The genetic changes that produce speciation have fascinated researchers for many years. To date, most research on this crucial aspect of evolution has taken a retrospective approach that I call the spyglass. However, population-level analysis of the ecological and genetic mechanisms that produce reproductive isolation between partially isolated ecotypes or races (the magnifying glass) can provide a very different perspective on the problem of speciation. Both the spyglass and the magnifying glass are useful tools in the genetic analysis of speciation; any truly general theory of how speciation occurs must be consistent not only with observations from fully differentiated species, but also with mechanisms seen at the population level in partially isolated ecological races. Speciation is a multidimensional problem, and we will not solve Darwin’s mystery unless we scrutinize it from every possible vantage point.
I thank John Avise and Francisco Ayala for the invitation to discuss these ideas at the Sackler Colloquium; Dolph Schluter and an anonymous referee for exceptionally thoughtful comments on the manuscript; Gina Conte for developing the multiplexed microsatellites for the new linkage map; Justin Malin for some clever computational assistance; and Casey Mason-Foley, Kelly Mills, and Jeffrey Lew for PCRs without end. My work on speciation is supported by National Science Foundation Grants DEB9796222, DEB0221221, and DEB0528288 and the U.S. Department of Agriculture National Research Initiative, Gateways to Genomics Program.