Sixteen volumes and one supplement have now appeared in the series known as Evolutionary Biology. The editors continue to seek critical re­ views, original papers, and commentaries on controversial topics. It is our aim to publish papers primarily of greater length and depth than those normally published by society journals and quarterlies. The editors make every attempt to solicit manuscripts on an international scale and to see that every facet of evolutionary biology-classical or modern-is cov­ ered. Manuscripts should be sent to anyone of the following: Max K. Hecht, Department of Biology, Queens College of the City University of New York, Flushing, New York 11367; Bruce Wallace, Department of Biology, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061; Ghillean T. Prance, New York Botanical Garden, Bronx, New York 10458. The Editors vii Contents 1. Darwinian Selection of Self-Replicating RNA Molecules 1 Christ(~r K. Biehricher Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Replication of Virus RNA in Vitro. . . . . . . . . . . . . . . . . . . . . . . . 2 Extracellular Darwinian Experiments. . . . . . . . . . . . . . . . . . . . . . 5 Characterization of the QI3 Replicase. . . . . . . . . . . . . . . . . . . . . . 9 Nonviral RNA Templates of QI3 Replicase. . . . . . . . . . . . . . . . . . II The Mechanism of RNA Replication . . . . . . . . . . . . . . . . . . . . . . 14 Initiation of Replication and Template Specificity . . . . . . . . . . . 14 Mechanism of Replica Chain Elongation. . . . . . . . . . . . . . . . . . 17 Termination of Replication. . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Replication of RNA Variants . . . . . . . . . . . . . . . . . . . . . . . . . . 21 TheQuasispecies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 De NOl'O Synthesis of Self-Replicating RNA. . . . . . . . . . . . . . . . . 27 The Mechanism of Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 Selection in the Exponential Growth Phase. . . . . . . . . . . . . . . . 32 Selection in the Linear Growth Phase. . . . . . . . . . . . . . . . . . . . 35 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 Appendix I. Replication. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 Appendix II. The Quasispecies. . . . . . . . . . . . . . . . . . . . . . . . . . . 43 Appendix III. Selection under Various Conditions . . . . . . . . . . . . 44 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .