Department of Biosciences, Rice University, Houston, Texas, United States of America.|Department of Biosciences, Rice University, Houston, Texas, United States of America.|Department of Biosciences, Rice University, Houston, Texas, United States of America.|Department of Biosciences, Rice University, Houston, Texas, United States of America.|Department of Mathematics, University of Houston, Houston, Texas, United States of America.|Department of Mathematics, University of Houston, Houston, Texas, United States of America.|Department of Biosciences, Rice University, Houston, Texas, United States of America.