, standard phylogenetic analyses of fossil and molecular data have been used to reconstruct major phenotypic transformations in the group, with fossils providing signposts that place key evolutionary innovations relative to Earth history. Yet, despite ongoing phylogenetic studies based on large datasets, a fully resolved reconstruction of cetacean evolution has been elusive. The researchers propose a three-pronged approach to an enhanced study of cetacean evolutionary history that will utilize 500 genes to: 1) compare alternate approaches to the reconstruction of species trees using a robust sample of genetic data, 2) resolve problematic systematic relationships within Delphinidae (oceanic dolphins), Phocoenidae (porpoises), and Balaenopteroidea (rorquals and gray whale), 3) synthesize a phylogenomic blueprint for modern cetaceans. Exon capture and next generation sequencing methods will be employed to rapidly characterize candidate loci that represent genes predicted to have undergone adaptive or degenerative change. The researchers will target genes that are critical for behavioral and anatomical features that are highly derived in the group, including loci implicated in vision, hearing, olfaction, deep diving, aging, tooth development, baleen formation, and brain size. The end result will be the first, detailed, genomic characterization of a major macroevolutionary transition that is also documented by extensive fossil evidence.