RESEARCH ARTICLE Reproductive Mode and the Evolution of Genome Size and Structure in Caenorhabditis Nematodes Janna L. Fierst1¤a, John H. Willis1, Cristel G. Thomas2, Wei Wang2, Rose M. Reynolds1¤b, Timothy E. Ahearne1, Asher D. Cutter2, Patrick C. Phillips1* 1 Institute of Ecology and Evolution, University of Oregon, Eugene, Oregon, United States of America, 2 Department of Ecology and Evolutionary Biology and Centre for the Analysis of Genome Evolution and Function, University of Toronto, Ontario, Canada a11111 ¤a Current Address: Department of Biological Sciences, The University of Alabama, Tuscaloosa, Alabama, USA ¤b Current Address: Department of Biology, William Jewell College, Liberty, Missouri USA *
[email protected] Abstract OPEN ACCESS Citation: Fierst JL, Willis JH, Thomas CG, Wang W, The self-fertile nematode worms Caenorhabditis elegans, C. briggsae, and C. tropicalis Reynolds RM, Ahearne TE, et al. (2015) evolved independently from outcrossing male-female ancestors and have genomes 20- Reproductive Mode and the Evolution of Genome 40% smaller than closely related outcrossing relatives. This pattern of smaller genomes for Size and Structure in Caenorhabditis Nematodes. PLoS Genet 11(6): e1005323. doi:10.1371/journal. selfing species and larger genomes for closely related outcrossing species is also seen in pgen.1005323 plants. We use comparative genomics, including the first high quality genome assembly for Editor: Mark Blaxter, University of Edinburgh, an outcrossing member of the genus (C. remanei) to test several hypotheses for the evolu- UNITED KINGDOM tion of genome reduction under a change in mating system. Unlike plants, it does not appear Received: July 29, 2014 that reductions in the number of repetitive elements, such as transposable elements, are an important contributor to the change in genome size.