List of contributors; Richard R. Hudson: Gene genealogies and the coalescent process; John C. Avise & R. Martin Ball, Jr: Principles of genealogical concordance in species concepts and biological taxonomy; Richard C. Harrison: Hybrid zones: windows on evolutionary process; Hampton L. Carson: Evolutionary process as studied in population genetics: clues from phylogeny; Michael J. Ryan: Sexual selection, sensory systems, and sensory exploitation; M.W. Shaw & G.M. Hewitt: B chromosomes, selfish DNA, and theoretical models: where next?; D. Couvet, A. Atlan, E. Belhassen, C. Gliddon, P.H. Gouyon, & F. Kjellberg: Coevolution between two symbionts: the case of cytoplasmic male-sterility in higher plants; Albert F. Bennett & Raymond B. Huey: Studying the evolution of physiological performance; May R. Berenbaum: Plant consumers and plant secondary chemistry: past, present and future; Index; Content lists of previous volumes.